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, 150 insertions, 0 deletions

diff --git a/samples/bpf/parse_varlen.c b/samples/bpf/parse_varlen.c
new file mode 100644
index 000000000..d8623846e
--- /dev/null
+++ b/samples/bpf/parse_varlen.c
@@ -0,0 +1,150 @@
+/* Copyright (c) 2016 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#define KBUILD_MODNAME "foo"
+#include <linux/if_ether.h>
+#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/in.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <uapi/linux/bpf.h>
+#include <net/ip.h>
+#include <bpf/bpf_helpers.h>
+
+#define DEFAULT_PKTGEN_UDP_PORT 9
+#define DEBUG 0
+
+static int tcp(void *data, uint64_t tp_off, void *data_end)
+{
+	struct tcphdr *tcp = data + tp_off;
+
+	if (tcp + 1 > data_end)
+		return 0;
+	if (tcp->dest == htons(80) || tcp->source == htons(80))
+		return TC_ACT_SHOT;
+	return 0;
+}
+
+static int udp(void *data, uint64_t tp_off, void *data_end)
+{
+	struct udphdr *udp = data + tp_off;
+
+	if (udp + 1 > data_end)
+		return 0;
+	if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT) ||
+	    udp->source == htons(DEFAULT_PKTGEN_UDP_PORT)) {
+		if (DEBUG) {
+			char fmt[] = "udp port 9 indeed\n";
+
+			bpf_trace_printk(fmt, sizeof(fmt));
+		}
+		return TC_ACT_SHOT;
+	}
+	return 0;
+}
+
+static int parse_ipv4(void *data, uint64_t nh_off, void *data_end)
+{
+	struct iphdr *iph;
+	uint64_t ihl_len;
+
+	iph = data + nh_off;
+	if (iph + 1 > data_end)
+		return 0;
+
+	if (ip_is_fragment(iph))
+		return 0;
+	ihl_len = iph->ihl * 4;
+
+	if (iph->protocol == IPPROTO_IPIP) {
+		iph = data + nh_off + ihl_len;
+		if (iph + 1 > data_end)
+			return 0;
+		ihl_len += iph->ihl * 4;
+	}
+
+	if (iph->protocol == IPPROTO_TCP)
+		return tcp(data, nh_off + ihl_len, data_end);
+	else if (iph->protocol == IPPROTO_UDP)
+		return udp(data, nh_off + ihl_len, data_end);
+	return 0;
+}
+
+static int parse_ipv6(void *data, uint64_t nh_off, void *data_end)
+{
+	struct ipv6hdr *ip6h;
+	struct iphdr *iph;
+	uint64_t ihl_len = sizeof(struct ipv6hdr);
+	uint64_t nexthdr;
+
+	ip6h = data + nh_off;
+	if (ip6h + 1 > data_end)
+		return 0;
+
+	nexthdr = ip6h->nexthdr;
+
+	if (nexthdr == IPPROTO_IPIP) {
+		iph = data + nh_off + ihl_len;
+		if (iph + 1 > data_end)
+			return 0;
+		ihl_len += iph->ihl * 4;
+		nexthdr = iph->protocol;
+	} else if (nexthdr == IPPROTO_IPV6) {
+		ip6h = data + nh_off + ihl_len;
+		if (ip6h + 1 > data_end)
+			return 0;
+		ihl_len += sizeof(struct ipv6hdr);
+		nexthdr = ip6h->nexthdr;
+	}
+
+	if (nexthdr == IPPROTO_TCP)
+		return tcp(data, nh_off + ihl_len, data_end);
+	else if (nexthdr == IPPROTO_UDP)
+		return udp(data, nh_off + ihl_len, data_end);
+	return 0;
+}
+
+SEC("varlen")
+int handle_ingress(struct __sk_buff *skb)
+{
+	void *data = (void *)(long)skb->data;
+	struct ethhdr *eth = data;
+	void *data_end = (void *)(long)skb->data_end;
+	uint64_t h_proto, nh_off;
+
+	nh_off = sizeof(*eth);
+	if (data + nh_off > data_end)
+		return 0;
+
+	h_proto = eth->h_proto;
+
+	if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
+		struct vlan_hdr *vhdr;
+
+		vhdr = data + nh_off;
+		nh_off += sizeof(struct vlan_hdr);
+		if (data + nh_off > data_end)
+			return 0;
+		h_proto = vhdr->h_vlan_encapsulated_proto;
+	}
+	if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
+		struct vlan_hdr *vhdr;
+
+		vhdr = data + nh_off;
+		nh_off += sizeof(struct vlan_hdr);
+		if (data + nh_off > data_end)
+			return 0;
+		h_proto = vhdr->h_vlan_encapsulated_proto;
+	}
+	if (h_proto == htons(ETH_P_IP))
+		return parse_ipv4(data, nh_off, data_end);
+	else if (h_proto == htons(ETH_P_IPV6))
+		return parse_ipv6(data, nh_off, data_end);
+	return 0;
+}
+char _license[] SEC("license") = "GPL";