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Tue, 22 Sep 2020 21:53:53 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKqEE-0005aY-In for linux-arm-kernel@lists.infradead.org; Tue, 22 Sep 2020 21:53:40 +0000 Received: from localhost.localdomain (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id B3E6920B36E7; Tue, 22 Sep 2020 14:53:35 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com B3E6920B36E7 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600811617; bh=nDFEfQDC2lbLTYnGJ2HCgyGbCrVZr82PA/GetuDWHoY=; h=From:To:Subject:Date:In-Reply-To:References:From; b=WG0qfkCX3mN+TcFDmNFXTXji0kf0wjOy3CUhpFO7hUKbAxGt8Qj7qQ5I3S22uGZdQ E0ZnSN7TIoR6GNPSDZS+IsiZmJTPUHJlATRZbvUTR7b/3WIbdaWK0kOBuMXKqut8W5 0aqokugTkazpsTOyOF2mhXnwEeWWEFzp4EzNeOzg= From: madvenka@linux.microsoft.com To: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, luto@kernel.org, David.Laight@ACULAB.COM, fweimer@redhat.com, mark.rutland@arm.com, mic@digikod.net, pavel@ucw.cz, madvenka@linux.microsoft.com Subject: [PATCH v2 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API Date: Tue, 22 Sep 2020 16:53:23 -0500 Message-Id: <20200922215326.4603-2-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200922215326.4603-1-madvenka@linux.microsoft.com> References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200922215326.4603-1-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200922_175338_732311_CD44A56B X-CRM114-Status: GOOD ( 40.12 ) X-Spam-Score: -17.9 (-----------------) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-17.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [13.77.154.182 listed in list.dnswl.org] -7.5 USER_IN_DEF_SPF_WL From: address is in the default SPF white-list -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.5 ENV_AND_HDR_SPF_MATCH Env and Hdr From used in default SPF WL Match X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: "Madhavan T. Venkataraman" Introduction ============ Dynamic code is used in many different user applications. Dynamic code is often generated at runtime. Dynamic code can also just be a pre-defined sequence of machine instructions in a data buffer. Examples of dynamic code are trampolines, JIT code, DBT code, etc. Dynamic code is placed either in a data page or in a stack page. In order to execute dynamic code, the page it resides in needs to be mapped with execute permissions. Writable pages with execute permissions provide an attack surface for hackers. Attackers can use this to inject malicious code, modify existing code or do other harm. To mitigate this, LSMs such as SELinux implement W^X. That is, they may not allow pages to have both write and execute permissions. This prevents dynamic code from executing and blocks applications that use it. To allow genuine applications to run, exceptions have to be made for them (by setting execmem, etc) which opens the door to security issues. The W^X implementation today is not complete. There exist many user level tricks that can be used to load and execute dynamic code. E.g., - Load the code into a file and map the file with R-X. - Load the code in an RW- page. Change the permissions to R--. Then, change the permissions to R-X. - Load the code in an RW- page. Remap the page with R-X to get a separate mapping to the same underlying physical page. IMO, these are all security holes as an attacker can exploit them to inject his own code. In the future, these holes will definitely be closed. For instance, LSMs (such as the IPE proposal [1]) may only allow code in properly signed object files to be mapped with execute permissions. This will do two things: - user level tricks using anonymous pages will fail as anonymous pages have no file identity - loading the code in a temporary file and mapping it with R-X will fail as the temporary file would not have a signature We need a way to execute such code without making security exceptions. Trampolines are a good example of dynamic code. A couple of examples of trampolines are given below. My first use case for this RFC is libffi. Solution ======== The solution is to convert dynamic code to static code and place it in a source file. The binary generated from the source can be signed. The kernel can use signature verification to authenticate the binary and allow the code to be mapped and executed. The problem is that the static code has to be able to find the data that it needs when it executes. For functions, the ABI defines the way to pass parameters. But, for arbitrary dynamic code, there isn't a standard ABI compliant way to pass data to the code for most architectures. Each instance of dynamic code defines its own way. For instance, co-location of code and data and PC-relative data referencing are used in cases where the ISA supports it. We need one standard way that would work for all architectures and ABIs. The solution has two parts: 1. The maintainer of the code writes the static code assuming that the data needed by the code is already pointed to by a designated register. 2. The kernel supplies a small universal trampoline that does the following: - Load the address of the data in a designated register - Load the address of the static code in a designated register - Jump to the static code User code would use a kernel supplied API to create and map the trampoline. The address values would be baked into the code so that no special ISA features are needed. To conserve memory, the kernel will pack as many trampolines as possible in a page and provide a trampoline table to user code. The table itself is managed by the user. Kernel API ========== A kernel API based on anonymous file descriptors is defined to create trampolines. The following sections describe the API. Create trampfd ============== This feature introduces a new trampfd system call. struct trampfd_info info; int trampfd; trampfd = syscall(440, &info); The kernel creates a trampoline file object and returns the following items in info: ntrampolines The number of trampolines that can be created with one trampfd. The user may create fewer trampolines if he wishes. code_size The size of each trampoline. code_offset The file offset to be used in mmap() to map the trampoline code. Initialize trampfd ================== A trampfd is initialized in this manner: struct trampfd_code code; struct trampfd_data data; /* * Code descriptor. */ code.ntrampolines = number of desired trampolines; code.reg = code register name; code.table = array of code addresses /* * Data descriptor. */ data.reg = data register name; data.table = array of data addresses pwrite(trampfd, &code, sizeof(init), TRAMPFD_CODE); pwrite(trampfd, &data, sizeof(init), TRAMPFD_DATA); The register names are