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@xxxxxxxxxxxxxxxxxxxxxxxxx > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Palash Oswal <hello@xxxxxxxxxxxxxxx> > --- > 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; > WARN_ON_ONCE(!sqd || ctx->sq_data->thread != current); > > atomic_inc(&tctx->in_idle); > -- Pavel Begunkov
