@@ -8,6 +8,7 @@
#define MFD_CLOEXEC 0x0001U
#define MFD_ALLOW_SEALING 0x0002U
#define MFD_HUGETLB 0x0004U
+#define MFD_INACCESSIBLE 0x0008U
/*
* Huge page size encoding when MFD_HUGETLB is specified, and a huge page
@@ -245,7 +245,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
-#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB)
+#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \
+ MFD_INACCESSIBLE)
SYSCALL_DEFINE2(memfd_create,
const char __user *, uname,
@@ -267,6 +268,10 @@ SYSCALL_DEFINE2(memfd_create,
return -EINVAL;
}
+ /* Disallow sealing when MFD_INACCESSIBLE is set. */
+ if (flags & MFD_INACCESSIBLE && flags & MFD_ALLOW_SEALING)
+ return -EINVAL;
+
/* length includes terminating zero */
len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
if (len <= 0)
@@ -315,6 +320,11 @@ SYSCALL_DEFINE2(memfd_create,
*file_seals &= ~F_SEAL_SEAL;
}
+ if (flags & MFD_INACCESSIBLE) {
+ file_seals = memfd_file_seals_ptr(file);
+ *file_seals &= F_SEAL_SEAL | F_SEAL_INACCESSIBLE;
+ }
+
fd_install(fd, file);
kfree(name);
return fd;
Introduce a new memfd_create() flag indicating the content of the created memfd is inaccessible from userspace. It does this by force setting F_SEAL_INACCESSIBLE seal when the file is created. It also set F_SEAL_SEAL to prevent future sealing, which means, it can not coexist with MFD_ALLOW_SEALING. Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com> --- include/uapi/linux/memfd.h | 1 + mm/memfd.c | 12 +++++++++++- 2 files changed, 12 insertions(+), 1 deletion(-)