x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 179 insertions, 0 deletions

diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c
new file mode 100644
index 000000000..ad57c4c9e
--- /dev/null
+++ b/net/ipv4/udp_bpf.c
@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Cloudflare Ltd https://cloudflare.com */
+
+#include <linux/skmsg.h>
+#include <net/sock.h>
+#include <net/udp.h>
+#include <net/inet_common.h>
+#include <asm/ioctls.h>
+
+static struct proto *udpv6_prot_saved __read_mostly;
+
+static int sk_udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
+			  int flags)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6)
+		return udpv6_prot_saved->recvmsg(sk, msg, len, flags);
+#endif
+	return udp_prot.recvmsg(sk, msg, len, flags);
+}
+
+static bool udp_sk_has_data(struct sock *sk)
+{
+	return !skb_queue_empty(&udp_sk(sk)->reader_queue) ||
+	       !skb_queue_empty(&sk->sk_receive_queue);
+}
+
+static bool psock_has_data(struct sk_psock *psock)
+{
+	return !skb_queue_empty(&psock->ingress_skb) ||
+	       !sk_psock_queue_empty(psock);
+}
+
+#define udp_msg_has_data(__sk, __psock)	\
+		({ udp_sk_has_data(__sk) || psock_has_data(__psock); })
+
+static int udp_msg_wait_data(struct sock *sk, struct sk_psock *psock,
+			     long timeo)
+{
+	DEFINE_WAIT_FUNC(wait, woken_wake_function);
+	int ret = 0;
+
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		return 1;
+
+	if (!timeo)
+		return ret;
+
+	add_wait_queue(sk_sleep(sk), &wait);
+	sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+	ret = udp_msg_has_data(sk, psock);
+	if (!ret) {
+		release_sock(sk);
+		wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
+		lock_sock(sk);
+		ret = udp_msg_has_data(sk, psock);
+	}
+	sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
+	remove_wait_queue(sk_sleep(sk), &wait);
+	return ret;
+}
+
+static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
+			   int flags)
+{
+	struct sk_psock *psock;
+	int copied, ret;
+
+	if (unlikely(flags & MSG_ERRQUEUE))
+		return inet_recv_error(sk, msg, len);
+
+	if (!len)
+		return 0;
+
+	psock = sk_psock_get(sk);
+	if (unlikely(!psock))
+		return sk_udp_recvmsg(sk, msg, len, flags);
+
+	if (!psock_has_data(psock)) {
+		ret = sk_udp_recvmsg(sk, msg, len, flags);
+		goto out;
+	}
+
+	lock_sock(sk);
+msg_bytes_ready:
+	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
+	if (!copied) {
+		long timeo;
+		int data;
+
+		timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
+		data = udp_msg_wait_data(sk, psock, timeo);
+		if (data) {
+			if (psock_has_data(psock))
+				goto msg_bytes_ready;
+
+			release_sock(sk);
+
+			ret = sk_udp_recvmsg(sk, msg, len, flags);
+			goto out;
+		}
+		copied = -EAGAIN;
+	}
+
+	release_sock(sk);
+
+	ret = copied;
+out:
+	sk_psock_put(sk, psock);
+	return ret;
+}
+
+enum {
+	UDP_BPF_IPV4,
+	UDP_BPF_IPV6,
+	UDP_BPF_NUM_PROTS,
+};
+
+static DEFINE_SPINLOCK(udpv6_prot_lock);
+static struct proto udp_bpf_prots[UDP_BPF_NUM_PROTS];
+
+static int udp_bpf_ioctl(struct sock *sk, int cmd, int *karg)
+{
+	if (cmd != SIOCINQ)
+		return udp_ioctl(sk, cmd, karg);
+
+	/* Since we don't hold a lock, sk_receive_queue may contain data.
+	 * BPF might only be processing this data at the moment. We only
+	 * care about the data in the ingress_msg here.
+	 */
+	*karg = sk_msg_first_len(sk);
+	return 0;
+}
+
+static void udp_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
+{
+	*prot			= *base;
+	prot->close		= sock_map_close;
+	prot->recvmsg		= udp_bpf_recvmsg;
+	prot->sock_is_readable	= sk_msg_is_readable;
+	prot->ioctl		= udp_bpf_ioctl;
+}
+
+static void udp_bpf_check_v6_needs_rebuild(struct proto *ops)
+{
+	if (unlikely(ops != smp_load_acquire(&udpv6_prot_saved))) {
+		spin_lock_bh(&udpv6_prot_lock);
+		if (likely(ops != udpv6_prot_saved)) {
+			udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV6], ops);
+			smp_store_release(&udpv6_prot_saved, ops);
+		}
+		spin_unlock_bh(&udpv6_prot_lock);
+	}
+}
+
+static int __init udp_bpf_v4_build_proto(void)
+{
+	udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV4], &udp_prot);
+	return 0;
+}
+late_initcall(udp_bpf_v4_build_proto);
+
+int udp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
+{
+	int family = sk->sk_family == AF_INET ? UDP_BPF_IPV4 : UDP_BPF_IPV6;
+
+	if (restore) {
+		WRITE_ONCE(sk->sk_write_space, psock->saved_write_space);
+		sock_replace_proto(sk, psock->sk_proto);
+		return 0;
+	}
+
+	if (sk->sk_family == AF_INET6)
+		udp_bpf_check_v6_needs_rebuild(psock->sk_proto);
+
+	sock_replace_proto(sk, &udp_bpf_prots[family]);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(udp_bpf_update_proto);