dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel()grafted

When dma_device_put() drops the last reference on chan->device->ref,
dma_device_release() runs and may free the dma_device along with its
channels.

dma_chan_put() then still reads chan->device->owner via
dma_chan_to_owner() for the trailing module_put(). KASAN catches it:

	slab-use-after-free in dma_chan_put+0x3e6/0x4c0
	Read of size 8 by task insmod/6319
	Freed by task 6319:
	  kfree+0x225/0x470
	  dma_chan_put+0x395/0x4c0
	  dmaengine_put+0xf8/0x160

Cache the module owner in dma_chan_put() before the put so the trailing
module_put() does not need chan->device.

Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 146 insertions, 0 deletions

diff --git a/fs/squashfs/lz4_wrapper.c b/fs/squashfs/lz4_wrapper.c
new file mode 100644
index 000000000..1646bbee2
--- /dev/null
+++ b/fs/squashfs/lz4_wrapper.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2013, 2014
+ * Phillip Lougher <phillip@squashfs.org.uk>
+ */
+
+#include <linux/bio.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/lz4.h>
+
+#include "squashfs_fs.h"
+#include "squashfs_fs_sb.h"
+#include "squashfs.h"
+#include "decompressor.h"
+#include "page_actor.h"
+
+#define LZ4_LEGACY	1
+
+struct lz4_comp_opts {
+	__le32 version;
+	__le32 flags;
+};
+
+struct squashfs_lz4 {
+	void *input;
+	void *output;
+};
+
+
+static void *lz4_comp_opts(struct squashfs_sb_info *msblk,
+	void *buff, int len)
+{
+	struct lz4_comp_opts *comp_opts = buff;
+
+	/* LZ4 compressed filesystems always have compression options */
+	if (comp_opts == NULL || len < sizeof(*comp_opts))
+		return ERR_PTR(-EIO);
+
+	if (le32_to_cpu(comp_opts->version) != LZ4_LEGACY) {
+		/* LZ4 format currently used by the kernel is the 'legacy'
+		 * format */
+		ERROR("Unknown LZ4 version\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	return NULL;
+}
+
+
+static void *lz4_init(struct squashfs_sb_info *msblk, void *buff)
+{
+	int block_size = max_t(int, msblk->block_size, SQUASHFS_METADATA_SIZE);
+	struct squashfs_lz4 *stream;
+
+	stream = kzalloc_obj(*stream);
+	if (stream == NULL)
+		goto failed;
+	stream->input = vmalloc(block_size);
+	if (stream->input == NULL)
+		goto failed2;
+	stream->output = vmalloc(block_size);
+	if (stream->output == NULL)
+		goto failed3;
+
+	return stream;
+
+failed3:
+	vfree(stream->input);
+failed2:
+	kfree(stream);
+failed:
+	ERROR("Failed to initialise LZ4 decompressor\n");
+	return ERR_PTR(-ENOMEM);
+}
+
+
+static void lz4_free(void *strm)
+{
+	struct squashfs_lz4 *stream = strm;
+
+	if (stream) {
+		vfree(stream->input);
+		vfree(stream->output);
+	}
+	kfree(stream);
+}
+
+
+static int lz4_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);
+	struct squashfs_lz4 *stream = strm;
+	void *buff = stream->input, *data;
+	int bytes = length, res;
+
+	while (bio_next_segment(bio, &iter_all)) {
+		int avail = min(bytes, ((int)bvec->bv_len) - offset);
+
+		data = bvec_virt(bvec);
+		memcpy(buff, data + offset, avail);
+		buff += avail;
+		bytes -= avail;
+		offset = 0;
+	}
+
+	res = LZ4_decompress_safe(stream->input, stream->output,
+		length, output->length);
+
+	if (res < 0)
+		return -EIO;
+
+	bytes = res;
+	data = squashfs_first_page(output);
+	buff = stream->output;
+	while (data) {
+		if (bytes <= PAGE_SIZE) {
+			if (!IS_ERR(data))
+				memcpy(data, buff, bytes);
+			break;
+		}
+		if (!IS_ERR(data))
+			memcpy(data, buff, PAGE_SIZE);
+		buff += PAGE_SIZE;
+		bytes -= PAGE_SIZE;
+		data = squashfs_next_page(output);
+	}
+	squashfs_finish_page(output);
+
+	return res;
+}
+
+const struct squashfs_decompressor squashfs_lz4_comp_ops = {
+	.init = lz4_init,
+	.comp_opts = lz4_comp_opts,
+	.free = lz4_free,
+	.decompress = lz4_uncompress,
+	.id = LZ4_COMPRESSION,
+	.name = "lz4",
+	.alloc_buffer = 0,
+	.supported = 1
+};