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, 125 insertions, 0 deletions

diff --git a/fs/btrfs/accessors.c b/fs/btrfs/accessors.c
new file mode 100644
index 000000000..1248aa253
--- /dev/null
+++ b/fs/btrfs/accessors.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ */
+
+#include <linux/unaligned.h>
+#include "messages.h"
+#include "extent_io.h"
+#include "fs.h"
+#include "accessors.h"
+
+static void __cold report_setget_bounds(const struct extent_buffer *eb,
+					const void *ptr, unsigned off, int size)
+{
+	unsigned long member_offset = (unsigned long)ptr + off;
+
+	btrfs_warn(eb->fs_info,
+		   "bad eb member %s: ptr 0x%lx start %llu member offset %lu size %d",
+		   (member_offset > eb->len ? "start" : "end"),
+		   (unsigned long)ptr, eb->start, member_offset, size);
+}
+
+/* Copy bytes from @src1 and @src2 to @dest. */
+static __always_inline void memcpy_split_src(char *dest, const char *src1,
+					     const char *src2, const size_t len1,
+					     const size_t total)
+{
+	memcpy(dest, src1, len1);
+	memcpy(dest + len1, src2, total - len1);
+}
+
+/*
+ * Macro templates that define helpers to read/write extent buffer data of a
+ * given size, that are also used via ctree.h for access to item members by
+ * specialized helpers.
+ *
+ * Generic helpers:
+ * - btrfs_set_8 (for 8/16/32/64)
+ * - btrfs_get_8 (for 8/16/32/64)
+ *
+ * The set/get functions handle data spanning two pages transparently, in case
+ * metadata block size is larger than page.  Every pointer to metadata items is
+ * an offset into the extent buffer page array, cast to a specific type.  This
+ * gives us all the type checking.
+ *
+ * The extent buffer pages stored in the array folios may not form a contiguous
+ * physical range, but the API functions assume the linear offset to the range
+ * from 0 to metadata node size.
+ */
+
+#define DEFINE_BTRFS_SETGET_BITS(bits)					\
+u##bits btrfs_get_##bits(const struct extent_buffer *eb,		\
+			 const void *ptr, unsigned long off)		\
+{									\
+	const unsigned long member_offset = (unsigned long)ptr + off;	\
+	const unsigned long idx = get_eb_folio_index(eb, member_offset);\
+	const unsigned long oif = get_eb_offset_in_folio(eb,		\
+							 member_offset);\
+	char *kaddr = folio_address(eb->folios[idx]) + oif;		\
+	const int part = eb->folio_size - oif;				\
+	u8 lebytes[sizeof(u##bits)];					\
+									\
+	if (unlikely(member_offset + sizeof(u##bits) > eb->len)) {	\
+		report_setget_bounds(eb, ptr, off, sizeof(u##bits));	\
+		return 0;						\
+	}								\
+	if (INLINE_EXTENT_BUFFER_PAGES == 1 || sizeof(u##bits) == 1 ||	\
+	    likely(sizeof(u##bits) <= part))				\
+		return get_unaligned_le##bits(kaddr);			\
+									\
+	if (sizeof(u##bits) == 2) {					\
+		lebytes[0] = *kaddr;					\
+		kaddr = folio_address(eb->folios[idx + 1]);		\
+		lebytes[1] = *kaddr;					\
+	} else {							\
+		memcpy_split_src(lebytes, kaddr,			\
+				 folio_address(eb->folios[idx + 1]),	\
+				 part, sizeof(u##bits));		\
+	}								\
+	return get_unaligned_le##bits(lebytes);				\
+}									\
+void btrfs_set_##bits(const struct extent_buffer *eb, void *ptr,	\
+		      unsigned long off, u##bits val)			\
+{									\
+	const unsigned long member_offset = (unsigned long)ptr + off;	\
+	const unsigned long idx = get_eb_folio_index(eb, member_offset);\
+	const unsigned long oif = get_eb_offset_in_folio(eb,		\
+							 member_offset);\
+	char *kaddr = folio_address(eb->folios[idx]) + oif;		\
+	const int part = eb->folio_size - oif;				\
+	u8 lebytes[sizeof(u##bits)];					\
+									\
+	if (unlikely(member_offset + sizeof(u##bits) > eb->len)) {	\
+		report_setget_bounds(eb, ptr, off, sizeof(u##bits));	\
+		return;							\
+	}								\
+	if (INLINE_EXTENT_BUFFER_PAGES == 1 || sizeof(u##bits) == 1 ||	\
+	    likely(sizeof(u##bits) <= part)) {				\
+		put_unaligned_le##bits(val, kaddr);			\
+		return;							\
+	}								\
+	put_unaligned_le##bits(val, lebytes);				\
+	if (sizeof(u##bits) == 2) {					\
+		*kaddr = lebytes[0];					\
+		kaddr = folio_address(eb->folios[idx + 1]);		\
+		*kaddr = lebytes[1];					\
+	} else {							\
+		memcpy(kaddr, lebytes, part);				\
+		kaddr = folio_address(eb->folios[idx + 1]);		\
+		memcpy(kaddr, lebytes + part, sizeof(u##bits) - part);	\
+	}								\
+}
+
+DEFINE_BTRFS_SETGET_BITS(8)
+DEFINE_BTRFS_SETGET_BITS(16)
+DEFINE_BTRFS_SETGET_BITS(32)
+DEFINE_BTRFS_SETGET_BITS(64)
+
+void btrfs_node_key(const struct extent_buffer *eb,
+		    struct btrfs_disk_key *disk_key, int nr)
+{
+	unsigned long ptr = btrfs_node_key_ptr_offset(eb, nr);
+	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
+		       struct btrfs_key_ptr, key, disk_key);
+}