From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Fri, 16 May 2025 21:50:27 +0000 (+0200)
Subject: tar: Clear safe_fprintf stack before usage
X-Git-Tag: v3.8.0~15^2~4
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=3f1e45d14673f2a85fb051198c01884a1362a106;p=thirdparty%2Flibarchive.git

tar: Clear safe_fprintf stack before usage

The stack buffer is never cleared, which can become an issue depending
on vsnprintf implementation's behavior if -1 is returned. The code
would eventually fall back to stack buffer which might be not
nul terminated.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
---

diff --git a/tar/util.c b/tar/util.c
index 7b9db5ddc..dabb94058 100644
--- a/tar/util.c
+++ b/tar/util.c
@@ -87,6 +87,7 @@ safe_fprintf(FILE * restrict f, const char * restrict fmt, ...)
 	char try_wc;
 
 	/* Use a stack-allocated buffer if we can, for speed and safety. */
+	memset(fmtbuff_stack, '\0', sizeof(fmtbuff_stack));
 	fmtbuff_heap = NULL;
 	fmtbuff_length = sizeof(fmtbuff_stack);
 	fmtbuff = fmtbuff_stack;