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, 77 insertions, 0 deletions

diff --git a/sound/firewire/packets-buffer.c b/sound/firewire/packets-buffer.c
new file mode 100644
index 000000000..2093a5fbd
--- /dev/null
+++ b/sound/firewire/packets-buffer.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * helpers for managing a buffer for many packets
+ *
+ * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
+ */
+
+#include <linux/firewire.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include "packets-buffer.h"
+
+/**
+ * iso_packets_buffer_init - allocates the memory for packets
+ * @b: the buffer structure to initialize
+ * @unit: the device at the other end of the stream
+ * @count: the number of packets
+ * @packet_size: the (maximum) size of a packet, in bytes
+ * @direction: %DMA_TO_DEVICE or %DMA_FROM_DEVICE
+ */
+int iso_packets_buffer_init(struct iso_packets_buffer *b, struct fw_unit *unit,
+			    unsigned int count, unsigned int packet_size,
+			    enum dma_data_direction direction)
+{
+	unsigned int packets_per_page, pages;
+	unsigned int i, page_index, offset_in_page;
+	void *p;
+	int err;
+
+	b->packets = kmalloc_objs(*b->packets, count);
+	if (!b->packets) {
+		err = -ENOMEM;
+		goto error;
+	}
+
+	packet_size = L1_CACHE_ALIGN(packet_size);
+	packets_per_page = PAGE_SIZE / packet_size;
+	if (WARN_ON(!packets_per_page)) {
+		err = -EINVAL;
+		goto err_packets;
+	}
+	pages = DIV_ROUND_UP(count, packets_per_page);
+
+	err = fw_iso_buffer_init(&b->iso_buffer, fw_parent_device(unit)->card,
+				 pages, direction);
+	if (err < 0)
+		goto err_packets;
+
+	for (i = 0; i < count; ++i) {
+		page_index = i / packets_per_page;
+		p = page_address(b->iso_buffer.pages[page_index]);
+		offset_in_page = (i % packets_per_page) * packet_size;
+		b->packets[i].buffer = p + offset_in_page;
+		b->packets[i].offset = page_index * PAGE_SIZE + offset_in_page;
+	}
+
+	return 0;
+
+err_packets:
+	kfree(b->packets);
+error:
+	return err;
+}
+EXPORT_SYMBOL(iso_packets_buffer_init);
+
+/**
+ * iso_packets_buffer_destroy - frees packet buffer resources
+ * @b: the buffer structure to free
+ * @unit: the device at the other end of the stream
+ */
+void iso_packets_buffer_destroy(struct iso_packets_buffer *b,
+				struct fw_unit *unit)
+{
+	fw_iso_buffer_destroy(&b->iso_buffer, fw_parent_device(unit)->card);
+	kfree(b->packets);
+}
+EXPORT_SYMBOL(iso_packets_buffer_destroy);