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Subject[PATCH 5.0 010/238] stm class: Prevent division by zero
Date
5.0-stable review patch.  If anyone has any objections, please let me know.

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

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

commit bf7cbaae0831252b416f375ca9b1027ecd4642dd upstream.

Using STP_POLICY_ID_SET ioctl command with dummy_stm device, or any STM
device that supplies zero mmio channel size, will trigger a division by
zero bug in the kernel.

Prevent this by disallowing channel widths other than 1 for such devices.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
CC: stable@vger.kernel.org # v4.4+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/hwtracing/stm/core.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -732,7 +732,7 @@ static int stm_char_policy_set_ioctl(str
struct stm_device *stm = stmf->stm;
struct stp_policy_id *id;
char *ids[] = { NULL, NULL };
- int ret = -EINVAL;
+ int ret = -EINVAL, wlimit = 1;
u32 size;

if (stmf->output.nr_chans)
@@ -760,8 +760,10 @@ static int stm_char_policy_set_ioctl(str
if (id->__reserved_0 || id->__reserved_1)
goto err_free;

- if (id->width < 1 ||
- id->width > PAGE_SIZE / stm->data->sw_mmiosz)
+ if (stm->data->sw_mmiosz)
+ wlimit = PAGE_SIZE / stm->data->sw_mmiosz;
+
+ if (id->width < 1 || id->width > wlimit)
goto err_free;

ids[0] = id->id;

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