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/nfs/symlink.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 fs/nfs/symlink.c (limited to 'fs/nfs/symlink.c') diff --git a/fs/nfs/symlink.c b/fs/nfs/symlink.c new file mode 100644 index 000000000..74a072896 --- /dev/null +++ b/fs/nfs/symlink.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/nfs/symlink.c + * + * Copyright (C) 1992 Rick Sladkey + * + * Optimization changes Copyright (C) 1994 Florian La Roche + * + * Jun 7 1999, cache symlink lookups in the page cache. -DaveM + * + * nfs symlink handling code + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +/* Symlink caching in the page cache is even more simplistic + * and straight-forward than readdir caching. + */ + +static int nfs_symlink_filler(struct file *file, struct folio *folio) +{ + struct inode *inode = folio->mapping->host; + int error; + + error = NFS_PROTO(inode)->readlink(inode, &folio->page, 0, PAGE_SIZE); + folio_end_read(folio, error == 0); + return error; +} + +static const char *nfs_get_link(struct dentry *dentry, + struct inode *inode, + struct delayed_call *done) +{ + struct folio *folio; + void *err; + + if (!dentry) { + err = ERR_PTR(nfs_revalidate_mapping_rcu(inode)); + if (err) + return err; + folio = filemap_get_folio(inode->i_mapping, 0); + if (IS_ERR(folio)) + return ERR_PTR(-ECHILD); + if (!folio_test_uptodate(folio)) { + folio_put(folio); + return ERR_PTR(-ECHILD); + } + } else { + err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping)); + if (err) + return err; + folio = read_cache_folio(&inode->i_data, 0, nfs_symlink_filler, + NULL); + if (IS_ERR(folio)) + return ERR_CAST(folio); + } + set_delayed_call(done, page_put_link, folio); + return folio_address(folio); +} + +/* + * symlinks can't do much... + */ +const struct inode_operations nfs_symlink_inode_operations = { + .get_link = nfs_get_link, + .getattr = nfs_getattr, + .setattr = nfs_setattr, + .fileattr_get = nfs_fileattr_get, +}; -- cgit v1.3.1