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From 211264e46a2f1bc382a84435e904d1548de672b0 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Fri, 27 Sep 2013 13:09:46 -0400
Subject: [PATCH] fix buffer overflow in mbsrtowcs
issue reported by Michael Forney:
"If wn becomes 0 after processing a chunk of 4, mbsrtowcs currently
continues on, wrapping wn around to -1, causing the rest of the string
to be processed.
This resulted in buffer overruns if there was only space in ws for wn
wide characters."
the original patch submitted added an additional check for !wn after
the loop; to avoid extra branching, I instead just changed the wn>=4
check to wn>=5 to ensure that at least one slot remains after the
word-at-a-time loop runs. this should not slow down the tail
processing on real-world usage, since an extra slot that can't be
processed in the word-at-a-time loop is needed for the null
termination anyway.
---
src/multibyte/mbsrtowcs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/multibyte/mbsrtowcs.c b/src/multibyte/mbsrtowcs.c
index b9bbc33..066cce6 100644
--- a/src/multibyte/mbsrtowcs.c
+++ b/src/multibyte/mbsrtowcs.c
@@ -59,7 +59,7 @@ resume0:
return wn0;
}
if (*s-1u < 0x7f && (uintptr_t)s%4 == 0) {
- while (wn>=4 && !(( *(uint32_t*)s | *(uint32_t*)s-0x01010101) & 0x80808080)) {
+ while (wn>=5 && !(( *(uint32_t*)s | *(uint32_t*)s-0x01010101) & 0x80808080)) {
*ws++ = *s++;
*ws++ = *s++;
*ws++ = *s++;
--
1.8.4
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