defined in ptrace.h (reg_32_name and reg_64_name). It is recommended that the code descriptor and code array be placed in the .rodata section so that an attacker cannot modify its contents. Instead of pwrite(), the user can also do lseek() and write(). Map trampfd =========== The user uses mmap() to map the trampoline table into user address space. len = info.code_size * code.ntrampolines; prot = PROT_READ | PROT_EXEC; flags = MAP_PRIVATE; offset = info.code_offset; trampoline_table = mmap(NULL, len, prot, flags, trampfd, offset); The kernel generates the trampoline table. The code for trampoline X in the table is: load &code_table[X], code_reg load (code_reg), code_reg load &data_table[X], data_reg load (data_reg), data_reg jump code_reg Each mmap() will only map a single base page. Large pages are not supported. A trampoline file can only be mmapped once in an address space. Trampoline file mappings cannot be shared across address spaces. So, sending the trampoline file descriptor over a unix domain socket and mapping it in another process will not work. The trampoline code is generated with &code_table[X] and &data_table[X] hard coded in it. But code_table[X] and data_table[X] can be modified by user code dynamically so supply the code and data to trampoline X. Trampoline table management =========================== The user manages the trampoline table. The address of trampoline X is: trampoline_table + info.code_size * X; Prior to invoking trampoline X, the user must initialize code_table[X] and data_table[X]. Unmap trampfd ============= Once the user is done with the trampoline table, it may be unmapped: len = info.code_size * code.ntrampolines; munmap(trampoline_table, len); Remove trampfd ============== To remove the trampfd: close(trampfd); Signed-off-by: Madhavan T. Venkataraman --- fs/Makefile | 1 + fs/trampfd/Makefile | 5 + fs/trampfd/trampfd_fops.c | 241 ++++++++++++++++++++++++++++++ fs/trampfd/trampfd_map.c | 142 ++++++++++++++++++ include/linux/syscalls.h | 2 + include/linux/trampfd.h | 49 ++++++ include/uapi/asm-generic/unistd.h | 4 +- include/uapi/linux/trampfd.h | 184 +++++++++++++++++++++++ init/Kconfig | 7 + kernel/sys_ni.c | 3 + 10 files changed, 637 insertions(+), 1 deletion(-) create mode 100644 fs/trampfd/Makefile create mode 100644 fs/trampfd/trampfd_fops.c create mode 100644 fs/trampfd/trampfd_map.c create mode 100644 include/linux/trampfd.h create mode 100644 include/uapi/linux/trampfd.h diff --git a/fs/Makefile b/fs/Makefile index 2ce5112b02c8..227761302000 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -136,3 +136,4 @@ obj-$(CONFIG_EFIVAR_FS) += efivarfs/ obj-$(CONFIG_EROFS_FS) += erofs/ obj-$(CONFIG_VBOXSF_FS) += vboxsf/ obj-$(CONFIG_ZONEFS_FS) += zonefs/ +obj-$(CONFIG_TRAMPFD) += trampfd/ diff --git a/fs/trampfd/Makefile b/fs/trampfd/Makefile new file mode 100644 index 000000000000..ae09a0b1f841 --- /dev/null +++ b/fs/trampfd/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 + +obj-$(CONFIG_TRAMPFD) += trampfd.o + +trampfd-y += trampfd_fops.o trampfd_map.o diff --git a/fs/trampfd/trampfd_fops.c b/fs/trampfd/trampfd_fops.c new file mode 100644 index 000000000000..7164dd4d9039 --- /dev/null +++ b/fs/trampfd/trampfd_fops.c @@ -0,0 +1,241 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline FD - System call and File operations. + * + * Author: Madhavan T. Venkataraman (madvenka@microsoft.com) + * + * Copyright (C) 2020 Microsoft Corporation. + */ + +#include +#include +#include +#include +#include +#include +#include + +char *trampfd_name = "[trampfd]"; + +struct kmem_cache *trampfd_cache; + +/* + * Arch stub function to return info for the trampfd syscall. + */ +int __attribute__((weak)) trampfd_arch(struct trampfd_info *info) +{ + return -EOPNOTSUPP; +} + +/* + * Arch stub function to do arch specific initialization for a code + * descriptor. + */ +int __attribute__((weak)) trampfd_code_arch(struct trampfd_code *code) +{ + return -EOPNOTSUPP; +} + +/* + * Arch stub function to do arch specific initialization for a data + * descriptor. + */ +int __attribute__((weak)) trampfd_data_arch(struct trampfd_data *data) +{ + return -EOPNOTSUPP; +} + +#ifdef CONFIG_PROC_FS +static void trampfd_show_fdinfo(struct seq_file *sfile, struct file *file) +{ + seq_puts(sfile, "Trampoline FD\n"); +} +#endif + +static loff_t trampfd_llseek(struct file *file, loff_t offset, int whence) +{ + struct trampfd *trampfd = file->private_data; + + if (whence != SEEK_SET) + return -EINVAL; + + if ((offset < 0) || (offset >= TRAMPFD_NUM_OFFSETS)) + return -EINVAL; + + mutex_lock(&trampfd->lock); + if (offset != file->f_pos) { + file->f_pos = offset; + file->f_version = 0; + } + mutex_unlock(&trampfd->lock); + return offset; +} + +int trampfd_code(struct file *file, const char __user *arg, size_t count) +{ + struct trampfd *trampfd = file->private_data; + struct trampfd_code code; + int rc = 0; + + if (count != sizeof(code)) + return -EINVAL; + + if (copy_from_user(&code, arg, sizeof(code))) + return -EFAULT; + + mutex_lock(&trampfd->lock); + + if (trampfd->code) { + rc = -EEXIST; + goto unlock; + } + + rc = trampfd_code_arch(&code); + if (rc) + goto unlock; + + trampfd->code_reg = code.reg; + trampfd->ntrampolines = code.ntrampolines; + trampfd->code = (void *) (uintptr_t) code.table; +unlock: + mutex_unlock(&trampfd->lock); + return rc; +} + +int trampfd_data(struct file *file, const char __user *arg, size_t count) +{ + struct trampfd *trampfd = file->private_data; + struct trampfd_data data; + int rc = 0; + + if (count != sizeof(data)) + return -EINVAL; + + if (copy_from_user(&data, arg, sizeof(data))) + return -EFAULT; + + if (data.reserved) + return -EINVAL; + + mutex_lock(&trampfd->lock); + + if (trampfd->data) { + rc = -EEXIST; + goto unlock; + } + + rc = trampfd_data_arch(&data); + if (rc) + goto unlock; + + trampfd->data_reg = data.reg; + trampfd->data = (void *) (uintptr_t) data.table; +unlock: + mutex_unlock(&trampfd->lock); + return rc; +} + +static ssize_t trampfd_write(struct file *file, const char __user *arg, + size_t count, loff_t *ppos) +{ + int rc; + + if (!arg || !count) + return -EINVAL; + + switch (*ppos) { + case TRAMPFD_CODE: + rc = trampfd_code(file, arg, count); + break; + + case TRAMPFD_DATA: + rc = trampfd_data(file, arg, count); + break; + + default: + rc = -EINVAL; + goto out; + } +out: + return rc ? rc : (ssize_t) count; +} + +static int trampfd_release(struct inode *inode, struct file *file) +{ + struct trampfd *trampfd = file->private_data; + + mutex_destroy(&trampfd->lock); + kmem_cache_free(trampfd_cache, trampfd); + return 0; +} + +const struct file_operations trampfd_fops = { +#ifdef CONFIG_PROC_FS + .show_fdinfo = trampfd_show_fdinfo, +#endif + .llseek = trampfd_llseek, + .write = trampfd_write, + .release = trampfd_release, + .mmap = trampfd_mmap, + .get_unmapped_area = trampfd_get_unmapped_area, +}; + +SYSCALL_DEFINE1(trampfd, struct trampfd_info *, info_arg) +{ + struct trampfd *trampfd; + struct trampfd_info info; + struct file *file; + int fd; + int rc; + + if (!trampfd_cache) + return -ENOMEM; + + if (!info_arg) + return -EINVAL; + + trampfd = kmem_cache_zalloc(trampfd_cache, GFP_KERNEL); + if (!trampfd) + return -ENOMEM; + mutex_init(&trampfd->lock); + trampfd->creator = current->pid; + + trampfd_arch(&info); + + if (copy_to_user(info_arg, &info, sizeof(info))) { + rc = -EFAULT; + goto freetramp; + } + + rc = get_unused_fd_flags(O_CLOEXEC); + if (rc < 0) + goto freetramp; + fd = rc; + + file = anon_inode_getfile(trampfd_name, &trampfd_fops, trampfd, O_RDWR); + if (IS_ERR(file)) { + rc = PTR_ERR(file); + goto freefd; + } + file->f_mode |= (FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE); + + fd_install(fd, file); + return fd; +freefd: + put_unused_fd(fd); +freetramp: + kmem_cache_free(trampfd_cache, trampfd); + return rc; +} + +int __init trampfd_feature_init(void) +{ + trampfd_cache = kmem_cache_create("trampfd_cache", + sizeof(struct trampfd), 0, SLAB_HWCACHE_ALIGN, NULL); + if (trampfd_cache == NULL) { + pr_warn("%s: kmem_cache_create failed", __func__); + return -ENOMEM; + } + return 0; +} +core_initcall(trampfd_feature_init); diff --git a/fs/trampfd/trampfd_map.c b/fs/trampfd/trampfd_map.c new file mode 100644 index 000000000000..679b29768491 --- /dev/null +++ b/fs/trampfd/trampfd_map.c @@ -0,0 +1,142 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline FD - Memory mapping. + * + * Author: Madhavan T. Venkataraman (madvenka@microsoft.com) + * + * Copyright (C) 2020 Microsoft Corporation. + */ + +#include +#include +#include +#include +#include +#include + +/* + * Arch stub function to populate a page with trampolines based on a + * trampoline specification. + */ +void __attribute__((weak)) trampfd_code_fill(struct trampfd *trampfd, + char *addr) +{ +} + +static void trampfd_close(struct vm_area_struct *vma) +{ + struct trampfd *trampfd = vma->vm_file->private_data; + + mutex_lock(&trampfd->lock); + + if (trampfd->page) { + __free_pages(trampfd->page, 0); + trampfd->page = NULL; + } + trampfd->mapped = false; + + mutex_unlock(&trampfd->lock); +} + +static vm_fault_t trampfd_fault(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + struct trampfd *trampfd = vma->vm_file->private_data; + struct page *new_page = NULL; + void *addr; + + /* + * Check this outside the lock so the lock does not have to be + * dropped in order to allocate a page. Races are benign. + */ + if (!trampfd->page) { + new_page = alloc_pages(GFP_KERNEL, 0); + if (!new_page) + return VM_FAULT_OOM; + } + + mutex_lock(&trampfd->lock); + + if (!trampfd->page) { + trampfd->page = new_page; + new_page = NULL; + /* + * Populate the page with trampolines. + */ + addr = kmap(trampfd->page); + trampfd_code_fill(trampfd, addr); + kunmap(trampfd->page); + } + vmf->page = trampfd->page; + get_page(vmf->page); + + mutex_unlock(&trampfd->lock); + + if (new_page) + __free_pages(new_page, 0); + return 0; +} + +static const struct vm_operations_struct trampfd_vm_ops = { + .close = trampfd_close, + .fault = trampfd_fault, +}; + +int trampfd_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct trampfd *trampfd = vma->vm_file->private_data; + int rc = 0; + + /* + * A trampfd cannot be mapped into multiple address spaces. + */ + if (current->pid != trampfd->creator) + return -EINVAL; + + mutex_lock(&trampfd->lock); + + /* + * trampfd must be initialized before it can be mapped. + */ + if (!trampfd->code || !trampfd->data) { + rc = -EINVAL; + goto unlock; + } + + /* + * A trampfd cannot be mapped multiple times in the same address space. + */ + if (trampfd->mapped) { + rc = -EEXIST; + goto unlock; + } + + /* + * prot should be R-X. + */ + if ((vma->vm_flags & VM_WRITE) || !(vma->vm_flags & VM_READ) || + !(vma->vm_flags & VM_EXEC)) { + rc = -EINVAL; + goto unlock; + } + trampfd->mapped = true; + vma->vm_ops = &trampfd_vm_ops; +unlock: + mutex_unlock(&trampfd->lock); + return rc; +} + +unsigned long +trampfd_get_unmapped_area(struct file *file, unsigned long orig_addr, + unsigned long len, unsigned long pgoff, + unsigned long flags) +{ + const typeof_member(struct file_operations, get_unmapped_area) + get_area = current->mm->get_unmapped_area; + + if (pgoff != TRAMPFD_CODE_PGOFF || flags != MAP_PRIVATE || + len != PAGE_SIZE) + return -EINVAL; + + return get_area(file, orig_addr, len, pgoff, flags); +} diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index b951a87da987..91f55ff3cdac 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -69,6 +69,7 @@ union bpf_attr; struct io_uring_params; struct clone_args; struct open_how; +struct trampfd_info; #include #include @@ -1005,6 +1006,7 @@ asmlinkage long sys_pidfd_send_signal(int pidfd, int sig, siginfo_t __user *info, unsigned int flags); asmlinkage long sys_pidfd_getfd(int pidfd, int fd, unsigned int flags); +asmlinkage long sys_trampfd(struct trampfd_info *info); /* * Architecture-specific system calls diff --git a/include/linux/trampfd.h b/include/linux/trampfd.h new file mode 100644 index 000000000000..c98fa1741c36 --- /dev/null +++ b/include/linux/trampfd.h @@ -0,0 +1,49 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Trampoline FD - Internal structures and definitions. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ +#ifndef _LINUX_TRAMPFD_H +#define _LINUX_TRAMPFD_H + +#include + +/* + * mmap() offsets. + */ +enum trampfd_pgoff { + TRAMPFD_CODE_PGOFF = 1, + TRAMPFD_NUM_PGOFF, +}; + +/* + * Trampoline structure. + */ +struct trampfd { + struct mutex lock; /* to serialize access */ + pid_t creator; /* to prevent sharing */ + + short code_reg; /* code register name */ + short data_reg; /* data register name */ + int ntrampolines; /* number of trampolines */ + + void *code; /* user code address table */ + void *data; /* user data address table */ + + struct page *page; /* code page */ + bool mapped; /* mapped into address space? */ +}; + +#ifdef CONFIG_TRAMPFD + +int trampfd_mmap(struct file *file, struct vm_area_struct *vma); +unsigned long trampfd_get_unmapped_area(struct file *file, unsigned long addr, + unsigned long len, unsigned long pgoff, + unsigned long flags); + +#endif /* CONFIG_TRAMPFD */ + +#endif /* _LINUX_TRAMPFD_H */ diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index f4a01305d9a6..3b1ad4b75c7a 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -857,9 +857,11 @@ __SYSCALL(__NR_openat2, sys_openat2) __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd) #define __NR_faccessat2 439 __SYSCALL(__NR_faccessat2, sys_faccessat2) +#define __NR_trampfd 440 +__SYSCALL(__NR_trampfd, sys_trampfd) #undef __NR_syscalls -#define __NR_syscalls 440 +#define __NR_syscalls 441 /* * 32 bit systems traditionally used different diff --git a/include/uapi/linux/trampfd.h b/include/uapi/linux/trampfd.h new file mode 100644 index 000000000000..9bbc0450e16d --- /dev/null +++ b/include/uapi/linux/trampfd.h @@ -0,0 +1,184 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/* + * Trampoline FD - API structures and definitions. