While investigating a sporadic crash issue relating to variable substitution in
Alpine Linux, we managed to get a reliable crash when building BusyBox with
ASan,
due to the source and destination overlapping for mempcpy, which resulted in
sporadic data corruption outside ASan.
Per POSIX, memcpy is not allowed to overlap source and destination, as mempcpy
is a GNU-specific extension to mempcpy, the same semantics can be assumed.
Accordingly, we use memmove instead, which does not have this limitation.
Signed-off-by: Ariadne Conill <aria...@dereferenced.org>
---
shell/ash.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/shell/ash.c b/shell/ash.c
index adb0f223a..6f256d4c3 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -7187,7 +7187,7 @@ subevalvar(char *start, char *str, int strloc,
len = orig_len - pos;
if (!quotes) {
- loc = mempcpy(startp, startp + pos, len);
+ loc = memmove(startp, startp + pos, len);
} else {
for (vstr = startp; pos != 0; pos--) {
if ((unsigned char)*vstr == CTLESC)
--
2.35.1
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