CVE-2026-97949configfs: unhash the dentry before dropping the item in rmdir

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b315d865660766d45ecdbf7433a4e3d36a554b3b
• https://git.kernel.org/stable/c/446720051d44eebaa81b33969173160057b73a33
• https://git.kernel.org/stable/c/5d7cbfb65e47cc71d5d94d87d5d0d1679080f3eb
• https://git.kernel.org/stable/c/925d8564f1b2d9b46c5ab63b9bc942cea006da9b
• https://git.kernel.org/stable/c/f06c2d26d1999d37e93299db0ecead04ca7d0b9f