configfs: pin the symlink target's dirent instead of chasing ->ci_dentry

Summary

In the Linux kernel, the following vulnerability has been resolved: configfs: pin the symlink target's dirent instead of chasing ->ci_dentry create_link() reads the target's configfs_dirent from item->ci_dentry->d_fsdata, relying on the item reference taken by get_target(). That reference pins the item, not its dentry: the dentry is pinned by DCACHE_PERSISTENT, which configfs_remove_dir() releases via simple_rmdir() while the item is still alive. A symlink racing with rmdir of its target can therefore find ->ci_dentry freed and its dirent released, triggering WARN_ON(!atomic_read(&sd->s_count)) in configfs_get(). Take the dirent in get_target() as well, under ->d_lock and atomically with the item reference, and pass it down to create_link(). A hashed dentry has not been killed yet, so its ->d_fsdata reference keeps the dirent alive there.

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 a44744454eafbc158e8c8e3ef8d207076410b195; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in 846ff40fd57a47e59a41f4e331ec3b34efaddc23; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in 4f54beb2e7f6d399396466682fba3539bcdcb414; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in d47c5de1cd6bfbe1067fc310bf90e4e00205e839; From 7063fbf2261194f72ee75afca67b3b38b554b5fa · fixed in a7c1290eef60711c10289c056ad32ed1f2b47b12

• 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