path: root/src/multibyte/mbsrtowcs.c
diff options
authorRich Felker <>2013-09-27 13:09:46 -0400
committerRich Felker <>2013-09-27 13:09:46 -0400
commit211264e46a2f1bc382a84435e904d1548de672b0 (patch)
tree86c29e9aabbcc1b713cfc2da388fc0c928a1ce1c /src/multibyte/mbsrtowcs.c
parente1f1df9c743af60c0e6271fcd78b59dbfd72d8ad (diff)
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.
Diffstat (limited to 'src/multibyte/mbsrtowcs.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/src/multibyte/mbsrtowcs.c b/src/multibyte/mbsrtowcs.c
index b9bbc33d..066cce60 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++;