Commit bc78abbd authored Sep 25, 2018 by Kirill Tkhai Committed by Miklos Szeredi Sep 28, 2018

fuse: Fix use-after-free in fuse_dev_do_read()



We may pick freed req in this way:

[cpu0]                                  [cpu1]
fuse_dev_do_read()                      fuse_dev_do_write()
   list_move_tail(&req->list, ...);     ...
   spin_unlock(&fpq->lock);             ...
   ...                                  request_end(fc, req);
   ...                                    fuse_put_request(fc, req);
   if (test_bit(FR_INTERRUPTED, ...))
         queue_interrupt(fiq, req);

Fix that by keeping req alive until we finish all manipulations.

Reported-by:  <syzbot+4e975615ca01f2277bdd@syzkaller.appspotmail.com>
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 46c34a34 ("fuse: no fc->lock for pqueue parts")
Cc: <stable@vger.kernel.org> # v4.2

parent 6bf4ca7f

fs/fuse/dev.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -1311,12 +1311,14 @@ static ssize_t fuse_dev_do_read(struct fuse_dev fud, struct file file,
		goto out_end;
		}
		list_move_tail(&req->list, &fpq->processing);
		__fuse_get_request(req);
		spin_unlock(&fpq->lock);
		set_bit(FR_SENT, &req->flags);
		/* matches barrier in request_wait_answer() */
		smp_mb__after_atomic();
		if (test_bit(FR_INTERRUPTED, &req->flags))
		queue_interrupt(fiq, req);
		fuse_put_request(fc, req);

		return reqsize;

Admin message