[PATCH] stm class: Fix out of bound access from bitmap allocation

[Sai Prakash Ranjan]

From: Mulu He <muluhe@xxxxxxxxxxxxxx>

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.

Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
Signed-off-by: Mulu He <muluhe@xxxxxxxxxxxxxx>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/hwtracing/stm/core.c | 2 +-
 drivers/hwtracing/stm/stm.h  | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 93ce3aa740a9..21a5838f6e67 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -168,7 +168,7 @@ 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 = ALIGN(stm->data->sw_nchannels, STM_MASTER_SZ) / STM_MASTER_SZ;
 	size += sizeof(struct stp_master);
 	master = kzalloc(size, GFP_ATOMIC);
 	if (!master)
diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h
index 3569439d53bb..10eac550c75f 100644
--- a/drivers/hwtracing/stm/stm.h
+++ b/drivers/hwtracing/stm/stm.h
@@ -12,6 +12,8 @@
 
 #include <linux/configfs.h>
 
+#define STM_MASTER_SZ sizeof(unsigned long)
+
 struct stp_policy;
 struct stp_policy_node;
 struct stm_protocol_driver;
-- 
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