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/befs/inode.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 fs/befs/inode.c (limited to 'fs/befs/inode.c') diff --git a/fs/befs/inode.c b/fs/befs/inode.c new file mode 100644 index 000000000..791b46a6f --- /dev/null +++ b/fs/befs/inode.c @@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * inode.c + * + * Copyright (C) 2001 Will Dyson + */ + +#include + +#include "befs.h" +#include "inode.h" + +/* + * Validates the correctness of the befs inode + * Returns BEFS_OK if the inode should be used, otherwise + * returns BEFS_BAD_INODE + */ +int +befs_check_inode(struct super_block *sb, befs_inode *raw_inode, + befs_blocknr_t inode) +{ + u32 magic1 = fs32_to_cpu(sb, raw_inode->magic1); + befs_inode_addr ino_num = fsrun_to_cpu(sb, raw_inode->inode_num); + u32 flags = fs32_to_cpu(sb, raw_inode->flags); + + /* check magic header. */ + if (magic1 != BEFS_INODE_MAGIC1) { + befs_error(sb, + "Inode has a bad magic header - inode = %lu", + (unsigned long)inode); + return BEFS_BAD_INODE; + } + + /* + * Sanity check2: inodes store their own block address. Check it. + */ + if (inode != iaddr2blockno(sb, &ino_num)) { + befs_error(sb, "inode blocknr field disagrees with vfs " + "VFS: %lu, Inode %lu", (unsigned long) + inode, (unsigned long)iaddr2blockno(sb, &ino_num)); + return BEFS_BAD_INODE; + } + + /* + * check flag + */ + + if (!(flags & BEFS_INODE_IN_USE)) { + befs_error(sb, "inode is not used - inode = %lu", + (unsigned long)inode); + return BEFS_BAD_INODE; + } + + return BEFS_OK; +} -- cgit v1.3.1