Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: kernfs: fix xattr race condition with multiple superblocks Multiple superblocks with different namespaces can share the same kernfs_node when kernfs_test_super() finds a matching root but different namespace. This means multiple inodes from different superblocks can reference the same kernfs_node->iattr->xattrs structure. The VFS layer only holds per-inode locks during xattr operations, which is insufficient to serialize concurrent xattr modifications on the shared kernfs_node. This can lead to race conditions in simple_xattr_set() where the lookup->replace/remove sequence is not atomic with respect to operations from other superblocks. Fix this by protecting xattr operations with the existing hashed kernfs_locks->open_file_mutex[] array, which is already used to protect per-node open file data. The hashed mutex array provides scalable per-node serialization (scaled by CPU count, up to 1024 locks on 32+ CPU systems) with zero memory overhead. Changes: - Rename open_file_mutex[] to node_mutex[] to reflect dual purpose - Add kernfs_node_lock_ptr() and kernfs_node_lock() helpers - Protect simple_xattr_set() calls in kernfs_xattr_set() and kernfs_vfs_user_xattr_set() with the hashed mutex - Update file.c to use new helpers via compatibility wrappers - Update documentation to explain the extended lock usage
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected b32c4a213698ab351b44da2fd1b2a5976c7fa033 before bf53db51359939755084d08156684ed649489592; affected b32c4a213698ab351b44da2fd1b2a5976c7fa033 before 6a07814ff643b5c8e1353d8c6229f52fde205cde |
| Linux / Linux | affected 7.1; unaffected 0 before 7.1; unaffected 7.1.5 through 7.1.*; unaffected 7.2 through * |
CWE
No CWE identifiers supplied.