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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     stern@rowland.harvard.edu, gregkh@linuxfoundation.org
Cc:     linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net,
        linux-kernel@vger.kernel.org, Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH v2] usb: storage: sddr55: Fix a possible null-pointer dereference in sddr55_transport()
Date:   Mon, 29 Jul 2019 19:49:36 +0800
Message-Id: <20190729114936.6103-1-baijiaju1990@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In sddr55_transport(), there is an if statement on line 836 to check
whether info->lba_to_pba is NULL:
    if (info->lba_to_pba == NULL || ...)

When info->lba_to_pba is NULL, it is used on line 948:
    pba = info->lba_to_pba[lba];

Thus, a possible null-pointer dereference may occur.

To fix this bug, info->lba_to_pba is checked before being used.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
v2:
* Avoid uninitialized access of pba.
  Thank Oliver for helpful advice.

---
 drivers/usb/storage/sddr55.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/storage/sddr55.c b/drivers/usb/storage/sddr55.c
index b8527c55335b..d23aff16091e 100644
--- a/drivers/usb/storage/sddr55.c
+++ b/drivers/usb/storage/sddr55.c
@@ -945,7 +945,7 @@ static int sddr55_transport(struct scsi_cmnd *srb, struct us_data *us)
 			return USB_STOR_TRANSPORT_FAILED;
 		}
 
-		pba = info->lba_to_pba[lba];
+		pba = info->lba_to_pba ? info->lba_to_pba[lba] : 0;
 
 		if (srb->cmnd[0] == WRITE_10) {
 			usb_stor_dbg(us, "WRITE_10: write block %04X (LBA %04X) page %01X pages %d\n",
-- 
2.17.0