diff options
authorJann Horn <jann@thejh.net>2016-09-16 00:31:22 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-15 15:49:28 -0700
commit22f6b4d34fcf039c63a94e7670e0da24f8575a5a (patch)
parent024c7e3756d8a42fc41fe8a9488488b9b09d1dcc (diff)
aio: mark AIO pseudo-fs noexec
This ensures that do_mmap() won't implicitly make AIO memory mappings executable if the READ_IMPLIES_EXEC personality flag is set. Such behavior is problematic because the security_mmap_file LSM hook doesn't catch this case, potentially permitting an attacker to bypass a W^X policy enforced by SELinux. I have tested the patch on my machine. To test the behavior, compile and run this: #define _GNU_SOURCE #include <unistd.h> #include <sys/personality.h> #include <linux/aio_abi.h> #include <err.h> #include <stdlib.h> #include <stdio.h> #include <sys/syscall.h> int main(void) { personality(READ_IMPLIES_EXEC); aio_context_t ctx = 0; if (syscall(__NR_io_setup, 1, &ctx)) err(1, "io_setup"); char cmd[1000]; sprintf(cmd, "cat /proc/%d/maps | grep -F '/[aio]'", (int)getpid()); system(cmd); return 0; } In the output, "rw-s" is good, "rwxs" is bad. Signed-off-by: Jann Horn <jann@thejh.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/aio.c b/fs/aio.c
index fb8e45b88cd4..4fe81d1c60f9 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -239,7 +239,12 @@ static struct dentry *aio_mount(struct file_system_type *fs_type,
static const struct dentry_operations ops = {
.d_dname = simple_dname,
- return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
+ struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, &ops,
+ if (!IS_ERR(root))
+ root->d_sb->s_iflags |= SB_I_NOEXEC;
+ return root;
/* aio_setup