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, 73 insertions, 0 deletions

diff --git a/lib/crc/crc7.c b/lib/crc/crc7.c
new file mode 100644
index 000000000..46b95d7ac
--- /dev/null
+++ b/lib/crc/crc7.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *      crc7.c
+ */
+
+#include <linux/crc7.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+/*
+ * Table for CRC-7 (polynomial x^7 + x^3 + 1).
+ * This is a big-endian CRC (msbit is highest power of x),
+ * aligned so the msbit of the byte is the x^6 coefficient
+ * and the lsbit is not used.
+ */
+static const u8 crc7_be_syndrome_table[256] = {
+	0x00, 0x12, 0x24, 0x36, 0x48, 0x5a, 0x6c, 0x7e,
+	0x90, 0x82, 0xb4, 0xa6, 0xd8, 0xca, 0xfc, 0xee,
+	0x32, 0x20, 0x16, 0x04, 0x7a, 0x68, 0x5e, 0x4c,
+	0xa2, 0xb0, 0x86, 0x94, 0xea, 0xf8, 0xce, 0xdc,
+	0x64, 0x76, 0x40, 0x52, 0x2c, 0x3e, 0x08, 0x1a,
+	0xf4, 0xe6, 0xd0, 0xc2, 0xbc, 0xae, 0x98, 0x8a,
+	0x56, 0x44, 0x72, 0x60, 0x1e, 0x0c, 0x3a, 0x28,
+	0xc6, 0xd4, 0xe2, 0xf0, 0x8e, 0x9c, 0xaa, 0xb8,
+	0xc8, 0xda, 0xec, 0xfe, 0x80, 0x92, 0xa4, 0xb6,
+	0x58, 0x4a, 0x7c, 0x6e, 0x10, 0x02, 0x34, 0x26,
+	0xfa, 0xe8, 0xde, 0xcc, 0xb2, 0xa0, 0x96, 0x84,
+	0x6a, 0x78, 0x4e, 0x5c, 0x22, 0x30, 0x06, 0x14,
+	0xac, 0xbe, 0x88, 0x9a, 0xe4, 0xf6, 0xc0, 0xd2,
+	0x3c, 0x2e, 0x18, 0x0a, 0x74, 0x66, 0x50, 0x42,
+	0x9e, 0x8c, 0xba, 0xa8, 0xd6, 0xc4, 0xf2, 0xe0,
+	0x0e, 0x1c, 0x2a, 0x38, 0x46, 0x54, 0x62, 0x70,
+	0x82, 0x90, 0xa6, 0xb4, 0xca, 0xd8, 0xee, 0xfc,
+	0x12, 0x00, 0x36, 0x24, 0x5a, 0x48, 0x7e, 0x6c,
+	0xb0, 0xa2, 0x94, 0x86, 0xf8, 0xea, 0xdc, 0xce,
+	0x20, 0x32, 0x04, 0x16, 0x68, 0x7a, 0x4c, 0x5e,
+	0xe6, 0xf4, 0xc2, 0xd0, 0xae, 0xbc, 0x8a, 0x98,
+	0x76, 0x64, 0x52, 0x40, 0x3e, 0x2c, 0x1a, 0x08,
+	0xd4, 0xc6, 0xf0, 0xe2, 0x9c, 0x8e, 0xb8, 0xaa,
+	0x44, 0x56, 0x60, 0x72, 0x0c, 0x1e, 0x28, 0x3a,
+	0x4a, 0x58, 0x6e, 0x7c, 0x02, 0x10, 0x26, 0x34,
+	0xda, 0xc8, 0xfe, 0xec, 0x92, 0x80, 0xb6, 0xa4,
+	0x78, 0x6a, 0x5c, 0x4e, 0x30, 0x22, 0x14, 0x06,
+	0xe8, 0xfa, 0xcc, 0xde, 0xa0, 0xb2, 0x84, 0x96,
+	0x2e, 0x3c, 0x0a, 0x18, 0x66, 0x74, 0x42, 0x50,
+	0xbe, 0xac, 0x9a, 0x88, 0xf6, 0xe4, 0xd2, 0xc0,
+	0x1c, 0x0e, 0x38, 0x2a, 0x54, 0x46, 0x70, 0x62,
+	0x8c, 0x9e, 0xa8, 0xba, 0xc4, 0xd6, 0xe0, 0xf2
+};
+
+/**
+ * crc7_be - update the CRC7 for the data buffer
+ * @crc:     previous CRC7 value
+ * @buffer:  data pointer
+ * @len:     number of bytes in the buffer
+ * Context: any
+ *
+ * Returns the updated CRC7 value.
+ * The CRC7 is left-aligned in the byte (the lsbit is always 0), as that
+ * makes the computation easier, and all callers want it in that form.
+ *
+ */
+u8 crc7_be(u8 crc, const u8 *buffer, size_t len)
+{
+	while (len--)
+		crc = crc7_be_syndrome_table[crc ^ *buffer++];
+	return crc;
+}
+EXPORT_SYMBOL(crc7_be);
+
+MODULE_DESCRIPTION("CRC7 calculations");
+MODULE_LICENSE("GPL");