From: Frank Ch. Eigler <fche@redhat.com>
Date: Thu, 13 Jan 2022 23:33:15 +0000 (-0500)
Subject: PR28778: gcc warning tweak for sprintf precision parameter
X-Git-Tag: release-4.7~84
X-Git-Url: https://sourceware.org/git/?a=commitdiff_plain;h=b0422e9e5a539164af75cddcaeb01bceca56bf12;p=systemtap.git

PR28778: gcc warning tweak for sprintf precision parameter

A precision=-1 sentinel value got interpreted as UINT_MAX in a
context, leading to diagnostics like:

/usr/share/systemtap/runtime/vsprintf.c:341:23: error: 'strnlen' specified bound 4294967295 may exceed maximum object size 2147483647 [-Werror=stringop-overread]

Adding a clamp_t() around the parameter field to keep it limited to
STP_BUFFER_SIZE (8K by default), which is apprx. the limit for a
single printf.
---

diff --git a/runtime/vsprintf.c b/runtime/vsprintf.c
index cd31a938b..606f685e8 100644
--- a/runtime/vsprintf.c
+++ b/runtime/vsprintf.c
@@ -338,7 +338,7 @@ _stp_vsprint_memory(char * str, char * end, const char * ptr,
 	if (format == 's') {
 		if ((unsigned long)ptr < PAGE_SIZE)
 			ptr = "<NULL>";
-		len = strnlen(ptr, precision);
+		len = strnlen(ptr, clamp_t(size_t, precision, 0, STP_BUFFER_SIZE));                
 	}
 	else if (precision > 0)
 		len = precision;
@@ -410,7 +410,7 @@ _stp_vsprint_memory_size(const char * ptr, int width, int precision,
 	if (format == 's') {
 		if ((unsigned long)ptr < PAGE_SIZE)
 			ptr = "<NULL>";
-		len = strnlen(ptr, precision);
+		len = strnlen(ptr, clamp_t(size_t, precision, 0, STP_BUFFER_SIZE));
 	}
 	else if (precision > 0)
 		len = precision;