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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@thejh.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
0d9529e1b8