x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 314 insertions, 0 deletions

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
new file mode 100644
index 000000000..813013ca4
--- /dev/null
+++ b/net/ipv6/proc.c
@@ -0,0 +1,314 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		This file implements the various access functions for the
+ *		PROC file system.  This is very similar to the IPv4 version,
+ *		except it reports the sockets in the INET6 address family.
+ *
+ * Authors:	David S. Miller (davem@caip.rutgers.edu)
+ *		YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
+ */
+#include <linux/socket.h>
+#include <linux/net.h>
+#include <linux/ipv6.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/stddef.h>
+#include <linux/export.h>
+#include <net/net_namespace.h>
+#include <net/ip.h>
+#include <net/sock.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+#include <net/transp_v6.h>
+#include <net/ipv6.h>
+
+#define MAX4(a, b, c, d) \
+	MAX_T(u32, MAX_T(u32, a, b), MAX_T(u32, c, d))
+#define SNMP_MIB_MAX MAX4(UDP_MIB_MAX, TCP_MIB_MAX, \
+			IPSTATS_MIB_MAX, ICMP_MIB_MAX)
+
+static int sockstat6_seq_show(struct seq_file *seq, void *v)
+{
+	struct net *net = seq->private;
+
+	seq_printf(seq, "TCP6: inuse %d\n",
+		       sock_prot_inuse_get(net, &tcpv6_prot));
+	seq_printf(seq, "UDP6: inuse %d\n",
+		       sock_prot_inuse_get(net, &udpv6_prot));
+	seq_printf(seq, "RAW6: inuse %d\n",
+		       sock_prot_inuse_get(net, &rawv6_prot));
+	seq_printf(seq, "FRAG6: inuse %u memory %lu\n",
+		   atomic_read(&net->ipv6.fqdir->rhashtable.nelems),
+		   frag_mem_limit(net->ipv6.fqdir));
+	return 0;
+}
+
+static const struct snmp_mib snmp6_ipstats_list[] = {
+/* ipv6 mib according to RFC 2465 */
+	SNMP_MIB_ITEM("Ip6InReceives", IPSTATS_MIB_INPKTS),
+	SNMP_MIB_ITEM("Ip6InHdrErrors", IPSTATS_MIB_INHDRERRORS),
+	SNMP_MIB_ITEM("Ip6InTooBigErrors", IPSTATS_MIB_INTOOBIGERRORS),
+	SNMP_MIB_ITEM("Ip6InNoRoutes", IPSTATS_MIB_INNOROUTES),
+	SNMP_MIB_ITEM("Ip6InAddrErrors", IPSTATS_MIB_INADDRERRORS),
+	SNMP_MIB_ITEM("Ip6InUnknownProtos", IPSTATS_MIB_INUNKNOWNPROTOS),
+	SNMP_MIB_ITEM("Ip6InTruncatedPkts", IPSTATS_MIB_INTRUNCATEDPKTS),
+	SNMP_MIB_ITEM("Ip6InDiscards", IPSTATS_MIB_INDISCARDS),
+	SNMP_MIB_ITEM("Ip6InDelivers", IPSTATS_MIB_INDELIVERS),
+	SNMP_MIB_ITEM("Ip6OutForwDatagrams", IPSTATS_MIB_OUTFORWDATAGRAMS),
+	SNMP_MIB_ITEM("Ip6OutRequests", IPSTATS_MIB_OUTREQUESTS),
+	SNMP_MIB_ITEM("Ip6OutDiscards", IPSTATS_MIB_OUTDISCARDS),
+	SNMP_MIB_ITEM("Ip6OutNoRoutes", IPSTATS_MIB_OUTNOROUTES),
+	SNMP_MIB_ITEM("Ip6ReasmTimeout", IPSTATS_MIB_REASMTIMEOUT),
+	SNMP_MIB_ITEM("Ip6ReasmReqds", IPSTATS_MIB_REASMREQDS),
