linux-kernel - [PATCH 5.0 030/139] stm class: Fix channel bitmap on 32-bit systems

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Date:   Thu, 23 May 2019 21:05:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mulu He <muluhe@...eaurora.org>
Subject: [PATCH 5.0 030/139] stm class: Fix channel bitmap on 32-bit systems

From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>

commit 51e0f227812ed81a368de54157ebe14396b4be03 upstream.

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+
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/hwtracing/stm/core.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -166,11 +166,10 @@ stm_master(struct stm_device *stm, unsig
 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;