ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 227 insertions, 0 deletions

diff --git a/fs/afs/dir_search.c b/fs/afs/dir_search.c
new file mode 100644
index 000000000..104411c06
--- /dev/null
+++ b/fs/afs/dir_search.c
@@ -0,0 +1,227 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Search a directory's hash table.
+ *
+ * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * https://tools.ietf.org/html/draft-keiser-afs3-directory-object-00
+ */
+
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/iversion.h>
+#include "internal.h"
+#include "afs_fs.h"
+#include "xdr_fs.h"
+
+/*
+ * Calculate the name hash.
+ */
+unsigned int afs_dir_hash_name(const struct qstr *name)
+{
+	const unsigned char *p = name->name;
+	unsigned int hash = 0, i;
+	int bucket;
+
+	for (i = 0; i < name->len; i++)
+		hash = (hash * 173) + p[i];
+	bucket = hash & (AFS_DIR_HASHTBL_SIZE - 1);
+	if (hash > INT_MAX) {
+		bucket = AFS_DIR_HASHTBL_SIZE - bucket;
+		bucket &= (AFS_DIR_HASHTBL_SIZE - 1);
+	}
+	return bucket;
+}
+
+/*
+ * Reset a directory iterator.
+ */
+static bool afs_dir_reset_iter(struct afs_dir_iter *iter)
+{
+	unsigned long long i_size = i_size_read(&iter->dvnode->netfs.inode);
+	unsigned int nblocks;
+
+	/* Work out the maximum number of steps we can take. */
+	nblocks = umin(i_size / AFS_DIR_BLOCK_SIZE, AFS_DIR_MAX_BLOCKS);
+	if (!nblocks)
+		return false;
+	iter->loop_check = nblocks * (AFS_DIR_SLOTS_PER_BLOCK - AFS_DIR_RESV_BLOCKS);
+	iter->prev_entry = 0; /* Hash head is previous */
+	return true;
+}
+
+/*
+ * Initialise a directory iterator for looking up a name.
+ */
+bool afs_dir_init_iter(struct afs_dir_iter *iter, const struct qstr *name)
+{
+	iter->nr_slots = afs_dir_calc_slots(name->len);
+	iter->bucket = afs_dir_hash_name(name);
+	return afs_dir_reset_iter(iter);
+}
+
+/*
+ * Get a specific block.
+ */
+union afs_xdr_dir_block *afs_dir_find_block(struct afs_dir_iter *iter, size_t block)
+{
+	struct folio_queue *fq = iter->fq;
+	struct afs_vnode *dvnode = iter->dvnode;
+	struct folio *folio;
+	size_t blpos = block * AFS_DIR_BLOCK_SIZE;
+	size_t blend = (block + 1) * AFS_DIR_BLOCK_SIZE, fpos = iter->fpos;
+	int slot = iter->fq_slot;
+
+	_enter("%zx,%d", block, slot);
+
+	if (iter->block) {
+		kunmap_local(iter->block);
+		iter->block = NULL;
+	}
+
+	if (dvnode->directory_size < blend)
+		goto fail;
+
+	if (!fq || blpos < fpos) {
+		fq = dvnode->directory;
+		slot = 0;
+		fpos = 0;
+	}
+
+	/* Search the folio queue for the folio containing the block... */
+	for (; fq; fq = fq->next) {
+		for (; slot < folioq_count(fq); slot++) {
+			size_t fsize = folioq_folio_size(fq, slot);
+
+			if (blend <= fpos + fsize) {
+				/* ... and then return the mapped block. */
+				folio = folioq_folio(fq, slot);
+				if (WARN_ON_ONCE(folio_pos(folio) != fpos))
+					goto fail;
+				iter->fq = fq;
+				iter->fq_slot = slot;
+				iter->fpos = fpos;
+				iter->block = kmap_local_folio(folio, blpos - fpos);
+				return iter->block;
+			}
+			fpos += fsize;
+		}
+		slot = 0;
+	}
+
+fail:
+	iter->fq = NULL;
+	iter->fq_slot = 0;
+	afs_invalidate_dir(dvnode, afs_dir_invalid_edit_get_block);
+	return NULL;
+}
+
+/*
+ * Search through a directory bucket.