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ +#ifndef _UAPI_LINUX_TRAMPFD_H +#define _UAPI_LINUX_TRAMPFD_H + +#include +#include + +/* + * All structure fields are defined so that they are the same width and at the + * same structure offset on 32-bit and 64-bit to avoid compat code. + * + * All fields named "reserved" must be set to 0. They are there primarily for + * alignment. But they may be used in the future. + */ + +/* ---------------------------- Trampfd Feature --------------------------- */ + +/* + * This feature can be used to help convert dynamic user code to static user + * code so that the code can be in the text segment of a binary file. This + * allows the kernel to authenticate the code. E.g., using signature + * verification of the binary file. + * + * The problem in converting dynamic code to static code is that the static + * code needs to be able to locate its data dynamically. So, its data needs + * to be loaded in a designated register before jumping to the static code. + * + * This feature uses the kernel to generate a small, secure trampoline to do + * this. The trampoline code looks like this: + * + * - load the address of the static code in a register (code_reg) + * - load the address of its data in a register (data_reg) + * - jump to code_reg + * + * The kernel places the trampoline in a user page and maps it into the user + * address space. To conserve memory, the kernel packs multiple trampolines in + * a page and creates a trampoline table. + */ + +/* -------------------------- Trampoline Creation ------------------------- */ + +/* + * This feature introduces a new trampfd system call. + * + * struct trampfd_info info; + * + * trampfd = syscall(430, &info); + * + * The kernel returns the following items in info: + * + * ntrampolines + * The number of trampolines that can be created with one trampfd. The + * user may create fewer trampolines if he wishes. + * + * code_size + * The size of each trampoline. + * + * code_offset + * The file offset to be used in mmap() to map the trampoline code. + */ +struct trampfd_info { + __u32 ntrampolines; + __u32 code_size; + __u32 code_offset; + __u32 reserved; +}; + +/* ----------------------- Trampoline Initialization ---------------------- */ + +/* + * Trampoline code descriptor. + * + * ntrampolines + * User specified number of trampolines. This number cannot exceed + * info.ntrampolines. + * + * reg + * User specified code register name. This is architecture specific and + * can be obtained from ptrace.h. + * + * table + * User array of code addresses, one address per trampoline. + * + */ +struct trampfd_code { + __u32 ntrampolines; + __u32 reg; + __u64 table; +}; + +/* + * Trampoline data descriptor. + * + * reg + * User specified data register name. This is architecture specific and + * can be obtained from ptrace.h. + * + * table + * User array of data addresses, one address per trampoline. + * + */ +struct trampfd_data { + __u32 reg; + __u32 reserved; + __u64 table; +}; + +/* + * A trampfd is initialized in this manner: + * + * struct trampfd_code code; + * struct trampfd_data data; + * + * code.ntrampolines = number of desired trampolines; + * code.reg = code register name; + * code.table = array of code addresses + * + * data.reg = data register name; + * data.table = array of data addresses + * + * pwrite(trampfd, &code, sizeof(init), TRAMPFD_CODE); + * pwrite(trampfd, &data, sizeof(init), TRAMPFD_DATA); + * + * It is recommended that the code descriptor and code array be placed in the + * .rodata section so that an attacker cannot modify its contents. + */ + +/* ---------------------------- Trampoline mapping ------------------------ */ + +/* + * The user uses mmap() to map the trampoline table into user address space. + * + * len = info.code_size * code.ntrampolines; + * prot = PROT_READ | PROT_EXEC; + * flags = MAP_PRIVATE; + * offset = info.code_offset; + * + * trampoline_table = mmap(NULL, len, prot, flags, trampfd, offset); + * + * The kernel generates the trampoline table. The code for trampoline X in the + * table is: + * + * load code_table[X] into code_reg + * load data_table[X] into data_reg + * jump code_reg + * + * The user manages the trampoline table. The address of trampoline X is: + * + * trampoline_table + info.code_size * X; + * + * Prior to invoking trampoline X, the user must initialize code_table[X] and + * data_table[X]. + */ + +/* ------------------------- Symbolic offsets -------------------------- */ + +/* + * trampfd can have different actions/parameters associated with it. Each one + * has a symbolic file offset. Action/Parameter structures are read or written + * at their file offsets. + * + * Offset Operation Data + * ------------------------------------------------------------------------ + * TRAMPFD_CODE Write struct trampfd_code + * TRAMPFD_DATA Write struct trampfd_data + * ------------------------------------------------------------------------ + */ +enum trampfd_offsets { + TRAMPFD_CODE, + TRAMPFD_DATA, + TRAMPFD_NUM_OFFSETS, +}; + + +/* ----------------------------------------------------------------------- */ + +#endif /* _UAPI_LINUX_TRAMPFD_H */ diff --git a/init/Kconfig b/init/Kconfig index 0498af567f70..bb3ecca5b8e7 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2313,3 +2313,10 @@ config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE # . config ARCH_HAS_SYSCALL_WRAPPER def_bool n + +config TRAMPFD + bool "Enable trampfd() system call" + depends on MMU + help + Enable the trampfd() system call that allows a process to map + kernel generated trampolines within its address space. diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index 3b69a560a7ac..93c5972aba85 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -349,6 +349,9 @@ COND_SYSCALL(pkey_mprotect); COND_SYSCALL(pkey_alloc); COND_SYSCALL(pkey_free); +/* Trampoline fd */ +COND_SYSCALL(trampfd); + /* * Architecture specific weak syscall entries. 