[PATCH 4.4 04/15] scsi: dont BUG_ON() empty DMA transfers
From: Greg Kroah-Hartman
Date: Tue Feb 21 2017 - 08:11:07 EST
4.4-stable review patch. If anyone has any objections, please let me know.
From: Johannes Thumshirn <jthumshirn@xxxxxxx>
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
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 <jthumshirn@xxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: James Bottomley <jejb@xxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/scsi/scsi_lib.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
@@ -1120,7 +1120,8 @@ int scsi_init_io(struct scsi_cmnd *cmd)
bool is_mq = (rq->mq_ctx != NULL);
+ if (WARN_ON_ONCE(!rq->nr_phys_segments))
+ return -EINVAL;
error = scsi_init_sgtable(rq, &cmd->sdb);