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

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commit dc432c3d7f9bceb3de6f5b44fb9c657c9810ed6d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Steven Rostedt (VMware) 2018-05-09 11:59:32 -04:00 committed by Greg Kroah-Hartman
parent 586d02c147
commit 8999971292
1 changed files with 3 additions and 0 deletions
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3
kernel/trace/trace_events_filter.c
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@ -338,6 +338,9 @@ 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;