io_uring: Check current->io_uring in io_uring_cancel_sqpoll
syzkaller identified KASAN: null-ptr-deref Write in
io_uring_cancel_sqpoll.
io_uring_cancel_sqpoll is called by io_sq_thread before calling
io_uring_alloc_task_context. This leads to current->io_uring being NULL.
io_uring_cancel_sqpoll should not have to deal with threads where
current->io_uring is NULL.
In order to cast a wider safety net, perform input sanitisation directly
in io_uring_cancel_sqpoll and return for NULL value of current->io_uring.
This is safe since if current->io_uring isn't set, then there's no way
for the task to have submitted any requests.
Reported-by: syzbot+be51ca5a4d97f017cd50@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Palash Oswal <hello@oswalpalash.com>
Link: https://lore.kernel.org/r/20210427125148.21816-1-hello@oswalpalash.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 863420e..81096f3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9044,6 +9044,8 @@ static void io_uring_cancel_sqpoll(struct io_sq_data *sqd)
s64 inflight;
DEFINE_WAIT(wait);
+ if (!current->io_uring)
+ return;
WARN_ON_ONCE(!sqd || sqd->thread != current);
atomic_inc(&tctx->in_idle);
