The patch below does not apply to the 5.11-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 6d042ffb598ed83e7d5623cc961d249def5b9829 Mon Sep 17 00:00:00 2001
From: Palash Oswal hello@oswalpalash.com Date: Tue, 27 Apr 2021 18:21:49 +0530 Subject: [PATCH] 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 863420e184cf..81096f3b01ea 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);