On Mon, Jul 13, 2020 at 11:18:36AM +0100, Christoph Hellwig wrote: > On Fri, Jul 10, 2020 at 10:34:19PM -0700, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > This is not a crash, but a WARN_ONCE. A pre-existing one that just > slightly changed the printed message recently. > It doesn't really matter. WARN is for indicating kernel bugs only. A user-triggable WARN is a bug. Either the bug that makes the WARN reachable needs to be fixed, or if the WARN is legitimately user-reachable it needs to be removed or replaced with a proper ratelimited log message. This one looks legitimately user-reachable, so we could do: diff --git a/block/blk-core.c b/block/blk-core.c index d9d632639bd1..354c51ad5c81 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -854,8 +854,8 @@ static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part) if (op_is_flush(bio->bi_opf) && !bio_sectors(bio)) return false; - WARN_ONCE(1, - "Trying to write to read-only block-device %s (partno %d)\n", + pr_warn_ratelimited( + "block: trying to write to read-only block-device %s (partno %d)\n", bio_devname(bio, b), part->partno); /* Older lvm-tools actually trigger this */ return false; We could also show current->comm and current->pid if they would be useful here. And yes, this is preexisting which is why syzbot has reported this before (https://syzkaller.appspot.com/bug?id=79eda145ab047a0dc7d03ca5fcb1cf12206eb481). Just no one has bothered to fix it yet. - Eric
