linux-kernel - [PATCH] scsi_prep_fn() check for empty queue

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Message-Id: <1372237363-5156-1-git-send-email-maxim.uvarov@oracle.com>
Date:	Wed, 26 Jun 2013 13:02:43 +0400
From:	Maxim Uvarov <maxim.uvarov@...cle.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-scsi@...r.kernel.org, JBottomley@...allels.com
Subject: [PATCH] scsi_prep_fn() check for empty queue

This fix:
end_request: I/O error, dev sdc, sector 976576
 rport-0:0-3: blocked FC remote port time out: removing target and saving
binding
BUG: unable to handle kernel NULL pointer dereference at 0000000000000400
IP: [<ffffffff812f0cc2>] scsi_prep_state_check+0xe/0x99
 [<ffffffff812f1f9d>] scsi_setup_blk_pc_cmnd+0x1b/0x115
 [<ffffffff812f20c0>] scsi_prep_fn+0x29/0x3b
 [<ffffffff8121cfb9>] blk_peek_request+0xe1/0x1b3
 [<ffffffff812f1400>] scsi_request_fn+0x3a/0x4d2
 [<ffffffff8121d916>] __generic_unplug_device+0x32/0x36
 [<ffffffff81220f4b>] blk_execute_rq_nowait+0x77/0x9e
 [<ffffffff81221018>] blk_execute_rq+0xa6/0xde
 [<ffffffff8144f24b>] ? printk+0x41/0x46
 [<ffffffffa00a21c5>] ? get_rdac_req+0x81/0xe8 [scsi_dh_rdac]
 [<ffffffffa00a273a>] send_mode_select+0x29f/0x489 [scsi_dh_rdac]
 [<ffffffff810c5d9b>] ? probe_workqueue_execution+0xb1/0xce
 [<ffffffff81071e38>] worker_thread+0x1a9/0x237
 [<ffffffffa00a249b>] ? send_mode_select+0x0/0x489 [scsi_dh_rdac]
 [<ffffffff8107651b>] ? autoremove_wake_function+0x0/0x39
 [<ffffffff81071c8f>] ? worker_thread+0x0/0x237
 [<ffffffff81076222>] kthread+0x7f/0x87
 [<ffffffff81012d2a>] child_rip+0xa/0x20
 [<ffffffff810761a3>] ? kthread+0x0/0x87
 [<ffffffff81012d20>] ? child_rip+0x0/0x20
Signed-off-by: Maxim Uvarov <maxim.uvarov@...cle.com>
---
 drivers/scsi/scsi_lib.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 86d5220..8e89ed9 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1295,6 +1295,9 @@ int scsi_prep_fn(struct request_queue *q, struct request *req)
 	struct scsi_device *sdev = q->queuedata;
 	int ret = BLKPREP_KILL;
 
+	if (!sdev)
+		return ret;
+
 	if (req->cmd_type == REQ_TYPE_BLOCK_PC)
 		ret = scsi_setup_blk_pc_cmnd(sdev, req);
 	return scsi_prep_return(q, req, ret);
-- 
1.7.9.5

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