[PATCH v2] erofs: harden h_shared_count in erofs_init_inode_xattrs()

Utkal Singh
2026-03-17T15:24:52Z

`u8 h_shared_count` indicates the shared xattr count of an inode. It is
read from the on-disk xattr ibody header, which should be corrupted if
the size of the shared xattr array exceeds the space available in
`xattr_isize`.

It does not cause harmful consequence (e.g. crashes), since the image is
already considered corrupted, it indeed results in the silent processing
of garbage metadata.

Let's harden it to report -EFSCORRUPTED earlier.

Signed-off-by: Utkal Singh <singhutkal015@gmail.com>
---
fs/erofs/xattr.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
index c411df5d9dfc..aaac37c6bb78 100644
--- a/fs/erofs/xattr.c
+++ b/fs/erofs/xattr.c
@@ -85,6 +85,14 @@ static int erofs_init_inode_xattrs(struct inode *inode)
}
vi->xattr_name_filter = le32_to_cpu(ih->h_name_filter);
vi->xattr_shared_count = ih->h_shared_count;
+ if ((u32)vi->xattr_shared_count * sizeof(__le32) >
+ vi->xattr_isize - sizeof(struct erofs_xattr_ibody_header)) {
+ erofs_err(sb, "invalid h_shared_count %u in nid %llu",
+ vi->xattr_shared_count, vi->nid);
+ erofs_put_metabuf(&buf);
+ ret = -EFSCORRUPTED;
+ goto out_unlock;
+ }
vi->xattr_shared_xattrs = kmalloc_objs(uint, vi->xattr_shared_count);
if (!vi->xattr_shared_xattrs) {
erofs_put_metabuf(&buf);
--
2.43.0