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@linux.intel.com>
Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
Reported-by: Mulu He <muluhe@codeaurora.org>
Cc: stable@vger.kernel.org # v4.4+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 5b5807cbcf7cf052ad6cc5d8817ee6f7adb03b28..e55b902560dee28f854718b72f40ca48803de249 100644 (file)
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -166,11 +166,10 @@ 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;