[PATCH] tools lib traceevent: Fix BOF in arg_eval() when printing large negative values

[PATCH] tools lib traceevent: Fix BOF in arg_eval() when printing large negative values

[Mathias Krause]

The buffer for printing large negative values is one byte too small as
can be seen below when trying to print LONG_MIN:

  $ printf "%lld" $[0x8000000000000000] | wc -c
  20

The number already needs 20 bytes, plus the '\0' terminator makes it 21
bytes. This results in a buffer overflow that gets detected by the
_FORTIFY_SOURCE logic and, in turn, ends up in an abort(3) call.

Resize the buffer to 22 bytes to have yet another spare byte.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
---
This commit should probably be backported to, at least, the
trace-cmd-stable-v2.6 branch as I ran into the issue there by using the
stock Debian/testing version of trace-cmd, trying to do a 'trace-cmd report'
on a large trace file.
---
 lib/traceevent/event-parse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/traceevent/event-parse.c b/lib/traceevent/event-parse.c
index 6f7f4be3c4ea..a8a4366d51cc 100644
--- a/lib/traceevent/event-parse.c
+++ b/lib/traceevent/event-parse.c
@@ -2457,7 +2457,7 @@ static int arg_num_eval(struct tep_print_arg *arg, long long *val)
 static char *arg_eval (struct tep_print_arg *arg)
 {
 	long long val;
-	static char buf[20];
+	static char buf[22];
 
 	switch (arg->type) {
 	case TEP_PRINT_ATOM:
-- 
2.20.1