From 8fcfb8fc0f7cabdeca8e1c6cb2773e1dc2e66039 Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Wed, 19 Dec 2018 17:19:22 +0200 Subject: [PATCH] intel_th: msu: Fix an off-by-one in attribute store commit ec5b5ad6e272d8d6b92d1007f79574919862a2d2 upstream. The 'nr_pages' attribute of the 'msc' subdevices parses a comma-separated list of window sizes, passed from userspace. However, there is a bug in the string parsing logic wherein it doesn't exclude the comma character from the range of characters as it consumes them. This leads to an out-of-bounds access given a sufficiently long list. For example: > # echo 8,8,8,8 > /sys/bus/intel_th/devices/0-msc0/nr_pages > ================================================================== > BUG: KASAN: slab-out-of-bounds in memchr+0x1e/0x40 > Read of size 1 at addr ffff8803ffcebcd1 by task sh/825 > > CPU: 3 PID: 825 Comm: npktest.sh Tainted: G W 4.20.0-rc1+ > Call Trace: > dump_stack+0x7c/0xc0 > print_address_description+0x6c/0x23c > ? memchr+0x1e/0x40 > kasan_report.cold.5+0x241/0x308 > memchr+0x1e/0x40 > nr_pages_store+0x203/0xd00 [intel_th_msu] Fix this by accounting for the comma character. Signed-off-by: Alexander Shishkin Fixes: ba82664c134ef ("intel_th: Add Memory Storage Unit driver") Cc: stable@vger.kernel.org # v4.4+ Signed-off-by: Greg Kroah-Hartman --- drivers/hwtracing/intel_th/msu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c index e8d55a153a65..f91d9faf14ea 100644 --- a/drivers/hwtracing/intel_th/msu.c +++ b/drivers/hwtracing/intel_th/msu.c @@ -1429,7 +1429,8 @@ nr_pages_store(struct device *dev, struct device_attribute *attr, if (!end) break; - len -= end - p; + /* consume the number and the following comma, hence +1 */ + len -= end - p + 1; p = end + 1; } while (len); -- 2.20.1