configfs: unhash the dentry before dropping the item in rmdir

Summary

In the Linux kernel, the following vulnerability has been resolved: configfs: unhash the dentry before dropping the item in rmdir configfs_get_config_item() treats a hashed dentry as proof that sd->s_element is a live config_item. configfs_rmdir() breaks that: simple_rmdir() leaves the dentry hashed, the last reference to the item is dropped right after, and the dentry is only unhashed by d_delete() once ->rmdir() has returned. configfs_symlink() resolves its target holding no lock on it, so get_target() can land in that window: BUG: KASAN: slab-use-after-free in config_item_get+0x26/0x90 get_target fs/configfs/symlink.c:128 [inline] configfs_symlink+0x4ab/0x1030 fs/configfs/symlink.c:185 Unhash in configfs_remove_dir(), while the item is still guaranteed to be there. A reference obtained just before that stays harmless, as create_link() rechecks CONFIGFS_USET_DROPPING, already set by configfs_detach_prep(). Both configfs_unregister_subsystem() paths d_drop() after detaching, so this only makes rmdir match them.

Timeline

1. Sep 25, 2026, 10:22 AM UTCCVE published
2. Oct 21, 2026, 12:53 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in b315d865660766d45ecdbf7433a4e3d36a554b3b; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in 446720051d44eebaa81b33969173160057b73a33; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in 5d7cbfb65e47cc71d5d94d87d5d0d1679080f3eb; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in 925d8564f1b2d9b46c5ab63b9bc942cea006da9b; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in f06c2d26d1999d37e93299db0ecead04ca7d0b9f

• Linux Linux

  2.6.16

• KernelLinux

  From 2.6.16 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.53; From 6.19.0 · fixed in 7.2.7

References 5