linux-kernel - [PATCH 3.16 150/410] staging: rts5208: Fix "seg_no" calculation in reset_ms

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Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Dan Carpenter" <dan.carpenter@...cle.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 150/410] staging: rts5208: Fix "seg_no" calculation
 in reset_ms_card()

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

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

From: Dan Carpenter <dan.carpenter@...cle.com>

commit 7f7aeea7cf30368b9fdb86dcc9d2c8a3ebc65dfb upstream.

I get some static checker warnings like this:

    drivers/staging/rts5208/ms.c:2607 ms_build_l2p_tbl()
    error: buffer underflow 'ms_card->segment' (-1)-16

The problem is that we memset "ms_card" to zero at the start of the
reset_ms_card() function.  That means that when we try to calculate
"ms_card->total_block / 512 - 1" then it's just always -1.  The fix is
to calculate "seg_no" before doing the memset().

This is a static checker fix, and I am not able to test it.  My theory
is that reset_ms_card() gets very little testing which is why this bug
exists.

Fixes: fa590c222fba ("staging: rts5208: add support for rts5208 and rts5288")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/staging/rts5208/ms.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/staging/rts5208/ms.c
+++ b/drivers/staging/rts5208/ms.c
@@ -2397,6 +2397,7 @@ BUILD_FAIL:
 int reset_ms_card(struct rtsx_chip *chip)
 {
 	struct ms_info *ms_card = &(chip->ms_card);
+	int seg_no = ms_card->total_block / 512 - 1;
 	int retval;
 
 	memset(ms_card, 0, sizeof(struct ms_info));
@@ -2430,7 +2431,7 @@ int reset_ms_card(struct rtsx_chip *chip
 		/* Build table for the last segment,
 		 * to check if L2P table block exists, erasing it
 		 */
-		retval = ms_build_l2p_tbl(chip, ms_card->total_block / 512 - 1);
+		retval = ms_build_l2p_tbl(chip, seg_no);
 		if (retval != STATUS_SUCCESS)
 			TRACE_RET(chip, STATUS_FAIL);
 	}