[PATCH] erofs-utils: lib: fix sorting shared xattrs

[PATCH] erofs-utils: lib: fix sorting shared xattrs

[Sheng Yong via Linux-erofs]

The length of xattr_item->kvbuf is calculated by EROFS_XATTR_KVSIZE,
and the key part has a trailing '\0' before the value part. When qsort
compares two xattr_items, the key-value length should be calculated by
EROFS_XATTR_KVSIZE, and use memcmp instead of strncmp to avoid key-value
string being cut by '\0'.

Fixes: 5df285cf405d ("erofs-utils: lib: refactor extended attribute name prefixes")
Signed-off-by: Sheng Yong <shengyong@oppo.com>
---
 lib/xattr.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/xattr.c b/lib/xattr.c
index 651657f979cc..1dbb6e7bde49 100644
--- a/lib/xattr.c
+++ b/lib/xattr.c
@@ -794,10 +794,10 @@ static int comp_shared_xattr_item(const void *a, const void *b)
 
 	ia = *((const struct xattr_item **)a);
 	ib = *((const struct xattr_item **)b);
-	la = ia->len[0] + ia->len[1];
-	lb = ib->len[0] + ib->len[1];
+	la = EROFS_XATTR_KVSIZE(ia->len);
+	lb = EROFS_XATTR_KVSIZE(ib->len);
 
-	ret = strncmp(ia->kvbuf, ib->kvbuf, min(la, lb));
+	ret = memcmp(ia->kvbuf, ib->kvbuf, min(la, lb));
 	if (ret != 0)
 		return ret;
 
-- 
2.40.1

Re: [PATCH] erofs-utils: lib: fix sorting shared xattrs

[Gao Xiang via Linux-erofs]

Hi Yong,

On Fri, Sep 13, 2024 at 10:35:42PM +0800, Sheng Yong via Linux-erofs wrote:
> The length of xattr_item->kvbuf is calculated by EROFS_XATTR_KVSIZE,
> and the key part has a trailing '\0' before the value part. When qsort
> compares two xattr_items, the key-value length should be calculated by
> EROFS_XATTR_KVSIZE, and use memcmp instead of strncmp to avoid key-value
> string being cut by '\0'.
> 
> Fixes: 5df285cf405d ("erofs-utils: lib: refactor extended attribute name prefixes")
> Signed-off-by: Sheng Yong <shengyong@oppo.com>

Yeah, good catch! And many thanks for fixing this!
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Thanks,
Gao Xiang