[PATCH v2] expand: fix SIGBUS due to unaligned access

Natanael Copa
2026-01-16T20:56:57Z

Replace direct uint64_t dereference with memcpy() to avoid
SIGBUS on armv7 when p is not 8-byte aligned.

Fixes crashes in dash during IFS splitting on strict-alignment
architectures.

Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
---
src/expand.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

v2:
- Added a couple more instances of unaligned access.

diff --git a/src/expand.c b/src/expand.c
index 8c8bf0e..98b65ba 100644
--- a/src/expand.c
+++ b/src/expand.c
@@ -961,13 +961,14 @@ static size_t memtodest(const char *p, size_t len, int flags)
if (likely(!(flags & (expq >> 3 | expq >> 4 | expq >> 8) &
(QUOTES_ESC | EXP_MBCHAR)))) {
while (len >= 8) {
- uint64_t x = *(uint64_t *)(p + count);
+ uint64_t x;
+ memcpy(&x, p + count, sizeof(x));

if ((x | (x - 0x0101010101010101)) &
0x8080808080808080)
break;

- *(uint64_t *)(q + count) = x;
+ memcpy(q + count, &x, sizeof(x));

count += 8;
len -= 8;
@@ -1335,7 +1336,7 @@ ifsbreakup(char *string, int maxargs, struct arglist *arglist)
unsigned char b[8];
} x;

- x.qw = *(uint64_t *)p;
+ memcpy(&x.qw, p, sizeof(x.qw));

if ((x.qw & 0x8080808080808080))
break;
--
2.52.0