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, 175 insertions, 0 deletions

diff --git a/sound/synth/util_mem.c b/sound/synth/util_mem.c
new file mode 100644
index 000000000..21893e561
--- /dev/null
+++ b/sound/synth/util_mem.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (C) 2000 Takashi Iwai <tiwai@suse.de>
+ *
+ *  Generic memory management routines for soundcard memory allocation
+ */
+
+#include <linux/mutex.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <sound/core.h>
+#include <sound/util_mem.h>
+
+MODULE_AUTHOR("Takashi Iwai");
+MODULE_DESCRIPTION("Generic memory management routines for soundcard memory allocation");
+MODULE_LICENSE("GPL");
+
+#define get_memblk(p)	list_entry(p, struct snd_util_memblk, list)
+
+/*
+ * create a new memory manager
+ */
+struct snd_util_memhdr *
+snd_util_memhdr_new(int memsize)
+{
+	struct snd_util_memhdr *hdr;
+
+	hdr = kzalloc_obj(*hdr);
+	if (hdr == NULL)
+		return NULL;
+	hdr->size = memsize;
+	mutex_init(&hdr->block_mutex);
+	INIT_LIST_HEAD(&hdr->block);
+
+	return hdr;
+}
+
+/*
+ * free a memory manager
+ */
+void snd_util_memhdr_free(struct snd_util_memhdr *hdr)
+{
+	struct list_head *p;
+
+	if (!hdr)
+		return;
+	/* release all blocks */
+	while ((p = hdr->block.next) != &hdr->block) {
+		list_del(p);
+		kfree(get_memblk(p));
+	}
+	kfree(hdr);
+}
+
+/*
+ * allocate a memory block (without mutex)
+ */
+struct snd_util_memblk *
+__snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size)
+{
+	struct snd_util_memblk *blk;
+	unsigned int units, prev_offset;
+	struct list_head *p;
+
+	if (snd_BUG_ON(!hdr || size <= 0))
+		return NULL;
+
+	/* word alignment */
+	units = size;
+	if (units & 1)
+		units++;
+	if (units > hdr->size)
+		return NULL;
+
+	/* look for empty block */
+	prev_offset = 0;
+	list_for_each(p, &hdr->block) {
+		blk = get_memblk(p);
+		if (blk->offset - prev_offset >= units)
+			goto __found;
+		prev_offset = blk->offset + blk->size;
+	}
+	if (hdr->size - prev_offset < units)
+		return NULL;
+
+__found:
+	return __snd_util_memblk_new(hdr, units, p->prev);
+}
+
+
+/*
+ * create a new memory block with the given size
+ * the block is linked next to prev
+ */
+struct snd_util_memblk *
+__snd_util_memblk_new(struct snd_util_memhdr *hdr, unsigned int units,
+		      struct list_head *prev)
+{
+	struct snd_util_memblk *blk;
+
+	blk = kmalloc(sizeof(struct snd_util_memblk) + hdr->block_extra_size,
+		      GFP_KERNEL);
+	if (blk == NULL)
+		return NULL;
+
+	if (prev == &hdr->block)
+		blk->offset = 0;
+	else {
+		struct snd_util_memblk *p = get_memblk(prev);
+		blk->offset = p->offset + p->size;
+	}
+	blk->size = units;
+	list_add(&blk->list, prev);
+	hdr->nblocks++;
+	hdr->used += units;
+	return blk;
+}
+
+
+/*
+ * allocate a memory block (with mutex)
+ */
+struct snd_util_memblk *
+snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size)
+{
+	guard(mutex)(&hdr->block_mutex);
+	return __snd_util_mem_alloc(hdr, size);
+}
+
+
+/*
+ * remove the block from linked-list and free resource
+ * (without mutex)
+ */
+void
+__snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk)
+{
+	list_del(&blk->list);
+	hdr->nblocks--;
+	hdr->used -= blk->size;
+	kfree(blk);
+}
+
+/*
+ * free a memory block (with mutex)
+ */
+int snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk)
+{
+	if (snd_BUG_ON(!hdr || !blk))
+		return -EINVAL;
+
+	guard(mutex)(&hdr->block_mutex);
+	__snd_util_mem_free(hdr, blk);
+	return 0;
+}
+
+/*
+ * return available memory size
+ */
+int snd_util_mem_avail(struct snd_util_memhdr *hdr)
+{
+	guard(mutex)(&hdr->block_mutex);
+	return hdr->size - hdr->used;
+}
+
+
+EXPORT_SYMBOL(snd_util_memhdr_new);
+EXPORT_SYMBOL(snd_util_memhdr_free);
+EXPORT_SYMBOL(snd_util_mem_alloc);
+EXPORT_SYMBOL(snd_util_mem_free);
+EXPORT_SYMBOL(snd_util_mem_avail);
+EXPORT_SYMBOL(__snd_util_mem_alloc);
+EXPORT_SYMBOL(__snd_util_mem_free);
+EXPORT_SYMBOL(__snd_util_memblk_new);