linux-kernel - [PATCH] snic: Fix use-after-free in case of a dma mapping error

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Date:	Thu, 23 Jun 2016 14:37:20 +0200
From:	Johannes Thumshirn <jthumshirn@...e.de>
To:	"Martin K . Petersen" <martin.petersen@...cle.com>,
	James Bottomley <jejb@...ux.vnet.ibm.com>
Cc:	Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
	Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Narsimhulu Musini <nmusini@...co.com>,
	Sesidhar Baddela <sebaddel@...co.com>,
	Johannes Thumshirn <jthumshirn@...e.de>
Subject: [PATCH] snic: Fix use-after-free in case of a dma mapping error

If there is a dma mapping error snic kfree()s buf right before printing it.
Change the order to not accidently trip on memory that's not owned by us
anymore.

Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
---
 drivers/scsi/snic/snic_disc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/snic/snic_disc.c b/drivers/scsi/snic/snic_disc.c
index b0fefd6..b106596 100644
--- a/drivers/scsi/snic/snic_disc.c
+++ b/drivers/scsi/snic/snic_disc.c
@@ -113,11 +113,11 @@ snic_queue_report_tgt_req(struct snic *snic)
 
 	pa = pci_map_single(snic->pdev, buf, buf_len, PCI_DMA_FROMDEVICE);
 	if (pci_dma_mapping_error(snic->pdev, pa)) {
-		kfree(buf);
-		snic_req_free(snic, rqi);
 		SNIC_HOST_ERR(snic->shost,
 			      "Rpt-tgt rspbuf %p: PCI DMA Mapping Failed\n",
 			      buf);
+		kfree(buf);
+		snic_req_free(snic, rqi);
 		ret = -EINVAL;
 
 		goto error;
-- 
2.8.4