Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Sat, 01 Apr 2017 14:17:50 +0100 | Subject | [PATCH 3.16 18/19] aio: mark AIO pseudo-fs noexec |
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3.16.43-rc1 review patch. If anyone has any objections, please let me know.
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From: Jann Horn <jann@thejh.net>
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> [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@decadent.org.uk> --- 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))
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