On 4/27/21 1:51 PM, Palash Oswal wrote:
syzkaller identified KASAN: null-ptr-deref Write in io_uring_cancel_sqpoll on v5.12
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.
Looks good to me, but better to add a comment why it can be ignored, e.g. "can skip it as it couldn't have submitted requests without tctx"
Also a nit: s/current->io_uring/tctx/
Reported-by: syzbot+be51ca5a4d97f017cd50@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Palash Oswal hello@oswalpalash.com
fs/io_uring.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c index dff34975d86b..eccad51b7954 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -8998,6 +8998,8 @@ static void io_uring_cancel_sqpoll(struct io_ring_ctx *ctx) s64 inflight; DEFINE_WAIT(wait);
- if (!current->io_uring)
return;atomic_inc(&tctx->in_idle);