From 22f6b4d34fcf039c63a94e7670e0da24f8575a5a Mon Sep 17 00:00:00 2001
From: Jann Horn <jann@thejh.net>
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 <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>
---
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
--
2.51.0