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. v2: Forgot to emulate mempcpy's dest+size return value, fixed. Signed-off-by: Ariadne Conill <[email protected]> --- shell/ash.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/shell/ash.c b/shell/ash.c index adb0f223a..056954059 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) + len; } else { for (vstr = startp; pos != 0; pos--) { if ((unsigned char)*vstr == CTLESC) -- 2.35.1 _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
