From: Ondrej Zajicek (work) <santiago@crfreenet.org>
Date: Mon, 12 Apr 2021 15:01:31 +0000 (+0200)
Subject: Lib: Fix handling of buffers in timestamp formatting
X-Git-Tag: v2.0.9~85
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9c41e1ca3e93d4498eaa085139caf1545e08c1d8;p=thirdparty%2Fbird.git

Lib: Fix handling of buffers in timestamp formatting

The code in tm_format_real_time() mixed up two buffers and their
sizes, which may cause crash in MRT dumping code.

Thanks to Piotr Wydrych for the bugreport.
---

diff --git a/lib/timer.c b/lib/timer.c
index a5abbcc46..381163d0b 100644
--- a/lib/timer.c
+++ b/lib/timer.c
@@ -365,8 +365,9 @@ tm_format_real_time(char *x, size_t max, const char *fmt, btime t)
   if (!localtime_r(&ts, &tm))
     return 0;
 
-  byte tbuf[TM_DATETIME_BUFFER_SIZE];
-  if (!strfusec(tbuf, max, fmt, t2))
+  size_t tbuf_size = MIN(max, 4096);
+  byte *tbuf = alloca(tbuf_size);
+  if (!strfusec(tbuf, tbuf_size, fmt, t2))
     return 0;
 
   if (!strftime(x, max, tbuf, &tm))