CVE-2026-74342 Detail
Received
This CVE record has recently been published to the CVE List and has been included within the NVD dataset. DescriptionIn the Linux kernel, the following vulnerability has been resolved: kernfs: link kn to its parent before the LSM init hook After commit 12e9e3cd03b5 ("simpe_xattr: use per-sb cache"), kernfs_xattr_set() and kernfs_xattr_get() compute the cache via kernfs_root(kn) before any other check. kernfs_root(kn) walks kn->__parent first and falls back to kn->dir.root, both of which are NULL on a freshly kmem_cache_zalloc()'d kn. kn->__parent was being set in kernfs_new_node() after __kernfs_new_node() returned, and kn->dir.root is set even later by kernfs_create_dir_ns() / kernfs_create_empty_dir(). The LSM kernfs_init_security hook is invoked from inside __kernfs_new_node(), before either field has been initialized. selinux_kernfs_init_security() ends with kernfs_xattr_set(kn, XATTR_NAME_SELINUX, ...). kernfs_root(kn) then returns NULL, and &((struct kernfs_root *)NULL)->xa_cache evaluates to offsetof(struct kernfs_root, xa_cache) which faults: BUG: kernel NULL pointer dereference, address: 00000000000000e0 RIP: 0010:simple_xattr_set+0x27/0x8b0 Call Trace: kernfs_xattr_set+0x63/0xb0 selinux_kernfs_init_security+0x13b/0x270 security_kernfs_init_security+0x36/0xc0 __kernfs_new_node+0x182/0x290 kernfs_new_node+0x80/0xc0 kernfs_create_dir_ns+0x2b/0xa0 cgroup_create+0x116/0x380 cgroup_mkdir+0x7c/0x1a0 Reproduces deterministically at PID 1 (systemd) on an SELinux-enabled distro. The first cgroup mkdir under /sys/fs/cgroup with a labelled parent panics the kernel. The LSM hook's contract is that the kn_dir argument is the parent of the new kn, so kn->__parent should already point at kn_dir when the hook runs. Move kernfs_get(parent) and rcu_assign_pointer of kn->__parent from kernfs_new_node() into __kernfs_new_node() right before the security hook, and unwind the parent reference on the err_out4 path. kernfs_root(kn) then takes its parent branch during the hook and returns parent->dir.root, which is the correct root. This also closes the same-shape latent bug in kernfs_xattr_get() (which today is hidden only by kernfs_iattrs_noalloc() returning NULL on a fresh kn). Metrics
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Weakness Enumeration
Quick InfoCVE Dictionary Entry:CVE-2026-74342 NVD Published Date: 08/15/2026 NVD Last Modified: 08/15/2026 Source: kernel.org |
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