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, 88 insertions, 0 deletions

diff --git a/fs/smb/smbdirect/debug.c b/fs/smb/smbdirect/debug.c
new file mode 100644
index 000000000..344584344
--- /dev/null
+++ b/fs/smb/smbdirect/debug.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) 2017, Microsoft Corporation.
+ *   Copyright (c) 2025, Stefan Metzmacher
+ */
+
+#include "internal.h"
+#include <linux/seq_file.h>
+
+void smbdirect_connection_legacy_debug_proc_show(struct smbdirect_socket *sc,
+						 unsigned int rdma_readwrite_threshold,
+						 struct seq_file *m)
+{
+	const struct smbdirect_socket_parameters *sp;
+
+	if (!sc)
+		return;
+	sp = &sc->parameters;
+
+	seq_puts(m, "\n");
+	seq_printf(m, "SMBDirect protocol version: 0x%x ",
+		   SMBDIRECT_V1);
+	seq_printf(m, "transport status: %s (%u)",
+		   smbdirect_socket_status_string(sc->status),
+		   sc->status);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Conn receive_credit_max: %u ",
+		   sp->recv_credit_max);
+	seq_printf(m, "send_credit_target: %u max_send_size: %u",
+		   sp->send_credit_target,
+		   sp->max_send_size);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Conn max_fragmented_recv_size: %u ",
+		   sp->max_fragmented_recv_size);
+	seq_printf(m, "max_fragmented_send_size: %u max_receive_size:%u",
+		   sp->max_fragmented_send_size,
+		   sp->max_recv_size);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Conn keep_alive_interval: %u ",
+		   sp->keepalive_interval_msec / 1000);
+	seq_printf(m, "max_readwrite_size: %u rdma_readwrite_threshold: %u",
+		   sp->max_read_write_size,
+		   rdma_readwrite_threshold);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Debug count_get_receive_buffer: %llu ",
+		   sc->statistics.get_receive_buffer);
+	seq_printf(m, "count_put_receive_buffer: %llu count_send_empty: %llu",
+		   sc->statistics.put_receive_buffer,
+		   sc->statistics.send_empty);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Read Queue count_enqueue_reassembly_queue: %llu ",
+		   sc->statistics.enqueue_reassembly_queue);
+	seq_printf(m, "count_dequeue_reassembly_queue: %llu ",
+		   sc->statistics.dequeue_reassembly_queue);
+	seq_printf(m, "reassembly_data_length: %u ",
+		   sc->recv_io.reassembly.data_length);
+	seq_printf(m, "reassembly_queue_length: %u",
+		   sc->recv_io.reassembly.queue_length);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Current Credits send_credits: %u ",
+		   atomic_read(&sc->send_io.credits.count));
+	seq_printf(m, "receive_credits: %u receive_credit_target: %u",
+		   atomic_read(&sc->recv_io.credits.count),
+		   sc->recv_io.credits.target);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "Pending send_pending: %u ",
+		   atomic_read(&sc->send_io.pending.count));
+
+	seq_puts(m, "\n");
+	seq_printf(m, "MR responder_resources: %u ",
+		   sp->responder_resources);
+	seq_printf(m, "max_frmr_depth: %u mr_type: 0x%x",
+		   sp->max_frmr_depth,
+		   sc->mr_io.type);
+
+	seq_puts(m, "\n");
+	seq_printf(m, "MR mr_ready_count: %u mr_used_count: %u",
+		   atomic_read(&sc->mr_io.ready.count),
+		   atomic_read(&sc->mr_io.used.count));
+}
+EXPORT_SYMBOL_GPL(smbdirect_connection_legacy_debug_proc_show);