3.16.43-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Jann Horn <jann@xxxxxxxxx>
commit 22f6b4d34fcf039c63a94e7670e0da24f8575a5a upstream.
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@xxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.16: we don't have super_block::s_iflags; use
file_system_type::fs_flags instead]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
fs/aio.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -226,6 +226,7 @@ static int __init aio_setup(void)
.name = "aio",
.mount = aio_mount,
.kill_sb = kill_anon_super,
+ .fs_flags = FS_NOEXEC,
};
aio_mnt = kern_mount(&aio_fs);
if (IS_ERR(aio_mnt))