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@xxxxxxxxxxxxxxx>
Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
---
drivers/hwtracing/stm/core.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 736862967e32..7e2bfb257d6b 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -558,7 +558,7 @@ 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;
- int ret = -EINVAL;
+ int ret = -EINVAL, wlimit = 1;
u32 size;
if (stmf->output.nr_chans)
@@ -586,8 +586,10 @@ 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;
ret = stm_file_assign(stmf, id->id, id->width);
--
2.20.1
