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Message-ID: <20260805075755.3521503-1-matthias.goergens@gmail.com>
Date: Wed, 5 Aug 2026 15:57:55 +0800
From: Matthias Goergens <matthias.goergens@...il.com>
To: musl@...ts.openwall.com
Cc: Matthias Goergens <matthias.goergens@...il.com>
Subject: [PATCH] fix undefined pointer arithmetic in wcsrchr
On an unsuccessful search, the backwards loop decrements the pointer
past the beginning of the string and then compares that invalid pointer
with the string pointer.
Check for the beginning of the string before decrementing instead. This
preserves the existing results without forming a pointer outside the
array.
---
src/string/wcsrchr.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/src/string/wcsrchr.c b/src/string/wcsrchr.c
index 8961b9e2..aef344b4 100644
--- a/src/string/wcsrchr.c
+++ b/src/string/wcsrchr.c
@@ -3,6 +3,10 @@
wchar_t *wcsrchr(const wchar_t *s, wchar_t c)
{
const wchar_t *p;
- for (p=s+wcslen(s); p>=s && *p!=c; p--);
- return p>=s ? (wchar_t *)p : 0;
+ p = s+wcslen(s);
+ while (*p != c) {
+ if (p == s) return 0;
+ p--;
+ }
+ return (wchar_t *)p;
}
--
2.55.0
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