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, 103 insertions, 0 deletions

diff --git a/crypto/proc.c b/crypto/proc.c
new file mode 100644
index 000000000..5fb9fe86d
--- /dev/null
+++ b/crypto/proc.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Scatterlist Cryptographic API.
+ *
+ * Procfs information.
+ *
+ * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
+ * Copyright (c) 2005 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <linux/atomic.h>
+#include <linux/init.h>
+#include <linux/crypto.h>
+#include <linux/fips.h>
+#include <linux/module.h>	/* for module_name() */
+#include <linux/rwsem.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+	__acquires_shared(&crypto_alg_sem)
+{
+	down_read(&crypto_alg_sem);
+	return seq_list_start(&crypto_alg_list, *pos);
+}
+
+static void *c_next(struct seq_file *m, void *p, loff_t *pos)
+	__must_hold_shared(&crypto_alg_sem)
+{
+	return seq_list_next(p, &crypto_alg_list, pos);
+}
+
+static void c_stop(struct seq_file *m, void *p)
+	__releases_shared(&crypto_alg_sem)
+{
+	up_read(&crypto_alg_sem);
+}
+
+static int c_show(struct seq_file *m, void *p)
+{
+	struct crypto_alg *alg = list_entry(p, struct crypto_alg, cra_list);
+
+	seq_printf(m, "name         : %s\n", alg->cra_name);
+	seq_printf(m, "driver       : %s\n", alg->cra_driver_name);
+	seq_printf(m, "module       : %s\n", module_name(alg->cra_module));
+	seq_printf(m, "priority     : %d\n", alg->cra_priority);
+	seq_printf(m, "refcnt       : %u\n", refcount_read(&alg->cra_refcnt));
+	seq_printf(m, "selftest     : %s\n",
+		   (alg->cra_flags & CRYPTO_ALG_TESTED) ?
+		   "passed" : "unknown");
+	seq_printf(m, "internal     : %s\n",
+		   str_yes_no(alg->cra_flags & CRYPTO_ALG_INTERNAL));
+	if (fips_enabled)
+		seq_printf(m, "fips         : %s\n",
+			str_no_yes(alg->cra_flags & CRYPTO_ALG_FIPS_INTERNAL));
+
+	if (alg->cra_flags & CRYPTO_ALG_LARVAL) {
+		seq_printf(m, "type         : larval\n");
+		seq_printf(m, "flags        : 0x%x\n", alg->cra_flags);
+		goto out;
+	}
+
+	if (alg->cra_type && alg->cra_type->show) {
+		alg->cra_type->show(m, alg);
+		goto out;
+	}
+
+	switch (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) {
+	case CRYPTO_ALG_TYPE_CIPHER:
+		seq_printf(m, "type         : cipher\n");
+		seq_printf(m, "blocksize    : %u\n", alg->cra_blocksize);
+		seq_printf(m, "min keysize  : %u\n",
+					alg->cra_cipher.cia_min_keysize);
+		seq_printf(m, "max keysize  : %u\n",
+					alg->cra_cipher.cia_max_keysize);
+		break;
+	default:
+		seq_printf(m, "type         : unknown\n");
+		break;
+	}
+
+out:
+	seq_putc(m, '\n');
+	return 0;
+}
+
+static const struct seq_operations crypto_seq_ops = {
+	.start		= c_start,
+	.next		= c_next,
+	.stop		= c_stop,
+	.show		= c_show
+};
+
+void __init crypto_init_proc(void)
+{
+	proc_create_seq("crypto", 0, NULL, &crypto_seq_ops);
+}
+
+void __exit crypto_exit_proc(void)
+{
+	remove_proc_entry("crypto", NULL);
+}