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, 196 insertions, 0 deletions

diff --git a/fs/squashfs/xz_wrapper.c b/fs/squashfs/xz_wrapper.c
new file mode 100644
index 000000000..0a4ff3ec9
--- /dev/null
+++ b/fs/squashfs/xz_wrapper.c
@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Squashfs - a compressed read only filesystem for Linux
+ *
+ * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ *
+ * xz_wrapper.c
+ */
+
+
+#include <linux/mutex.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/xz.h>
+#include <linux/bitops.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+struct squashfs_xz {
+	struct xz_dec *state;
+	struct xz_buf buf;
+};
+
+struct disk_comp_opts {
+	__le32 dictionary_size;
+	__le32 flags;
+};
+
+struct comp_opts {
+	int dict_size;
+};
+
+static void *squashfs_xz_comp_opts(struct squashfs_sb_info *msblk,
+	void *buff, int len)
+{
+	struct disk_comp_opts *comp_opts = buff;
+	struct comp_opts *opts;
+	int err = 0, n;
+
+	opts = kmalloc_obj(*opts);
+	if (opts == NULL) {
+		err = -ENOMEM;
+		goto out2;
+	}
+
+	if (comp_opts) {
+		/* check compressor options are the expected length */
+		if (len < sizeof(*comp_opts)) {
+			err = -EIO;
+			goto out;
+		}
+
+		opts->dict_size = le32_to_cpu(comp_opts->dictionary_size);
+
+		/* the dictionary size should be 2^n or 2^n+2^(n+1) */
+		n = ffs(opts->dict_size) - 1;
+		if (opts->dict_size != (1 << n) && opts->dict_size != (1 << n) +
+						(1 << (n + 1))) {
+			err = -EIO;
+			goto out;
+		}
+	} else
+		/* use defaults */
+		opts->dict_size = max_t(int, msblk->block_size,
+							SQUASHFS_METADATA_SIZE);
+
+	return opts;
+
+out:
+	kfree(opts);
+out2:
+	return ERR_PTR(err);
+}
+
+
+static void *squashfs_xz_init(struct squashfs_sb_info *msblk, void *buff)
+{
+	struct comp_opts *comp_opts = buff;
+	struct squashfs_xz *stream;
+	int err;
+
+	stream = kmalloc_obj(*stream);
+	if (stream == NULL) {
+		err = -ENOMEM;
+		goto failed;
+	}
+
+	stream->state = xz_dec_init(XZ_PREALLOC, comp_opts->dict_size);
+	if (stream->state == NULL) {
+		kfree(stream);
+		err = -ENOMEM;
+		goto failed;
+	}
+
+	return stream;
+
+failed:
+	ERROR("Failed to initialise xz decompressor\n");
+	return ERR_PTR(err);
+}
+
+
+static void squashfs_xz_free(void *strm)
+{
+	struct squashfs_xz *stream = strm;
+
+	if (stream) {
+		xz_dec_end(stream->state);
+		kfree(stream);
+	}
+}
+
+
+static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void *strm,
+	struct bio *bio, int offset, int length,
+	struct squashfs_page_actor *output)
+{
+	struct bvec_iter_all iter_all = {};
+	struct bio_vec *bvec = bvec_init_iter_all(&iter_all);
+	int total = 0, error = 0;
+	struct squashfs_xz *stream = strm;
+
+	xz_dec_reset(stream->state);
+	stream->buf.in_pos = 0;
+	stream->buf.in_size = 0;
+	stream->buf.out_pos = 0;
+	stream->buf.out_size = PAGE_SIZE;
+	stream->buf.out = squashfs_first_page(output);
+	if (IS_ERR(stream->buf.out)) {
+		error = PTR_ERR(stream->buf.out);
+		goto finish;
+	}
+
+	for (;;) {
+		enum xz_ret xz_err;
+
+		if (stream->buf.in_pos == stream->buf.in_size) {
+			const void *data;
+			int avail;
+
+			if (!bio_next_segment(bio, &iter_all)) {
+				/* XZ_STREAM_END must be reached. */
+				error = -EIO;
+				break;
+			}
+
+			avail = min(length, ((int)bvec->bv_len) - offset);
+			data = bvec_virt(bvec);
+			length -= avail;
+			stream->buf.in = data + offset;
+			stream->buf.in_size = avail;
+			stream->buf.in_pos = 0;
+			offset = 0;
+		}
+
+		if (stream->buf.out_pos == stream->buf.out_size) {
+			stream->buf.out = squashfs_next_page(output);
+			if (IS_ERR(stream->buf.out)) {
+				error = PTR_ERR(stream->buf.out);
+				break;
+			} else if (stream->buf.out != NULL) {
+				stream->buf.out_pos = 0;
+				total += PAGE_SIZE;
+			}
+		}
+
+		xz_err = xz_dec_run(stream->state, &stream->buf);
+		if (xz_err == XZ_STREAM_END)
+			break;
+		if (xz_err != XZ_OK) {
+			error = -EIO;
+			break;
+		}
+	}
+
+finish:
+	squashfs_finish_page(output);
+
+	return error ? error : total + stream->buf.out_pos;
+}
+
+const struct squashfs_decompressor squashfs_xz_comp_ops = {
+	.init = squashfs_xz_init,
+	.comp_opts = squashfs_xz_comp_opts,
+	.free = squashfs_xz_free,
+	.decompress = squashfs_xz_uncompress,
+	.id = XZ_COMPRESSION,
+	.name = "xz",
+	.alloc_buffer = 1,
+	.supported = 1
+};