[PATCH] libs/port/mbtowc: Convert 1 character at a time if dst overlaps into src
Gabriel Ivăncescu
gabrielopcode at gmail.com
Fri Aug 24 13:32:38 CDT 2018
Some applications partially overlap the two buffers. For such rare corner
cases, do a single check so that there will be no performance regressions,
as unsigned operations are defined to wrap around.
Bug discovered by Jason Edmeades, revised from bug report.
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=38558
Signed-off-by: Gabriel Ivăncescu <gabrielopcode at gmail.com>
---
libs/port/mbtowc.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/libs/port/mbtowc.c b/libs/port/mbtowc.c
index 4977c82..6ed2c2e 100644
--- a/libs/port/mbtowc.c
+++ b/libs/port/mbtowc.c
@@ -65,6 +65,17 @@ static inline int mbstowcs_sbcs( const struct sbcs_table *table, int flags,
ret = -1;
}
+ /* dst can overlap into src, in which case we need to handle 1 char at a time,
+ but when src < dst, there is no issue no matter how many we handle at once */
+ if ((UINT_PTR) ((UINT_PTR)src - (UINT_PTR)dst) < srclen * sizeof(*dst))
+ {
+ do
+ *dst++ = cp2uni[*src++];
+ while (--srclen);
+ return ret;
+ }
+
+ /* dst doesn't overlap into src */
for (;;)
{
switch(srclen)
--
1.9.1
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