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/9p/fid.h | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 fs/9p/fid.h (limited to 'fs/9p/fid.h') diff --git a/fs/9p/fid.h b/fs/9p/fid.h new file mode 100644 index 000000000..0d6138bee --- /dev/null +++ b/fs/9p/fid.h @@ -0,0 +1,61 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * V9FS FID Management + * + * Copyright (C) 2005 by Eric Van Hensbergen + */ +#ifndef FS_9P_FID_H +#define FS_9P_FID_H +#include +#include "v9fs.h" + +struct p9_fid *v9fs_fid_find_inode(struct inode *inode, bool want_writeable, + kuid_t uid, bool any); +struct p9_fid *v9fs_fid_lookup(struct dentry *dentry); +static inline struct p9_fid *v9fs_parent_fid(struct dentry *dentry) +{ + return v9fs_fid_lookup(dentry->d_parent); +} +void v9fs_fid_add(struct dentry *dentry, struct p9_fid **fid); +void v9fs_open_fid_add(struct inode *inode, struct p9_fid **fid); +static inline struct p9_fid *clone_fid(struct p9_fid *fid) +{ + return IS_ERR(fid) ? fid : p9_client_walk(fid, 0, NULL, 1); +} +static inline struct p9_fid *v9fs_fid_clone(struct dentry *dentry) +{ + struct p9_fid *fid, *nfid; + + fid = v9fs_fid_lookup(dentry); + if (!fid || IS_ERR(fid)) + return fid; + + nfid = clone_fid(fid); + p9_fid_put(fid); + return nfid; +} +/** + * v9fs_fid_addmodes - add cache flags to fid mode (for client use only) + * @fid: fid to augment + * @s_flags: session info mount flags + * @s_cache: session info cache flags + * @f_flags: unix open flags + * + * make sure mode reflects flags of underlying mounts + * also qid.version == 0 reflects a synthetic or legacy file system + * NOTE: these are set after open so only reflect 9p client not + * underlying file system on server. + */ +static inline void v9fs_fid_add_modes(struct p9_fid *fid, unsigned int s_flags, + unsigned int s_cache, unsigned int f_flags) +{ + if ((!s_cache) || + ((fid->qid.version == 0) && !(s_flags & V9FS_IGNORE_QV)) || + (s_flags & V9FS_DIRECT_IO) || (f_flags & O_DIRECT)) { + fid->mode |= P9L_DIRECT; /* no read or write cache */ + } else if ((!(s_cache & CACHE_WRITEBACK)) || + (f_flags & O_DSYNC) || (s_flags & V9FS_SYNC)) { + fid->mode |= P9L_NOWRITECACHE; + } +} +#endif -- cgit v1.3.1