[PATCH v2] erofs-utils: lib: fix xattr crash in rebuild path when source has xattr

[Gao Xiang]

Hi Lucus,

On 2026/3/3 10:39, lishixian wrote:
> When rebuilding from source EROFS images, erofs_read_xattrs_from_disk()
> is called for inodes that have xattr. At that point inode->sbi points to
> the source image's sbi, which is opened read-only and never gets
> erofs_xattr_init(), so sbi->xamgr is NULL. get_xattritem(sbi) then
> dereferences xamgr and crashes with SIGSEGV.
> 
> Fix by using the build target's xamgr when initializing src's sbi.
> 
> Reported-by: Yixiao Chen <489679970 at qq.com>
> Fixes: https://github.com/erofs/erofs-utils/issues/42
> Signed-off-by: lishixian <lishixian8 at huawei.com>
> Reviewed-by: Yifan Zhao <zhaoyifan28 at huawei.com>

Can you confirm it that fixes your issue too?
I will merge this for the bandaid solution, but after erofs-utils 1.9.1
is released, rebuild and xattr codebase need to be fixed instead.

Thanks,
Gao Xiang

> ---
>   mkfs/main.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/mkfs/main.c b/mkfs/main.c
> index b84d1b4..58c18f9 100644
> --- a/mkfs/main.c
> +++ b/mkfs/main.c
> @@ -1735,7 +1735,9 @@ static int erofs_mkfs_rebuild_load_trees(struct erofs_inode *root)
>   	}
>   
>   	list_for_each_entry(src, &rebuild_src_list, list) {
> +		src->xamgr = g_sbi.xamgr;
>   		ret = erofs_rebuild_load_tree(root, src, datamode);
> +		src->xamgr = NULL;
>   		if (ret) {
>   			erofs_err("failed to load %s", src->devname);
>   			return ret;