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

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

[Johannes Thumshirn]

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@suse.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

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

[Laurence Oberman]

----- Original Message -----
> From: "Johannes Thumshirn" <jthumshirn@suse.de>
> To: "Martin K . Petersen" <martin.petersen@oracle.com>, "James Bottomley" <jejb@linux.vnet.ibm.com>
> Cc: "Linux SCSI Mailinglist" <linux-scsi@vger.kernel.org>, "Linux Kernel Mailinglist" <linux-kernel@vger.kernel.org>,
> "Narsimhulu Musini" <nmusini@cisco.com>, "Sesidhar Baddela" <sebaddel@cisco.com>, "Johannes Thumshirn"
> <jthumshirn@suse.de>
> Sent: Thursday, June 23, 2016 8:37:20 AM
> 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@suse.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
> 
> --
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> 

Looks fine to me
Reviewed-by Laurence Oberman <loberman@redhat.com>