4.20-stable review patch. If anyone has any objections, please let me know.
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From: Alexander Shishkin alexander.shishkin@linux.intel.com
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 alexander.shishkin@linux.intel.com Fixes: ba82664c134ef ("intel_th: Add Memory Storage Unit driver") Cc: stable@vger.kernel.org # v4.4+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/hwtracing/intel_th/msu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/hwtracing/intel_th/msu.c +++ b/drivers/hwtracing/intel_th/msu.c @@ -1423,7 +1423,8 @@ nr_pages_store(struct device *dev, struc if (!end) break;
- len -= end - p; + /* consume the number and the following comma, hence +1 */ + len -= end - p + 1; p = end + 1; } while (len);