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, 96 insertions, 0 deletions

diff --git a/net/batman-adv/bitarray.c b/net/batman-adv/bitarray.c
new file mode 100644
index 000000000..f814756d9
--- /dev/null
+++ b/net/batman-adv/bitarray.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) B.A.T.M.A.N. contributors:
+ *
+ * Simon Wunderlich, Marek Lindner
+ */
+
+#include "bitarray.h"
+#include "main.h"
+
+#include <linux/bitmap.h>
+
+#include "log.h"
+
+/**
+ * batadv_bitmap_shift_left() - shift the sequence number bitmap left
+ * @seq_bits: the sequence number bitmap to shift
+ * @n: number of positions to shift left
+ *
+ * Shift @seq_bits by @n positions. No-op if @n is not within the bounds of
+ * the bitmap.
+ */
+static void batadv_bitmap_shift_left(unsigned long *seq_bits, s32 n)
+{
+	if (n <= 0 || n >= BATADV_TQ_LOCAL_WINDOW_SIZE)
+		return;
+
+	bitmap_shift_left(seq_bits, seq_bits, n, BATADV_TQ_LOCAL_WINDOW_SIZE);
+}
+
+/**
+ * batadv_bit_get_packet() - receive and process one packet within the sequence
+ *  number window
+ * @priv: the bat priv with all the mesh interface information
+ * @seq_bits: pointer to the sequence number bitmap of received packets
+ * @seq_num_diff: difference between the current/received sequence number and
+ *  the last sequence number
+ * @set_mark: whether this packet should be marked in seq_bits
+ *
+ * Return: true if the window was moved (either new or very old),
+ *  false if the window was not moved/shifted.
+ */
+bool batadv_bit_get_packet(void *priv, unsigned long *seq_bits,
+			   s32 seq_num_diff, int set_mark)
+{
+	struct batadv_priv *bat_priv = priv;
+
+	/* sequence number is slightly older. We already got a sequence number
+	 * higher than this one, so we just mark it.
+	 */
+	if (seq_num_diff <= 0 && seq_num_diff > -BATADV_TQ_LOCAL_WINDOW_SIZE) {
+		if (set_mark)
+			batadv_set_bit(seq_bits, -seq_num_diff);
+		return false;
+	}
+
+	/* sequence number is slightly newer, so we shift the window and
+	 * set the mark if required
+	 */
+	if (seq_num_diff > 0 && seq_num_diff < BATADV_TQ_LOCAL_WINDOW_SIZE) {
+		batadv_bitmap_shift_left(seq_bits, seq_num_diff);
+
+		if (set_mark)
+			batadv_set_bit(seq_bits, 0);
+		return true;
+	}
+
+	/* sequence number is much newer, probably missed a lot of packets */
+	if (seq_num_diff >= BATADV_TQ_LOCAL_WINDOW_SIZE &&
+	    seq_num_diff < BATADV_EXPECTED_SEQNO_RANGE) {
+		batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+			   "We missed a lot of packets (%i) !\n",
+			   seq_num_diff - 1);
+		bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
+		if (set_mark)
+			batadv_set_bit(seq_bits, 0);
+		return true;
+	}
+
+	/* received a much older packet. The other host either restarted
+	 * or the old packet got delayed somewhere in the network. The
+	 * packet should be dropped without calling this function if the
+	 * seqno window is protected.
+	 *
+	 * seq_num_diff <= -BATADV_TQ_LOCAL_WINDOW_SIZE
+	 * or
+	 * seq_num_diff >= BATADV_EXPECTED_SEQNO_RANGE
+	 */
+	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
+		   "Other host probably restarted!\n");
+
+	bitmap_zero(seq_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
+	if (set_mark)
+		batadv_set_bit(seq_bits, 0);
+
+	return true;
+}