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stm class: Prevent division by zero

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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: 7bd1d4093c ("stm class: Introduce an abstraction for System Trace Module devices")
CC: stable@vger.kernel.org # v4.4+
This commit is contained in:
Alexander Shishkin 2019-02-21 14:19:17 +02:00
parent a1d75dad3a
commit bf7cbaae08
1 changed files with 5 additions and 3 deletions
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8
drivers/hwtracing/stm/core.c
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@ -735,7 +735,7 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
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)
@ -763,8 +763,10 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
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;