From: Johannes Thumshirn Date: Tue, 31 Jan 2017 09:16:00 +0000 (+0100) Subject: scsi: don't BUG_ON() empty DMA transfers X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=fd3fc0b4d7305fa7246622dcc0dec69c42443f45;p=openwrt%2Fstaging%2Fblogic.git scsi: don't BUG_ON() empty DMA transfers Don't crash the machine just because of an empty transfer. Use WARN_ON() combined with returning an error. Found by Dmitry Vyukov and syzkaller. [ Changed to "WARN_ON_ONCE()". Al has a patch that should fix the root cause, but a BUG_ON() is not acceptable in any case, and a WARN_ON() might still be a cause of excessive log spamming. NOTE! If this warning ever triggers, we may end up leaking resources, since this doesn't bother to try to clean the command up. So this WARN_ON_ONCE() triggering does imply real problems. But BUG_ON() is much worse. People really need to stop using BUG_ON() for "this shouldn't ever happen". It makes pretty much any bug worse. - Linus ] Signed-off-by: Johannes Thumshirn Reported-by: Dmitry Vyukov Cc: James Bottomley Cc: Al Viro Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index e9e1e141af9c..78db07fd8055 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1040,7 +1040,8 @@ int scsi_init_io(struct scsi_cmnd *cmd) bool is_mq = (rq->mq_ctx != NULL); int error; - BUG_ON(!blk_rq_nr_phys_segments(rq)); + if (WARN_ON_ONCE(!blk_rq_nr_phys_segments(rq))) + return -EINVAL; error = scsi_init_sgtable(rq, &cmd->sdb); if (error)