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Date: Tue, 31 Jan 2017 10:50:49 +0100 From: Dmitry Vyukov <dvyukov@...gle.com> To: Johannes Thumshirn <jthumshirn@...e.de> Cc: jejb@...ux.vnet.ibm.com, "Martin K. Petersen" <martin.petersen@...cle.com>, linux-scsi <linux-scsi@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk>, syzkaller <syzkaller@...glegroups.com>, Hannes Reinecke <hare@...e.de> Subject: Re: scsi: BUG in scsi_init_io On Tue, Jan 31, 2017 at 10:20 AM, Johannes Thumshirn <jthumshirn@...e.de> wrote: > On Tue, Jan 31, 2017 at 09:55:52AM +0100, Dmitry Vyukov wrote: >> Hello, >> >> The following program triggers BUG in scsi_init_io: > > Well crashing a machine just because of an empty dma transfer is a bit harsh, > isn't it? > > From 86e6fa5f618fe588b98e923e032f33e075fcd4f4 Mon Sep 17 00:00:00 2001 > From: Johannes Thumshirn <jthumshirn@...e.de> > Date: Tue, 31 Jan 2017 10:16:00 +0100 > Subject: [PATCH] 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. > > Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de> > --- > 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 e9e1e14..414588a 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(!blk_rq_nr_phys_segments(rq))) > + return -EINVAL; Please-please-please, let's not use WARN for something that is not a kernel bug and is user-triggerable. This makes it impossible to automate kernel testing and requires hiring an army of people doing mechanical job of sorting out WARNING reports into kernel-bugs and non-kernel-bugs. If the message is absolutely necessary (while kernel does not generally explain every EINVAL on console), the following will do: if (!blk_rq_nr_phys_segments(rq)) { pr_err("you are doing something wrong\n"); return -EINVAL; } > error = scsi_init_sgtable(rq, &cmd->sdb); > if (error) > -- > 2.10.2 > > > -- > Johannes Thumshirn Storage > jthumshirn@...e.de +49 911 74053 689 > SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg > GF: Felix Imendörffer, Jane Smithard, Graham Norton > HRB 21284 (AG Nürnberg) > Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
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