io_uring: io_wq_create() returns an error pointer, not NULL

syzbot reported an issue where we crash at setup time if failslab is
used. The issue is that io_wq_create() returns an error pointer on
failure, not NULL. Hence io_uring thought the io-wq was setup just
fine, but in reality it's a garbage error pointer.

Use IS_ERR() instead of a NULL check, and assign ret appropriately.

Reported-by: syzbot+221cc24572a2fed23b6b@syzkaller.appspotmail.com
Fixes: 561fb04a6a ("io_uring: replace workqueue usage with io-wq")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2019-10-30 08:42:56 -06:00
parent 842f96124c
commit 975c99a570

View File

@ -3489,8 +3489,9 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
/* Do QD, or 4 * CPUS, whatever is smallest */
concurrency = min(ctx->sq_entries, 4 * num_online_cpus());
ctx->io_wq = io_wq_create(concurrency, ctx->sqo_mm);
if (!ctx->io_wq) {
ret = -ENOMEM;
if (IS_ERR(ctx->io_wq)) {
ret = PTR_ERR(ctx->io_wq);
ctx->io_wq = NULL;
goto err;
}