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, 70 insertions, 0 deletions

diff --git a/lib/crypto/chacha.c b/lib/crypto/chacha.c
new file mode 100644
index 000000000..86e5d382a
--- /dev/null
+++ b/lib/crypto/chacha.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The ChaCha stream cipher (RFC7539)
+ *
+ * Copyright (C) 2015 Martin Willi
+ */
+
+#include <crypto/chacha.h>
+#include <crypto/utils.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+static void __maybe_unused
+chacha_crypt_generic(struct chacha_state *state, u8 *dst, const u8 *src,
+		     unsigned int bytes, int nrounds)
+{
+	/* aligned to potentially speed up crypto_xor() */
+	u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
+
+	while (bytes >= CHACHA_BLOCK_SIZE) {
+		chacha_block_generic(state, stream, nrounds);
+		crypto_xor_cpy(dst, src, stream, CHACHA_BLOCK_SIZE);
+		bytes -= CHACHA_BLOCK_SIZE;
+		dst += CHACHA_BLOCK_SIZE;
+		src += CHACHA_BLOCK_SIZE;
+	}
+	if (bytes) {
+		chacha_block_generic(state, stream, nrounds);
+		crypto_xor_cpy(dst, src, stream, bytes);
+	}
+}
+
+#ifdef CONFIG_CRYPTO_LIB_CHACHA_ARCH
+#include "chacha.h" /* $(SRCARCH)/chacha.h */
+#else
+#define chacha_crypt_arch chacha_crypt_generic
+#define hchacha_block_arch hchacha_block_generic
+#endif
+
+void chacha_crypt(struct chacha_state *state, u8 *dst, const u8 *src,
+		  unsigned int bytes, int nrounds)
+{
+	chacha_crypt_arch(state, dst, src, bytes, nrounds);
+}
+EXPORT_SYMBOL_GPL(chacha_crypt);
+
+void hchacha_block(const struct chacha_state *state,
+		   u32 out[HCHACHA_OUT_WORDS], int nrounds)
+{
+	hchacha_block_arch(state, out, nrounds);
+}
+EXPORT_SYMBOL_GPL(hchacha_block);
+
+#ifdef chacha_mod_init_arch
+static int __init chacha_mod_init(void)
+{
+	chacha_mod_init_arch();
+	return 0;
+}
+subsys_initcall(chacha_mod_init);
+
+static void __exit chacha_mod_exit(void)
+{
+}
+module_exit(chacha_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("ChaCha stream cipher (RFC7539)");
+MODULE_LICENSE("GPL");