linux-kernel - [PATCH 3.16 42/61] scsi: sg: don't return bogus Sg

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Date:   Tue, 09 Jun 2020 19:04:33 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Johannes Thumshirn" <jthumshirn@...e.de>,
        "Andrey Konovalov" <andreyknvl@...gle.com>,
        "Christoph Hellwig" <hch@....de>,
        "Tony Battersby" <tonyb@...ernetics.com>,
        "Hannes Reinecke" <hare@...e.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Doug Gilbert" <dgilbert@...erlog.com>
Subject: [PATCH 3.16 42/61] scsi: sg: don't return bogus Sg_requests

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Thumshirn <jthumshirn@...e.de>

commit 48ae8484e9fc324b4968d33c585e54bc98e44d61 upstream.

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>
Reviewed-by: Hannes Reinecke <hare@...e.de>
Acked-by: Doug Gilbert <dgilbert@...erlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Cc: Tony Battersby <tonyb@...ernetics.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/sg.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2085,11 +2085,12 @@ 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 */