[patch] perf tool buffer overflow in perf_header__read_build_ids

[Vince Weaver]

Hello

my perf_tool_fuzzer has found another issue, this one a buffer overflow
in perf_header__read_build_ids.  The build id filename is read in with a 
filename length read from the perf.data file, but this can be longer than
PATH_MAX which will smash the stack.

This might not be the right fix, not sure if filename should be NUL
terminated or not.

Signed-off-by: Vince Weaver <vincent.weaver@xxxxxxxxx>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index c24db7f4909c..9a893a26e678 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2001,6 +2001,9 @@ static int perf_header__read_build_ids(struct perf_header *header,
 			perf_event_header__bswap(&bev.header);
 
 		len = bev.header.size - sizeof(bev);
+
+		if (len>PATH_MAX) len=PATH_MAX;
+
 		if (readn(input, filename, len) != len)
 			goto out;
 		/*