Linus,

Working on some new updates to trace filtering, I noticed that the regex_match_front() test was updated to be limited to the size of the pattern instead of the full test string. But as the test string is not guaranteed to be nul terminated, it still needs to consider the size of the test string.

Please pull the latest trace-v4.17-rc4 tree, which can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git trace-v4.17-rc4

Tag SHA1: cb82e07247fa5f1a91940a2928fb260256727a14 Head SHA1: dc432c3d7f9bceb3de6f5b44fb9c657c9810ed6d

Steven Rostedt (VMware) (1): tracing: Fix regex_match_front() to not over compare the test string

---- kernel/trace/trace_events_filter.c | 3 +++ 1 file changed, 3 insertions(+) --------------------------- commit dc432c3d7f9bceb3de6f5b44fb9c657c9810ed6d Author: Steven Rostedt (VMware) rostedt@goodmis.org Date: Wed May 9 11:59:32 2018 -0400

tracing: Fix regex_match_front() to not over compare the test string

The regex match function regex_match_front() in the tracing filter logic, was fixed to test just the pattern length from testing the entire test string. That is, it went from strncmp(str, r->pattern, len) to strcmp(str, r->pattern, r->len).

The issue is that str is not guaranteed to be nul terminated, and if r->len is greater than the length of str, it can access more memory than is allocated.

The solution is to add a simple test if (len < r->len) return 0.

Cc: stable@vger.kernel.org Fixes: 285caad415f45 ("tracing/filters: Fix MATCH_FRONT_ONLY filter matching") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 1f951b3df60c..7d306b74230f 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -762,6 +762,9 @@ static int regex_match_full(char *str, struct regex *r, int len)

static int regex_match_front(char *str, struct regex *r, int len) { + if (len < r->len) + return 0; + if (strncmp(str, r->pattern, r->len) == 0) return 1; return 0;