+ */
+int afs_dir_search_bucket(struct afs_dir_iter *iter, const struct qstr *name,
+			  struct afs_fid *_fid)
+{
+	const union afs_xdr_dir_block *meta;
+	unsigned int entry;
+	int ret = -ESTALE;
+
+	meta = afs_dir_find_block(iter, 0);
+	if (!meta)
+		return -ESTALE;
+
+	entry = ntohs(meta->meta.hashtable[iter->bucket & (AFS_DIR_HASHTBL_SIZE - 1)]);
+	_enter("%x,%x", iter->bucket, entry);
+
+	while (entry) {
+		const union afs_xdr_dir_block *block;
+		const union afs_xdr_dirent *dire;
+		unsigned int blnum = entry / AFS_DIR_SLOTS_PER_BLOCK;
+		unsigned int slot = entry % AFS_DIR_SLOTS_PER_BLOCK;
+		unsigned int resv = (blnum == 0 ? AFS_DIR_RESV_BLOCKS0 : AFS_DIR_RESV_BLOCKS);
+
+		_debug("search %x", entry);
+
+		if (slot < resv) {
+			kdebug("slot out of range h=%x rs=%2x sl=%2x-%2x",
+			       iter->bucket, resv, slot, slot + iter->nr_slots - 1);
+			goto bad;
+		}
+
+		block = afs_dir_find_block(iter, blnum);
+		if (!block)
+			goto bad;
+		dire = &block->dirents[slot];
+
+		if (slot + iter->nr_slots <= AFS_DIR_SLOTS_PER_BLOCK &&
+		    memcmp(dire->u.name, name->name, name->len) == 0 &&
+		    dire->u.name[name->len] == '\0') {
+			_fid->vnode  = ntohl(dire->u.vnode);
+			_fid->unique = ntohl(dire->u.unique);
+			ret = entry;
+			goto found;
+		}
+
+		iter->prev_entry = entry;
+		entry = ntohs(dire->u.hash_next);
+		if (!--iter->loop_check) {
+			kdebug("dir chain loop h=%x", iter->bucket);
+			goto bad;
+		}
+	}
+
+	ret = -ENOENT;
+found:
+	if (iter->block) {
+		kunmap_local(iter->block);
+		iter->block = NULL;
+	}
+
+bad:
+	if (ret == -ESTALE)
+		afs_invalidate_dir(iter->dvnode, afs_dir_invalid_iter_stale);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Search the appropriate hash chain in the contents of an AFS directory.
+ */
+int afs_dir_search(struct afs_vnode *dvnode, const struct qstr *name,
+		   struct afs_fid *_fid, afs_dataversion_t *_dir_version)
+{
+	struct afs_dir_iter iter = { .dvnode = dvnode, };
+	int ret, retry_limit = 3;
+
+	_enter("{%llu},,,", dvnode->netfs.inode.i_ino);
+
+	if (!afs_dir_init_iter(&iter, name))
+		return -ENOENT;
+	do {
+		if (--retry_limit < 0) {
+			pr_warn("afs_read_dir(): Too many retries\n");
+			ret = -ESTALE;
+			break;
+		}
+		ret = afs_read_dir(dvnode, NULL);
+		if (ret < 0) {
+			if (ret != -ESTALE)
+				break;
+			if (test_bit(AFS_VNODE_DELETED, &dvnode->flags)) {
+				ret = -ESTALE;
+				break;
+			}
+			continue;
+		}
+		*_dir_version = inode_peek_iversion_raw(&dvnode->netfs.inode);
+
+		ret = afs_dir_search_bucket(&iter, name, _fid);
+		up_read(&dvnode->validate_lock);
+		if (ret == -ESTALE)
+			afs_dir_reset_iter(&iter);
+	} while (ret == -ESTALE);
+
+	_leave(" = %d", ret);
+	return ret;
+}