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Tue, 22 Sep 2020 21:53:55 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKqEF-0005bD-VT for linux-arm-kernel@lists.infradead.org; Tue, 22 Sep 2020 21:53:42 +0000 Received: from localhost.localdomain (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id CE92F20BBF7F; Tue, 22 Sep 2020 14:53:37 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com CE92F20BBF7F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600811619; bh=3qfx1/3d8ADHXgnKcsbkjWTPFHnk11ORotWaBTL6O08=; h=From:To:Subject:Date:In-Reply-To:References:From; b=b/i4TajljKF8fHi0NxIevwUc75F8PxR/aRpgH2bmiCiY6NTom9+g/s8S2C2qrvGhA rTydYkef4fK5iLnZmHDr3EbALEyd7DONz4+hdEk9ErvjwM9CGtdJhmvrasT8Scc95s VmB6LX9WRSGxAEF5mo3n8hQDgm/bZ07U0CHZzuSU= From: madvenka@linux.microsoft.com To: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, luto@kernel.org, David.Laight@ACULAB.COM, fweimer@redhat.com, mark.rutland@arm.com, mic@digikod.net, pavel@ucw.cz, madvenka@linux.microsoft.com Subject: [PATCH v2 2/4] [RFC] x86/trampfd: Provide support for the trampoline file descriptor Date: Tue, 22 Sep 2020 16:53:24 -0500 Message-Id: <20200922215326.4603-3-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200922215326.4603-1-madvenka@linux.microsoft.com> References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200922215326.4603-1-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200922_175340_211347_083FFAF5 X-CRM114-Status: GOOD ( 19.72 ) X-Spam-Score: -17.9 (-----------------) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-17.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [13.77.154.182 listed in list.dnswl.org] -7.5 USER_IN_DEF_SPF_WL From: address is in the default SPF white-list -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.5 ENV_AND_HDR_SPF_MATCH Env and Hdr From used in default SPF WL Match X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: "Madhavan T. Venkataraman" - Define architecture specific register names - Architecture specific functions for: - system call init - code descriptor check - data descriptor check - Fill a page with a trampoline table for: - 32-bit user process - 64-bit user process Signed-off-by: Madhavan T. Venkataraman --- arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/x86/include/uapi/asm/ptrace.h | 38 ++++ arch/x86/kernel/Makefile | 1 + arch/x86/kernel/trampfd.c | 238 +++++++++++++++++++++++++ 5 files changed, 279 insertions(+) create mode 100644 arch/x86/kernel/trampfd.c diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index d8f8a1a69ed1..d4f17806c9ab 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -443,3 +443,4 @@ 437 i386 openat2 sys_openat2 438 i386 pidfd_getfd sys_pidfd_getfd 439 i386 faccessat2 sys_faccessat2 +440 i386 trampfd sys_trampfd diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 78847b32e137..91b37bc4b6f0 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -360,6 +360,7 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common trampfd sys_trampfd # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/arch/x86/include/uapi/asm/ptrace.h b/arch/x86/include/uapi/asm/ptrace.h index 85165c0edafc..b4be362929b3 100644 --- a/arch/x86/include/uapi/asm/ptrace.h +++ b/arch/x86/include/uapi/asm/ptrace.h @@ -9,6 +9,44 @@ #ifndef __ASSEMBLY__ +/* + * These register names are to be used by 32-bit applications. + */ +enum reg_32_name { + x32_min = 0, + x32_eax = x32_min, + x32_ebx, + x32_ecx, + x32_edx, + x32_esi, + x32_edi, + x32_ebp, + x32_max, +}; + +/* + * These register names are to be used by 64-bit applications. + */ +enum reg_64_name { + x64_min = x32_max, + x64_rax = x64_min, + x64_rbx, + x64_rcx, + x64_rdx, + x64_rsi, + x64_rdi, + x64_rbp, + x64_r8, + x64_r9, + x64_r10, + x64_r11, + x64_r12, + x64_r13, + x64_r14, + x64_r15, + x64_max, +}; + #ifdef __i386__ /* this struct defines the way the registers are stored on the stack during a system call. */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index e77261db2391..feb7f4f311fd 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -157,3 +157,4 @@ ifeq ($(CONFIG_X86_64),y) endif obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT) += ima_arch.o +obj-$(CONFIG_TRAMPFD) += trampfd.o diff --git a/arch/x86/kernel/trampfd.c b/arch/x86/kernel/trampfd.c new file mode 100644 index 000000000000..7b812c200d01 --- /dev/null +++ b/arch/x86/kernel/trampfd.c @@ -0,0 +1,238 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline FD - X86 support. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ + +#include +#include + +#define TRAMPFD_CODE_32_SIZE 24 +#define TRAMPFD_CODE_64_SIZE 40 + +static inline bool is_compat(void) +{ + return (IS_ENABLED(CONFIG_X86_32) || + (IS_ENABLED(CONFIG_COMPAT) && test_thread_flag(TIF_ADDR32))); +} + +/* + * trampfd syscall. + */ +void trampfd_arch(struct trampfd_info *info) +{ + if (is_compat()) + info->code_size = TRAMPFD_CODE_32_SIZE; + else + info->code_size = TRAMPFD_CODE_64_SIZE; + info->ntrampolines = PAGE_SIZE / info->code_size; + info->code_offset = TRAMPFD_CODE_PGOFF << PAGE_SHIFT; + info->reserved = 0; +} + +/* + * trampfd code descriptor check. + */ +int trampfd_code_arch(struct trampfd_code *code) +{ + int ntrampolines; + int min, max; + + if (is_compat()) { + min = x32_min; + max = x32_max; + ntrampolines = PAGE_SIZE / TRAMPFD_CODE_32_SIZE; + } else { + min = x64_min; + max = x64_max; + ntrampolines = PAGE_SIZE / TRAMPFD_CODE_64_SIZE; + } + + if (code->reg < min || code->reg >= max) + return -EINVAL; + + if (!code->ntrampolines || code->ntrampolines > ntrampolines) + return -EINVAL; + return 0; +} + +/* + * trampfd data descriptor check. + */ +int trampfd_data_arch(struct trampfd_data *data) +{ + int min, max; + + if (is_compat()) { + min = x32_min; + max = x32_max; + } else { + min = x64_min; + max = x64_max; + } + + if (data->reg < min || data->reg >= max) + return -EINVAL; + return 0; +} + +/* + * X32 register encodings. + */ +static unsigned char reg_32[] = { + 0, /* x32_eax */ + 3, /* x32_ebx */ + 1, /* x32_ecx */ + 2, /* x32_edx */ + 6, /* x32_esi */ + 7, /* x32_edi */ + 5, /* x32_ebp */ +}; + +static void trampfd_code_fill_32(struct trampfd *trampfd, char *addr) +{ + char *eaddr = addr + PAGE_SIZE; + int creg = trampfd->code_reg - x32_min; + int dreg = trampfd->data_reg - x32_min; + u32 *code = trampfd->code; + u32 *data = trampfd->data; + int i; + + for (i = 0; i < trampfd->ntrampolines; i++, code++, data++) { + /* endbr32 */ + addr[0] = 0xf3; + addr[1] = 0x0f; + addr[2] = 0x1e; + addr[3] = 0xfb; + + /* mov code, %creg */ + addr[4] = 0xB8 | reg_32[creg]; /* opcode+reg */ + memcpy(&addr[5], &code, sizeof(u32)); /* imm32 */ + + /* mov (%creg), %creg */ + addr[9] = 0x8B; /* opcode */ + addr[10] = 0x00 | /* MODRM.mode */ + reg_32[creg] << 3 | /* MODRM.reg */ + reg_32[creg]; /* MODRM.r/m */ + + /* mov data, %dreg */ + addr[11] = 0xB8 | reg_32[dreg]; /* opcode+reg */ + memcpy(&addr[12], &data, sizeof(u32)); /* imm32 */ + + /* mov (%dreg), %dreg */ + addr[16] = 0x8B; /* opcode */ + addr[17] = 0x00 | /* MODRM.mode */ + reg_32[dreg] << 3 | /* MODRM.reg */ + reg_32[dreg]; /* MODRM.r/m */ + + /* jmp *%creg */ + addr[18] = 0xff; /* opcode */ + addr[19] = 0xe0 | reg_32[creg]; /* MODRM.r/m */ + + /* nopl (%eax) */ + addr[20] = 0x0f; + addr[21] = 0x1f; + addr[22] = 0x00; + + /* pad to 4-byte boundary */ + memset(&addr[23], 0, TRAMPFD_CODE_32_SIZE - 23); + addr += TRAMPFD_CODE_32_SIZE; + } + memset(addr, 0, eaddr - addr); +} + +/* + * X64 register encodings. + */ +static unsigned char reg_64[] = { + 0, /* x64_rax */ + 3, /* x64_rbx */ + 1, /* x64_rcx */ + 2, /* x64_rdx */ + 6, /* x64_rsi */ + 7, /* x64_rdi */ + 5, /* x64_rbp */ + 8, /* x64_r8 */ + 9, /* x64_r9 */ + 10, /* x64_r10 */ + 11, /* x64_r11 */ + 12, /* x64_r12 */ + 13, /* x64_r13 */ + 14, /* x64_r14 */ + 15, /* x64_r15 */ +}; + +static void trampfd_code_fill_64(struct trampfd *trampfd, char *addr) +{ + char *eaddr = addr + PAGE_SIZE; + int creg = trampfd->code_reg - x64_min; + int dreg = trampfd->data_reg - x64_min; + u64 *code = trampfd->code; + u64 *data = trampfd->data; + int i; + + for (i = 0; i < trampfd->ntrampolines; i++, code++, data++) { + /* endbr64 */ + addr[0] = 0xf3; + addr[1] = 0x0f; + addr[2] = 0x1e; + addr[3] = 0xfa; + + /* movabs code, %creg */ + addr[4] = 0x48 | /* REX.W */ + ((reg_64[creg] & 0x8) >> 3); /* REX.B */ + addr[5] = 0xB8 | (reg_64[creg] & 0x7); /* opcode+reg */ + memcpy(&addr[6], &code, sizeof(u64)); /* imm64 */ + + /* movq (%creg), %creg */ + addr[14] = 0x48 | /* REX.W */ + ((reg_64[creg] & 0x8) >> 1) | /* REX.R */ + ((reg_64[creg] & 0x8) >> 3); /* REX.B */ + addr[15] = 0x8B; /* opcode */ + addr[16] = 0x00 | /* MODRM.mode */ + ((reg_64[creg] & 0x7)) << 3 | /* MODRM.reg */ + ((reg_64[creg] & 0x7)); /* MODRM.r/m */ + + /* movabs data, %dreg */ + addr[17] = 0x48 | /* REX.W */ + ((reg_64[dreg] & 0x8) >> 3); /* REX.B */ + addr[18] = 0xB8 | (reg_64[dreg] & 0x7); /* opcode+reg */ + memcpy(&addr[19], &data, sizeof(u64)); /* imm64 */ + + /* movq (%dreg), %dreg */ + addr[27] = 0x48 | /* REX.W */ + ((reg_64[dreg] & 0x8) >> 1) | /* REX.R */ + ((reg_64[dreg] & 0x8) >> 3); /* REX.B */ + addr[28] = 0x8B; /* opcode */ + addr[29] = 0x00 | /* MODRM.mode */ + ((reg_64[dreg] & 0x7)) << 3 | /* MODRM.reg */ + ((reg_64[dreg] & 0x7)); /* MODRM.r/m */ + + /* jmpq *%creg */ + addr[30] = 0x40 | /* REX.W */ + ((reg_64[creg] & 0x8) >> 3); /* REX.B */ + addr[31] = 0xff; /* opcode */ + addr[32] = 0xe0 | (reg_64[creg] & 0x7); /* MODRM.r/m */ + + /* nopl (%rax) */ + addr[33] = 0x0f; + addr[34] = 0x1f; + addr[35] = 0x00; + + /* pad to 8-byte boundary */ + memset(&addr[36], 0, TRAMPFD_CODE_64_SIZE - 36); + addr += TRAMPFD_CODE_64_SIZE; + } + memset(addr, 0, eaddr - addr); +} + +void trampfd_code_fill(struct trampfd *trampfd, char *addr) +{ + if (is_compat()) + trampfd_code_fill_32(trampfd, addr); + else + trampfd_code_fill_64(trampfd, addr); +} From patchwork Tue Sep 22 21:53:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 11793359 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1FB971668 for ; Tue, 22 Sep 2020 21:54:17 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C0B6920773 for ; Tue, 22 Sep 2020 21:54:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OKnKQ1Md"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="R8hQixnw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0B6920773 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: mail.kernel.org; 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Tue, 22 Sep 2020 21:54:03 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKqEH-0005cR-SS for linux-arm-kernel@lists.infradead.org; Tue, 22 Sep 2020 21:53:47 +0000 Received: from localhost.localdomain (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id DA8CD20C27C2; Tue, 22 Sep 2020 14:53:39 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com DA8CD20C27C2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600811621; bh=7zXFDd5e9gQDRl70elYDzZIUqUSxDlwg1R6LYZvjU+I=; h=From:To:Subject:Date:In-Reply-To:References:From; b=R8hQixnwCw7jKlbVUp2WcLjT2B1eBsMGQhRGCHNCB47lVsvQkkqkE3GV8ZKHy6wm3 vjRjNeec0yvuNQGVTYgEsDBiFlWgGUdbCIl0J/1RtyjlTOyS71ozka1LIzRDkzafYK 4hr5haytbkwGkefRtLhPALrM+xuyoPG5a6DtkxXU= From: madvenka@linux.microsoft.com To: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, luto@kernel.org, David.Laight@ACULAB.COM, fweimer@redhat.com, mark.rutland@arm.com, mic@digikod.net, pavel@ucw.cz, madvenka@linux.microsoft.com Subject: [PATCH v2 3/4] [RFC] arm64/trampfd: Provide support for the trampoline file descriptor Date: Tue, 22 Sep 2020 16:53:25 -0500 Message-Id: <20200922215326.4603-4-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200922215326.4603-1-madvenka@linux.microsoft.com> References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200922215326.4603-1-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200922_175342_083417_45E81D48 X-CRM114-Status: GOOD ( 19.71 ) X-Spam-Score: -17.9 (-----------------) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-17.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [13.77.154.182 listed in list.dnswl.org] -7.5 USER_IN_DEF_SPF_WL From: address is in the default SPF white-list -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.5 ENV_AND_HDR_SPF_MATCH Env and Hdr From used in default SPF WL Match X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: "Madhavan T. Venkataraman" - Define architecture specific register names - Architecture specific functions for: - system call init - code descriptor check - data descriptor check - Fill a page with a trampoline table for: - 32-bit user process - 64-bit user process Signed-off-by: Madhavan T. Venkataraman --- arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 + arch/arm64/include/uapi/asm/ptrace.h | 59 +++++++ arch/arm64/kernel/Makefile | 2 + arch/arm64/kernel/trampfd.c | 244 +++++++++++++++++++++++++++ 5 files changed, 308 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/kernel/trampfd.c diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h index 3b859596840d..b3b2019f8d16 100644 --- a/arch/arm64/include/asm/unistd.h +++ b/arch/arm64/include/asm/unistd.h @@ -38,7 +38,7 @@ #define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5) #define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800) -#define __NR_compat_syscalls 440 +#define __NR_compat_syscalls 441 #endif #define __ARCH_WANT_SYS_CLONE diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h index 6d95d0c8bf2f..c0493c5322d9 100644 --- a/arch/arm64/include/asm/unistd32.h +++ b/arch/arm64/include/asm/unistd32.h @@ -885,6 +885,8 @@ __SYSCALL(__NR_openat2, sys_openat2) __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd) #define __NR_faccessat2 439 __SYSCALL(__NR_faccessat2, sys_faccessat2) +#define __NR_trampfd 440 +__SYSCALL(__NR_trampfd, sys_trampfd) /* * Please add new compat syscalls above this comment and update diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h index 42cbe34d95ce..2778789c1cbe 100644 --- a/arch/arm64/include/uapi/asm/ptrace.h +++ b/arch/arm64/include/uapi/asm/ptrace.h @@ -88,6 +88,65 @@ struct user_pt_regs { __u64 pstate; }; +/* + * These register names are to be used by 32-bit applications. + */ +enum reg_32_name { + arm_min, + arm_r0 = arm_min, + arm_r1, + arm_r2, + arm_r3, + arm_r4, + arm_r5, + arm_r6, + arm_r7, + arm_r8, + arm_r9, + arm_r10, + arm_r11, + arm_r12, + arm_max, +}; + +/* + * These register names are to be used by 64-bit applications. + */ +enum reg_64_name { + arm64_min = arm_max, + arm64_r0 = arm64_min, + arm64_r1, + arm64_r2, + arm64_r3, + arm64_r4, + arm64_r5, + arm64_r6, + arm64_r7, + arm64_r8, + arm64_r9, + arm64_r10, + arm64_r11, + arm64_r12, + arm64_r13, + arm64_r14, + arm64_r15, + arm64_r16, + arm64_r17, + arm64_r18, + arm64_r19, + arm64_r20, + arm64_r21, + arm64_r22, + arm64_r23, + arm64_r24, + arm64_r25, + arm64_r26, + arm64_r27, + arm64_r28, + arm64_r29, + arm64_max, +}; + struct user_fpsimd_state { __uint128_t vregs[32]; __u32 fpsr; diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index a561cbb91d4d..18d373fb1208 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -71,3 +71,5 @@ extra-y += $(head-y) vmlinux.lds ifeq ($(CONFIG_DEBUG_EFI),y) AFLAGS_head.o += -DVMLINUX_PATH="\"$(realpath $(objtree)/vmlinux)\"" endif + +obj-$(CONFIG_TRAMPFD) += trampfd.o diff --git a/arch/arm64/kernel/trampfd.c b/arch/arm64/kernel/trampfd.c new file mode 100644 index 000000000000..3b40ebb12907 --- /dev/null +++ b/arch/arm64/kernel/trampfd.c @@ -0,0 +1,244 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline FD - ARM64 support. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ + +#include +#include +#include + +#define TRAMPFD_CODE_32_SIZE 28 +#define TRAMPFD_CODE_64_SIZE 48 + +static inline bool is_compat(void) +{ + return is_compat_thread(task_thread_info(current)); +} + +/* + * trampfd syscall. + */ +void trampfd_arch(struct trampfd_info *info) +{ + if (is_compat()) + info->code_size = TRAMPFD_CODE_32_SIZE; + else + info->code_size = TRAMPFD_CODE_64_SIZE; + info->ntrampolines = PAGE_SIZE / info->code_size; + info->code_offset = TRAMPFD_CODE_PGOFF << PAGE_SHIFT; + info->reserved = 0; +} + +/* + * trampfd code descriptor check. + */ +int trampfd_code_arch(struct trampfd_code *code) +{ + int ntrampolines; + int min, max; + + if (is_compat()) { + min = arm_min; + max = arm_max; + ntrampolines = PAGE_SIZE / TRAMPFD_CODE_32_SIZE; + } else { + min = arm64_min; + max = arm64_max; + ntrampolines = PAGE_SIZE / TRAMPFD_CODE_64_SIZE; + } + + if (code->reg < min || code->reg >= max) + return -EINVAL; + + if (!code->ntrampolines || code->ntrampolines > ntrampolines) + return -EINVAL; + return 0; +} + +/* + * trampfd data descriptor check. + */ +int trampfd_data_arch(struct trampfd_data *data) +{ + int min, max; + + if (is_compat()) { + min = arm_min; + max = arm_max; + } else { + min = arm64_min; + max = arm64_max; + } + + if (data->reg < min || data->reg >= max) + return -EINVAL; + return 0; +} + +#define MOVARM(ins, reg, imm32) \ +{ \ + u16 *_imm16 = (u16 *) &(imm32); /* little endian */ \ + int _hw, _opcode; \ + \ + for (_hw = 0; _hw < 2; _hw++) { \ + /* movw or movt */ \ + _opcode = _hw ? 0xe3400000 : 0xe3000000; \ + *ins++ = _opcode | (_imm16[_hw] >> 12) << 16 | \ + (reg) << 12 | (_imm16[_hw] & 0xFFF); \ + } \ +} + +#define LDRARM(ins, reg) \ +{ \ + *ins++ = 0xe5900000 | (reg) << 16 | (reg) << 12; \ +} + +#define BXARM(ins, reg) \ +{ \ + *ins++ = 0xe12fff10 | (reg); \ +} + +static void trampfd_code_fill_32(struct trampfd *trampfd, char *addr) +{ + char *eaddr = addr + PAGE_SIZE; + int creg = trampfd->code_reg - arm_min; + int dreg = trampfd->data_reg - arm_min; + u32 *code = trampfd->code; + u32 *data = trampfd->data; + u32 *instruction = (u32 *) addr; + int i; + + for (i = 0; i < trampfd->ntrampolines; i++, code++, data++) { + /* + * movw creg, code & 0xFFFF + * movt creg, code >> 16 + */ + MOVARM(instruction, creg, code); + + /* + * ldr creg, [creg] + */ + LDRARM(instruction, creg); + + /* + * movw dreg, data & 0xFFFF + * movt dreg, data >> 16 + */ + MOVARM(instruction, dreg, data); + + /* + * ldr dreg, [dreg] + */ + LDRARM(instruction, dreg); + + /* + * bx creg + */ + BXARM(instruction, creg); + } + addr = (char *) instruction; + memset(addr, 0, eaddr - addr); +} + +#define MOVQ(ins, reg, imm64) \ +{ \ + u16 *_imm16 = (u16 *) &(imm64); /* little endian */ \ + int _hw, _opcode; \ + \ + for (_hw = 0; _hw < 4; _hw++) { \ + /* movz or movk */ \ + _opcode = _hw ? 0xf2800000 : 0xd2800000; \ + *ins++ = _opcode | _hw << 21 | _imm16[_hw] << 5 | (reg);\ + } \ +} + +#define LDR(ins, reg) \ +{ \ + *ins++ = 0xf9400000 | (reg) << 5 | (reg); \ +} + +#define BR(ins, reg) \ +{ \ + *ins++ = 0xd61f0000 | (reg) << 5; \ +} + +#define PAD(ins) \ +{ \ + while ((uintptr_t) ins & 7) \ + *ins++ = 0; \ +} + +static void trampfd_code_fill_64(struct trampfd *trampfd, char *addr) +{ + char *eaddr = addr + PAGE_SIZE; + int creg = trampfd->code_reg - arm64_min; + int dreg = trampfd->data_reg - arm64_min; + u64 *code = trampfd->code; + u64 *data = trampfd->data; + u32 *instruction = (u32 *) addr; + int i; + + for (i = 0; i < trampfd->ntrampolines; i++, code++, data++) { + /* + * Pseudo instruction: + * + * movq creg, code + * + * Actual instructions: + * + * movz creg, code & 0xFFFF + * movk creg, (code >> 16) & 0xFFFF, lsl 16 + * movk creg, (code >> 32) & 0xFFFF, lsl 32 + * movk creg, (code >> 48) & 0xFFFF, lsl 48 + */ + MOVQ(instruction, creg, code); + + /* + * ldr creg, [creg] + */ + LDR(instruction, creg); + + /* + * Pseudo instruction: + * + * movq dreg, data + * + * Actual instructions: + * + * movz dreg, data & 0xFFFF + * movk dreg, (data >> 16) & 0xFFFF, lsl 16 + * movk dreg, (data >> 32) & 0xFFFF, lsl 32 + * movk dreg, (data >> 48) & 0xFFFF, lsl 48 + */ + MOVQ(instruction, dreg, data); + + /* + * ldr dreg, [dreg] + */ + LDR(instruction, dreg); + + /* + * br creg + */ + BR(instruction, creg); + + /* + * Pad to 8-byte boundary + */ + PAD(instruction); + } + addr = (char *) instruction; + memset(addr, 0, eaddr - addr); +} + +void trampfd_code_fill(struct trampfd *trampfd, char *addr) +{ + if (is_compat()) + trampfd_code_fill_32(trampfd, addr); + else + trampfd_code_fill_64(trampfd, addr); +} From patchwork Tue Sep 22 21:53:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 11793363 