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, 92 insertions, 0 deletions

diff --git a/scripts/syscalltbl.sh b/scripts/syscalltbl.sh
new file mode 100755
index 000000000..6a903b87a
--- /dev/null
+++ b/scripts/syscalltbl.sh
@@ -0,0 +1,92 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Generate a syscall table header.
+#
+# Each line of the syscall table should have the following format:
+#
+# NR ABI NAME [NATIVE] [COMPAT]
+#
+# NR       syscall number
+# ABI      ABI name
+# NAME     syscall name
+# NATIVE   native entry point (optional)
+# COMPAT   compat entry point (optional)
+
+set -e
+
+usage() {
+	echo >&2 "usage: $0 [--abis ABIS] INFILE OUTFILE" >&2
+	echo >&2
+	echo >&2 "  INFILE    input syscall table"
+	echo >&2 "  OUTFILE   output header file"
+	echo >&2
+	echo >&2 "options:"
+	echo >&2 "  --abis ABIS        ABI(s) to handle (By default, all lines are handled)"
+	exit 1
+}
+
+# default unless specified by options
+abis=
+
+while [ $# -gt 0 ]
+do
+	case $1 in
+	--abis)
+		abis=$(echo "($2)" | tr ',' '|')
+		shift 2;;
+	-*)
+		echo "$1: unknown option" >&2
+		usage;;
+	*)
+		break;;
+	esac
+done
+
+if [ $# -ne 2 ]; then
+	usage
+fi
+
+infile="$1"
+outfile="$2"
+
+nxt=0
+
+grep -E "^[0-9]+[[:space:]]+$abis" "$infile" | {
+
+	while read nr abi name native compat noreturn; do
+
+		if [ $nxt -gt $nr ]; then
+			echo "error: $infile: syscall table is not sorted or duplicates the same syscall number" >&2
+			exit 1
+		fi
+
+		while [ $nxt -lt $nr ]; do
+			echo "__SYSCALL($nxt, sys_ni_syscall)"
+			nxt=$((nxt + 1))
+		done
+
+		if [ "$compat" = "-" ]; then
+			unset compat
+		fi
+
+		if [ -n "$noreturn" ]; then
+			if [ "$noreturn" != "noreturn" ]; then
+				echo "error: $infile: invalid string \"$noreturn\" in 'noreturn' column"
+				exit 1
+			fi
+			if [ -n "$compat" ]; then
+				echo "__SYSCALL_COMPAT_NORETURN($nr, $native, $compat)"
+			else
+				echo "__SYSCALL_NORETURN($nr, $native)"
+			fi
+		elif [ -n "$compat" ]; then
+			echo "__SYSCALL_WITH_COMPAT($nr, $native, $compat)"
+		elif [ -n "$native" ]; then
+			echo "__SYSCALL($nr, $native)"
+		else
+			echo "__SYSCALL($nr, sys_ni_syscall)"
+		fi
+		nxt=$((nr + 1))
+	done
+} > "$outfile"