From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- fs/ecryptfs/dentry.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 fs/ecryptfs/dentry.c (limited to 'fs/ecryptfs/dentry.c') diff --git a/fs/ecryptfs/dentry.c b/fs/ecryptfs/dentry.c new file mode 100644 index 000000000..6648a924e --- /dev/null +++ b/fs/ecryptfs/dentry.c @@ -0,0 +1,76 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * eCryptfs: Linux filesystem encryption layer + * + * Copyright (C) 1997-2003 Erez Zadok + * Copyright (C) 2001-2003 Stony Brook University + * Copyright (C) 2004-2006 International Business Machines Corp. + * Author(s): Michael A. Halcrow + */ + +#include +#include +#include +#include +#include +#include "ecryptfs_kernel.h" + +/** + * ecryptfs_d_revalidate - revalidate an ecryptfs dentry + * @dir: inode of expected parent + * @name: expected name + * @dentry: dentry to revalidate + * @flags: lookup flags + * + * Called when the VFS needs to revalidate a dentry. This + * is called whenever a name lookup finds a dentry in the + * dcache. Most filesystems leave this as NULL, because all their + * dentries in the dcache are valid. + * + * Returns 1 if valid, 0 otherwise. + * + */ +static int ecryptfs_d_revalidate(struct inode *dir, const struct qstr *name, + struct dentry *dentry, unsigned int flags) +{ + struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry); + int rc = 1; + + if (flags & LOOKUP_RCU) + return -ECHILD; + + if (lower_dentry->d_flags & DCACHE_OP_REVALIDATE) { + struct inode *lower_dir = ecryptfs_inode_to_lower(dir); + struct name_snapshot n; + + take_dentry_name_snapshot(&n, lower_dentry); + rc = lower_dentry->d_op->d_revalidate(lower_dir, &n.name, + lower_dentry, flags); + release_dentry_name_snapshot(&n); + } + + if (d_really_is_positive(dentry)) { + struct inode *inode = d_inode(dentry); + + fsstack_copy_attr_all(inode, ecryptfs_inode_to_lower(inode)); + if (!inode->i_nlink) + return 0; + } + return rc; +} + +/** + * ecryptfs_d_release + * @dentry: The ecryptfs dentry + * + * Called when a dentry is really deallocated. + */ +static void ecryptfs_d_release(struct dentry *dentry) +{ + dput(dentry->d_fsdata); +} + +const struct dentry_operations ecryptfs_dops = { + .d_revalidate = ecryptfs_d_revalidate, + .d_release = ecryptfs_d_release, +}; -- cgit v1.3.1