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5DDAD59D for ; Tue, 22 Sep 2020 21:55:30 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 30B9620578 for ; Tue, 22 Sep 2020 21:55:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="W3S6g0RM"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="IYCw8eGI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30B9620578 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: mail.kernel.org; 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Tue, 22 Sep 2020 21:53:58 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKqEJ-0005bD-3T for linux-arm-kernel@lists.infradead.org; Tue, 22 Sep 2020 21:53:47 +0000 Received: from localhost.localdomain (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id ABB0920C27C5; Tue, 22 Sep 2020 14:53:41 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com ABB0920C27C5 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600811622; bh=b+dZfSYt921SZbqVi9d6jmG8B2GKXdUDhoo8NhJxV+k=; h=From:To:Subject:Date:In-Reply-To:References:From; b=IYCw8eGIRinivB/mke9s56rfh0IoShsw0x+m1MrlH+ClEZT172gdzHmTznyb90Tlq /1NbC1bWq19USuqC8IvAY4OPuW/L8149bG3rog5kNBYVZ9KhWZPbVxueJG13qcFrzs gI20WK9s0lJaLwaZgnXOuao31fv/Ggt1KRH+IYYM= From: madvenka@linux.microsoft.com To: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, luto@kernel.org, David.Laight@ACULAB.COM, fweimer@redhat.com, mark.rutland@arm.com, mic@digikod.net, pavel@ucw.cz, madvenka@linux.microsoft.com Subject: [PATCH v2 4/4] [RFC] arm/trampfd: Provide support for the trampoline file descriptor Date: Tue, 22 Sep 2020 16:53:26 -0500 Message-Id: <20200922215326.4603-5-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200922215326.4603-1-madvenka@linux.microsoft.com> References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200922215326.4603-1-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200922_175343_502830_1AF481F6 X-CRM114-Status: GOOD ( 17.74 ) X-Spam-Score: -17.9 (-----------------) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-17.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [13.77.154.182 listed in list.dnswl.org] -7.5 USER_IN_DEF_SPF_WL From: address is in the default SPF white-list -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.5 ENV_AND_HDR_SPF_MATCH Env and Hdr From used in default SPF WL Match X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: "Madhavan T. Venkataraman" - Define architecture specific register names - Architecture specific functions for: - system call init - code descriptor check - data descriptor check - Fill a page with a trampoline table, Signed-off-by: Madhavan T. Venkataraman --- arch/arm/include/uapi/asm/ptrace.h | 21 +++++ arch/arm/kernel/Makefile | 1 + arch/arm/kernel/trampfd.c | 124 +++++++++++++++++++++++++++++ arch/arm/tools/syscall.tbl | 1 + 4 files changed, 147 insertions(+) create mode 100644 arch/arm/kernel/trampfd.c diff --git a/arch/arm/include/uapi/asm/ptrace.h b/arch/arm/include/uapi/asm/ptrace.h index e61c65b4018d..598047768f9b 100644 --- a/arch/arm/include/uapi/asm/ptrace.h +++ b/arch/arm/include/uapi/asm/ptrace.h @@ -151,6 +151,27 @@ struct pt_regs { #define ARM_r0 uregs[0] #define ARM_ORIG_r0 uregs[17] +/* + * These register names are to be used by 32-bit applications. + */ +enum reg_32_name { + arm_min, + arm_r0 = arm_min, + arm_r1, + arm_r2, + arm_r3, + arm_r4, + arm_r5, + arm_r6, + arm_r7, + arm_r8, + arm_r9, + arm_r10, + arm_r11, + arm_r12, + arm_max, +}; + /* * The size of the user-visible VFP state as seen by PTRACE_GET/SETVFPREGS * and core dumps. diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 89e5d864e923..652c54c2f19a 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -105,5 +105,6 @@ obj-$(CONFIG_SMP) += psci_smp.o endif obj-$(CONFIG_HAVE_ARM_SMCCC) += smccc-call.o +obj-$(CONFIG_TRAMPFD) += trampfd.o extra-y := $(head-y) vmlinux.lds diff --git a/arch/arm/kernel/trampfd.c b/arch/arm/kernel/trampfd.c new file mode 100644 index 000000000000..45146ed489e8 --- /dev/null +++ b/arch/arm/kernel/trampfd.c @@ -0,0 +1,124 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Trampoline FD - ARM support. + * + * Author: Madhavan T. Venkataraman (madvenka@linux.microsoft.com) + * + * Copyright (c) 2020, Microsoft Corporation. + */ + +#include +#include + +#define TRAMPFD_CODE_SIZE 28 + +/* + * trampfd syscall. + */ +void trampfd_arch(struct trampfd_info *info) +{ + info->code_size = TRAMPFD_CODE_SIZE; + info->ntrampolines = PAGE_SIZE / info->code_size; + info->code_offset = TRAMPFD_CODE_PGOFF << PAGE_SHIFT; + info->reserved = 0; +} + +/* + * trampfd code descriptor check. + */ +int trampfd_code_arch(struct trampfd_code *code) +{ + int ntrampolines; + int min, max; + + min = arm_min; + max = arm_max; + ntrampolines = PAGE_SIZE / TRAMPFD_CODE_SIZE; + + if (code->reg < min || code->reg >= max) + return -EINVAL; + + if (!code->ntrampolines || code->ntrampolines > ntrampolines) + return -EINVAL; + return 0; +} + +/* + * trampfd data descriptor check. + */ +int trampfd_data_arch(struct trampfd_data *data) +{ + int min, max; + + min = arm_min; + max = arm_max; + + if (data->reg < min || data->reg >= max) + return -EINVAL; + return 0; +} + +#define MOVW(ins, reg, imm32) \ +{ \ + u16 *_imm16 = (u16 *) &(imm32); /* little endian */ \ + int _hw, _opcode; \ + \ + for (_hw = 0; _hw < 2; _hw++) { \ + /* movw or movt */ \ + _opcode = _hw ? 0xe3400000 : 0xe3000000; \ + *ins++ = _opcode | (_imm16[_hw] >> 12) << 16 | \ + (reg) << 12 | (_imm16[_hw] & 0xFFF); \ + } \ +} + +#define LDR(ins, reg) \ +{ \ + *ins++ = 0xe5900000 | (reg) << 16 | (reg) << 12; \ +} + +#define BX(ins, reg) \ +{ \ + *ins++ = 0xe12fff10 | (reg); \ +} + +void trampfd_code_fill(struct trampfd *trampfd, char *addr) +{ + char *eaddr = addr + PAGE_SIZE; + int creg = trampfd->code_reg - arm_min; + int dreg = trampfd->data_reg - arm_min; + u32 *code = trampfd->code; + u32 *data = trampfd->data; + u32 *instruction = (u32 *) addr; + int i; + + for (i = 0; i < trampfd->ntrampolines; i++, code++, data++) { + /* + * movw creg, code & 0xFFFF + * movt creg, code >> 16 + */ + MOVW(instruction, creg, code); + + /* + * ldr creg, [creg] + */ + LDR(instruction, creg); + + /* + * movw dreg, data & 0xFFFF + * movt dreg, data >> 16 + */ + MOVW(instruction, dreg, data); + + /* + * ldr dreg, [dreg] + */ + LDR(instruction, dreg); + + /* + * bx creg + */ + BX(instruction, creg); + } + addr = (char *) instruction; + memset(addr, 0, eaddr - addr); +} diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index d5cae5ffede0..85dcbc9e08ee 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -452,3 +452,4 @@ 437 common openat2 sys_openat2 438 common pidfd_getfd sys_pidfd_getfd 439 common faccessat2 sys_faccessat2 +440 common trampfd sys_trampfd