linux-kernel - [PATCH v2] scsi: sg: don't return bogus Sg

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Message-Id: <20170510075340.12125-1-jthumshirn@suse.de>
Date:   Wed, 10 May 2017 09:53:40 +0200
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     "Martin K . Petersen" <martin.petersen@...cle.com>
Cc:     James Bottomley <jejb@...ux.vnet.ibm.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Hannes Reinecke <hare@...e.de>, Christoph Hellwig <hch@....de>,
        Doug Gilbert <dgilbert@...erlog.com>
Subject: [PATCH v2] scsi: sg: don't return bogus Sg_requests

If the list search in sg_get_rq_mark() fails to find a valid request, we
return a bogus element. This then can later lead to a GPF in sg_remove_scat().

So don't return bogus Sg_requests in sg_get_rq_mark() but NULL in case the
list search doesn't find a valid request.

Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Hannes Reinecke <hare@...e.de>
Cc: Christoph Hellwig <hch@....de>
Cc: Doug Gilbert <dgilbert@...erlog.com>
---
Changes to v1:
* Directly return found element within the loop (Hannes)

 drivers/scsi/sg.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0a38ba01b7b4..82c33a6edbea 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2074,11 +2074,12 @@ sg_get_rq_mark(Sg_fd * sfp, int pack_id)
 		if ((1 == resp->done) && (!resp->sg_io_owned) &&
 		    ((-1 == pack_id) || (resp->header.pack_id == pack_id))) {
 			resp->done = 2;	/* guard against other readers */
-			break;
+			write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
+			return resp;
 		}
 	}
 	write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
-	return resp;
+	return NULL;
 }
 
 /* always adds to end of list */
-- 
2.12.0