From patchwork Tue Jul 11 11:25:43 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Gladkov X-Patchwork-Id: 13308433 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26E10C00528 for ; Tue, 11 Jul 2023 11:29:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232147AbjGKL3D (ORCPT ); Tue, 11 Jul 2023 07:29:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232011AbjGKL2i (ORCPT ); Tue, 11 Jul 2023 07:28:38 -0400 Received: from us-smtp-delivery-44.mimecast.com (unknown [207.211.30.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42C6B1BCB for ; Tue, 11 Jul 2023 04:28:27 -0700 (PDT) Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-349-1yjghznhNHO9f6zghBUlhw-1; Tue, 11 Jul 2023 07:26:39 -0400 X-MC-Unique: 1yjghznhNHO9f6zghBUlhw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4F71B3C13928; Tue, 11 Jul 2023 11:26:38 +0000 (UTC) Received: from localhost.localdomain.com (unknown [10.45.225.44]) by smtp.corp.redhat.com (Postfix) with ESMTP id C5A9463F3C; Tue, 11 Jul 2023 11:26:25 +0000 (UTC) From: Alexey Gladkov To: LKML , Arnd Bergmann , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk Cc: Palmer Dabbelt , James.Bottomley@HansenPartnership.com, acme@kernel.org, alexander.shishkin@linux.intel.com, axboe@kernel.dk, benh@kernel.crashing.org, borntraeger@de.ibm.com, bp@alien8.de, catalin.marinas@arm.com, christian@brauner.io, dalias@libc.org, davem@davemloft.net, deepa.kernel@gmail.com, deller@gmx.de, dhowells@redhat.com, fenghua.yu@intel.com, firoz.khan@linaro.org, fweimer@redhat.com, geert@linux-m68k.org, glebfm@altlinux.org, gor@linux.ibm.com, hare@suse.com, heiko.carstens@de.ibm.com, hpa@zytor.com, ink@jurassic.park.msu.ru, jhogan@kernel.org, kim.phillips@arm.com, ldv@altlinux.org, linux-alpha@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux@armlinux.org.uk, linuxppc-dev@lists.ozlabs.org, luto@kernel.org, mattst88@gmail.com, mingo@redhat.com, monstr@monstr.eu, mpe@ellerman.id.au, namhyung@kernel.org, paul.burton@mips.com, paulus@samba.org, peterz@infradead.org, ralf@linux-mips.org, rth@twiddle.net, schwidefsky@de.ibm.com, sparclinux@vger.kernel.org, stefan@agner.ch, tglx@linutronix.de, tony.luck@intel.com, tycho@tycho.ws, will@kernel.org, x86@kernel.org, ysato@users.sourceforge.jp Subject: [PATCH v3 2/5] fs: Add fchmodat4() Date: Tue, 11 Jul 2023 13:25:43 +0200 Message-Id: In-Reply-To: References: <87o8pscpny.fsf@oldenburg2.str.redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Palmer Dabbelt On the userspace side fchmodat(3) is implemented as a wrapper function which implements the POSIX-specified interface. This interface differs from the underlying kernel system call, which does not have a flags argument. Most implementations require procfs [1][2]. There doesn't appear to be a good userspace workaround for this issue but the implementation in the kernel is pretty straight-forward. The new fchmodat4() syscall allows to pass the AT_SYMLINK_NOFOLLOW flag, unlike existing fchmodat. [1] https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/fchmodat.c;h=17eca54051ee28ba1ec3f9aed170a62630959143;hb=a492b1e5ef7ab50c6fdd4e4e9879ea5569ab0a6c#l35 [2] https://git.musl-libc.org/cgit/musl/tree/src/stat/fchmodat.c?id=718f363bc2067b6487900eddc9180c84e7739f80#n28 Signed-off-by: Palmer Dabbelt Signed-off-by: Alexey Gladkov Acked-by: Arnd Bergmann --- fs/open.c | 18 ++++++++++++++---- include/linux/syscalls.h | 2 ++ 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/fs/open.c b/fs/open.c index 4478adcc4f3a..58bb88c6afb6 100644 --- a/fs/open.c +++ b/fs/open.c @@ -671,11 +671,11 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode) return err; } -static int do_fchmodat(int dfd, const char __user *filename, umode_t mode) +static int do_fchmodat4(int dfd, const char __user *filename, umode_t mode, int lookup_flags) { struct path path; int error; - unsigned int lookup_flags = LOOKUP_FOLLOW; + retry: error = user_path_at(dfd, filename, lookup_flags, &path); if (!error) { @@ -689,15 +689,25 @@ static int do_fchmodat(int dfd, const char __user *filename, umode_t mode) return error; } +SYSCALL_DEFINE4(fchmodat4, int, dfd, const char __user *, filename, + umode_t, mode, int, flags) +{ + if (unlikely(flags & ~AT_SYMLINK_NOFOLLOW)) + return -EINVAL; + + return do_fchmodat4(dfd, filename, mode, + flags & AT_SYMLINK_NOFOLLOW ? 0 : LOOKUP_FOLLOW); +} + SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode) { - return do_fchmodat(dfd, filename, mode); + return do_fchmodat4(dfd, filename, mode, LOOKUP_FOLLOW); } SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode) { - return do_fchmodat(AT_FDCWD, filename, mode); + return do_fchmodat4(AT_FDCWD, filename, mode, LOOKUP_FOLLOW); } /** diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 497bdd968c32..b17d37d2bad6 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -466,6 +466,8 @@ asmlinkage long sys_chroot(const char __user *filename); asmlinkage long sys_fchmod(unsigned int fd, umode_t mode); asmlinkage long sys_fchmodat(int dfd, const char __user *filename, umode_t mode); +asmlinkage long sys_fchmodat4(int dfd, const char __user *filename, + umode_t mode, int flags); asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group, int flag); asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group);