linux-kernel - Re: [PATCH] stm class: Fix out of bound access from bitmap allocation

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Message-ID: <87mukqc7v8.fsf@ashishki-desk.ger.corp.intel.com>
Date:   Tue, 16 Apr 2019 18:00:59 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mulu He <muluhe@...eaurora.org>,
        Tingwei Zhang <tingwei@...eaurora.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        linux-stm32@...md-mailman.stormreply.com,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>
Cc:     Rajendra Nayak <rnayak@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        stable@...r.kernel.org, alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH] stm class: Fix out of bound access from bitmap allocation

Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org> writes:

> From: Mulu He <muluhe@...eaurora.org>
>
> Bitmap allocation works on array of unsigned longs and
> for stm master allocation when the number of software
> channels is 32, 4 bytes are allocated and there is a out of
> bound access at the first 8 bytes access of bitmap region.

Does the below fix the problem for you?

>From fb22b9ab109b332e58d72df13563e270befbd0e3 Mon Sep 17 00:00:00 2001
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Date: Tue, 16 Apr 2019 17:47:02 +0300
Subject: [PATCH] stm class: Fix channel bitmap on 32-bit systems

Commit 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace
Module devices") naively calculates the channel bitmap size in 64-bit
chunks regardless of the size of underlying unsigned long, making the
bitmap half as big on a 32-bit system. This leads to an out of bounds
access with the upper half of the bitmap.

Fix this by using BITS_TO_LONGS. While at it, convert to using
struct_size() for the total size calculation of the master struct.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
Reported-by: Mulu He <muluhe@...eaurora.org>
Cc: stable@...r.kernel.org # v4.4+
---
 drivers/hwtracing/stm/core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 5b5807cbcf7c..8c45e79e47db 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -166,11 +166,9 @@ stm_master(struct stm_device *stm, unsigned int idx)
 static int stp_master_alloc(struct stm_device *stm, unsigned int idx)
 {
 	struct stp_master *master;
-	size_t size;
 
-	size = ALIGN(stm->data->sw_nchannels, 8) / 8;
-	size += sizeof(struct stp_master);
-	master = kzalloc(size, GFP_ATOMIC);
+	master = kzalloc(struct_size(master, chan_map, BITS_TO_LONGS(stm->data->sw_nchannels)),
+			 GFP_ATOMIC);
 	if (!master)
 		return -ENOMEM;
 
-- 
2.20.1