From c243c6149a5c64efe60fb032f6ffdba8c408211f Mon Sep 17 00:00:00 2001 From: Johannes Thumshirn Date: Tue, 31 Jan 2017 10:16:00 +0100 Subject: [PATCH] scsi: don't BUG_ON() empty DMA transfers commit fd3fc0b4d7305fa7246622dcc0dec69c42443f45 upstream. 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 Signed-off-by: Linus Torvalds Signed-off-by: Willy Tarreau --- drivers/scsi/scsi_lib.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 26e1afec56405..dc1c2f4520f2e 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1011,7 +1011,8 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask) struct request *rq = cmd->request; int error; - BUG_ON(!rq->nr_phys_segments); + if (WARN_ON_ONCE(!rq->nr_phys_segments)) + return -EINVAL; error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask); if (error) -- 2.47.2