On 7/20/2020 5:38 PM, Eric Biggers wrote:
On Wed, Jul 08, 2020 at 01:15:20PM -0700, Eric Biggers wrote:
From: Eric Biggers ebiggers@google.com
smk_write_relabel_self() frees memory from the task's credentials with no locking, which can easily cause a use-after-free because multiple tasks can share the same credentials structure.
Fix this by using prepare_creds() and commit_creds() to correctly modify the task's credentials.
Reproducer for "BUG: KASAN: use-after-free in smk_write_relabel_self":
#include <fcntl.h> #include <pthread.h> #include <unistd.h>
static void *thrproc(void *arg) { int fd = open("/sys/fs/smackfs/relabel-self", O_WRONLY); for (;;) write(fd, "foo", 3); }
int main() { pthread_t t; pthread_create(&t, NULL, thrproc, NULL); thrproc(NULL); }
Reported-by: syzbot+e6416dabb497a650da40@syzkaller.appspotmail.com Fixes: 38416e53936e ("Smack: limited capability for changing process label") Cc: stable@vger.kernel.org # v4.4+ Signed-off-by: Eric Biggers ebiggers@google.com
Ping.
I have queued your patch and will be pushing it for next shortly.