From 22f6b4d34fcf039c63a94e7670e0da24f8575a5a Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 16 Sep 2016 00:31:22 +0200 Subject: [PATCH] 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 #include #include #include #include #include #include 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 Signed-off-by: Linus Torvalds --- fs/aio.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) 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, + AIO_RING_MAGIC); + + if (!IS_ERR(root)) + root->d_sb->s_iflags |= SB_I_NOEXEC; + return root; } /* aio_setup -- 2.20.1