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, 124 insertions, 0 deletions

diff --git a/fs/squashfs/file_direct.c b/fs/squashfs/file_direct.c
new file mode 100644
index 000000000..2c3e809d6
--- /dev/null
+++ b/fs/squashfs/file_direct.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2013
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ */
+
+#include <linux/fs.h>
+#include <linux/vfs.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/pagemap.h>
+#include <linux/mutex.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs_fs_i.h"
+#include "squashfs.h"
+#include "page_actor.h"
+
+/* Read separately compressed datablock directly into page cache */
+int squashfs_readpage_block(struct folio *folio, u64 block, int bsize,
+		int expected)
+{
+	struct page *target_page = &folio->page;
+	struct inode *inode = folio->mapping->host;
+	struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
+	loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+	int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
+	loff_t start_index = folio->index & ~mask;
+	loff_t end_index = start_index | mask;
+	loff_t index;
+	int i, pages, bytes, res = -ENOMEM;
+	struct page **page, *last_page;
+	struct squashfs_page_actor *actor;
+	void *pageaddr;
+
+	if (end_index > file_end)
+		end_index = file_end;
+
+	pages = end_index - start_index + 1;
+
+	page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
+	if (page == NULL)
+		return res;
+
+	/* Try to grab all the pages covered by the Squashfs block */
+	for (i = 0, index = start_index; index <= end_index; index++) {
+		page[i] = (index == folio->index) ? target_page :
+			grab_cache_page_nowait(folio->mapping, index);
+
+		if (page[i] == NULL)
+			continue;
+
+		if (PageUptodate(page[i])) {
+			unlock_page(page[i]);
+			put_page(page[i]);
+			continue;
+		}
+
+		i++;
+	}
+
+	pages = i;
+
+	/*
+	 * Create a "page actor" which will kmap and kunmap the
+	 * page cache pages appropriately within the decompressor
+	 */
+	actor = squashfs_page_actor_init_special(msblk, page, pages, expected,
+						start_index << PAGE_SHIFT);
+	if (actor == NULL)
+		goto out;
+
+	/* Decompress directly into the page cache buffers */
+	res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
+
+	last_page = squashfs_page_actor_free(actor);
+
+	if (res < 0)
+		goto mark_errored;
+
+	if (res != expected || IS_ERR(last_page)) {
+		res = -EIO;
+		goto mark_errored;
+	}
+
+	/* Last page (if present) may have trailing bytes not filled */
+	bytes = res % PAGE_SIZE;
+	if (end_index == file_end && last_page && bytes) {
+		pageaddr = kmap_local_page(last_page);
+		memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
+		kunmap_local(pageaddr);
+	}
+
+	/* Mark pages as uptodate, unlock and release */
+	for (i = 0; i < pages; i++) {
+		flush_dcache_page(page[i]);
+		SetPageUptodate(page[i]);
+		unlock_page(page[i]);
+		if (page[i] != target_page)
+			put_page(page[i]);
+	}
+
+	kfree(page);
+
+	return 0;
+
+mark_errored:
+	/* Decompression failed.  Target_page is
+	 * dealt with by the caller
+	 */
+	for (i = 0; i < pages; i++) {
+		if (page[i] == NULL || page[i] == target_page)
+			continue;
+		flush_dcache_page(page[i]);
+		unlock_page(page[i]);
+		put_page(page[i]);
+	}
+
+out:
+	kfree(page);
+	return res;
+}