The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bf7cbaae0831252b416f375ca9b1027ecd4642dd Mon Sep 17 00:00:00 2001

From: Alexander Shishkin alexander.shishkin@linux.intel.com Date: Thu, 21 Feb 2019 14:19:17 +0200 Subject: [PATCH] stm class: Prevent division by zero

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+

diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index c80b064224f6..c7ba8acfd4d5 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -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;