ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 90 insertions, 0 deletions

diff --git a/net/ipv6/ip6_checksum.c b/net/ipv6/ip6_checksum.c
new file mode 100644
index 000000000..e1a594873
--- /dev/null
+++ b/net/ipv6/ip6_checksum.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <net/ip.h>
+#include <net/ip6_checksum.h>
+#include <net/udp.h>
+#include <asm/checksum.h>
+
+#ifndef _HAVE_ARCH_IPV6_CSUM
+__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
+			const struct in6_addr *daddr,
+			__u32 len, __u8 proto, __wsum csum)
+{
+
+	int carry;
+	__u32 ulen;
+	__u32 uproto;
+	__u32 sum = (__force u32)csum;
+
+	sum += (__force u32)saddr->s6_addr32[0];
+	carry = (sum < (__force u32)saddr->s6_addr32[0]);
+	sum += carry;
+
+	sum += (__force u32)saddr->s6_addr32[1];
+	carry = (sum < (__force u32)saddr->s6_addr32[1]);
+	sum += carry;
+
+	sum += (__force u32)saddr->s6_addr32[2];
+	carry = (sum < (__force u32)saddr->s6_addr32[2]);
+	sum += carry;
+
+	sum += (__force u32)saddr->s6_addr32[3];
+	carry = (sum < (__force u32)saddr->s6_addr32[3]);
+	sum += carry;
+
+	sum += (__force u32)daddr->s6_addr32[0];
+	carry = (sum < (__force u32)daddr->s6_addr32[0]);
+	sum += carry;
+
+	sum += (__force u32)daddr->s6_addr32[1];
+	carry = (sum < (__force u32)daddr->s6_addr32[1]);
+	sum += carry;
+
+	sum += (__force u32)daddr->s6_addr32[2];
+	carry = (sum < (__force u32)daddr->s6_addr32[2]);
+	sum += carry;
+
+	sum += (__force u32)daddr->s6_addr32[3];
+	carry = (sum < (__force u32)daddr->s6_addr32[3]);
+	sum += carry;
+
+	ulen = (__force u32)htonl((__u32) len);
+	sum += ulen;
+	carry = (sum < ulen);
+	sum += carry;
+
+	uproto = (__force u32)htonl(proto);
+	sum += uproto;
+	carry = (sum < uproto);
+	sum += carry;
+
+	return csum_fold((__force __wsum)sum);
+}
+EXPORT_SYMBOL(csum_ipv6_magic);
+#endif
+
+/* Function to set UDP checksum for an IPv6 UDP packet. This is intended
+ * for the simple case like when setting the checksum for a UDP tunnel.
+ */
+void udp6_set_csum(bool nocheck, struct sk_buff *skb,
+		   const struct in6_addr *saddr,
+		   const struct in6_addr *daddr, int len)
+{
+	struct udphdr *uh = udp_hdr(skb);
+
+	if (nocheck)
+		uh->check = 0;
+	else if (skb_is_gso(skb))
+		uh->check = ~udp_v6_check(len, saddr, daddr, 0);
+	else if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		uh->check = 0;
+		uh->check = udp_v6_check(len, saddr, daddr, lco_csum(skb));
+		if (uh->check == 0)
+			uh->check = CSUM_MANGLED_0;
+	} else {
+		skb->ip_summed = CHECKSUM_PARTIAL;
+		skb->csum_start = skb_transport_header(skb) - skb->head;
+		skb->csum_offset = offsetof(struct udphdr, check);
+		uh->check = ~udp_v6_check(len, saddr, daddr, 0);
+	}
+}
+EXPORT_SYMBOL(udp6_set_csum);