+	SNMP_MIB_ITEM("Ip6ReasmOKs", IPSTATS_MIB_REASMOKS),
+	SNMP_MIB_ITEM("Ip6ReasmFails", IPSTATS_MIB_REASMFAILS),
+	SNMP_MIB_ITEM("Ip6FragOKs", IPSTATS_MIB_FRAGOKS),
+	SNMP_MIB_ITEM("Ip6FragFails", IPSTATS_MIB_FRAGFAILS),
+	SNMP_MIB_ITEM("Ip6FragCreates", IPSTATS_MIB_FRAGCREATES),
+	SNMP_MIB_ITEM("Ip6InMcastPkts", IPSTATS_MIB_INMCASTPKTS),
+	SNMP_MIB_ITEM("Ip6OutMcastPkts", IPSTATS_MIB_OUTMCASTPKTS),
+	SNMP_MIB_ITEM("Ip6InOctets", IPSTATS_MIB_INOCTETS),
+	SNMP_MIB_ITEM("Ip6OutOctets", IPSTATS_MIB_OUTOCTETS),
+	SNMP_MIB_ITEM("Ip6InMcastOctets", IPSTATS_MIB_INMCASTOCTETS),
+	SNMP_MIB_ITEM("Ip6OutMcastOctets", IPSTATS_MIB_OUTMCASTOCTETS),
+	SNMP_MIB_ITEM("Ip6InBcastOctets", IPSTATS_MIB_INBCASTOCTETS),
+	SNMP_MIB_ITEM("Ip6OutBcastOctets", IPSTATS_MIB_OUTBCASTOCTETS),
+	/* IPSTATS_MIB_CSUMERRORS is not relevant in IPv6 (no checksum) */
+	SNMP_MIB_ITEM("Ip6InNoECTPkts", IPSTATS_MIB_NOECTPKTS),
+	SNMP_MIB_ITEM("Ip6InECT1Pkts", IPSTATS_MIB_ECT1PKTS),
+	SNMP_MIB_ITEM("Ip6InECT0Pkts", IPSTATS_MIB_ECT0PKTS),
+	SNMP_MIB_ITEM("Ip6InCEPkts", IPSTATS_MIB_CEPKTS),
+	SNMP_MIB_ITEM("Ip6OutTransmits", IPSTATS_MIB_OUTPKTS),
+};
+
+static const struct snmp_mib snmp6_icmp6_list[] = {
+/* icmpv6 mib according to RFC 2466 */
+	SNMP_MIB_ITEM("Icmp6InMsgs", ICMP6_MIB_INMSGS),
+	SNMP_MIB_ITEM("Icmp6InErrors", ICMP6_MIB_INERRORS),
+	SNMP_MIB_ITEM("Icmp6OutMsgs", ICMP6_MIB_OUTMSGS),
+	SNMP_MIB_ITEM("Icmp6OutErrors", ICMP6_MIB_OUTERRORS),
+	SNMP_MIB_ITEM("Icmp6InCsumErrors", ICMP6_MIB_CSUMERRORS),
+/* ICMP6_MIB_RATELIMITHOST needs to be last, see snmp6_dev_seq_show(). */
+	SNMP_MIB_ITEM("Icmp6OutRateLimitHost", ICMP6_MIB_RATELIMITHOST),
+};
+
+static const struct snmp_mib snmp6_udp6_list[] = {
+	SNMP_MIB_ITEM("Udp6InDatagrams", UDP_MIB_INDATAGRAMS),
+	SNMP_MIB_ITEM("Udp6NoPorts", UDP_MIB_NOPORTS),
+	SNMP_MIB_ITEM("Udp6InErrors", UDP_MIB_INERRORS),
+	SNMP_MIB_ITEM("Udp6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
+	SNMP_MIB_ITEM("Udp6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
+	SNMP_MIB_ITEM("Udp6SndbufErrors", UDP_MIB_SNDBUFERRORS),
+	SNMP_MIB_ITEM("Udp6InCsumErrors", UDP_MIB_CSUMERRORS),
+	SNMP_MIB_ITEM("Udp6IgnoredMulti", UDP_MIB_IGNOREDMULTI),
+	SNMP_MIB_ITEM("Udp6MemErrors", UDP_MIB_MEMERRORS),
+};
+
+static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, atomic_long_t *smib)
+{
+	char name[32];
+	int i;
+
+	/* print by name -- deprecated items */
+	for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
+		const char *p = NULL;
+		int icmptype;
+
+#define CASE(TYP, STR) case TYP: p = STR; break;
+
+		icmptype = i & 0xff;
+		switch (icmptype) {
+/* RFC 4293 v6 ICMPMsgStatsTable; named items for RFC 2466 compatibility */
+		CASE(ICMPV6_DEST_UNREACH,	"DestUnreachs")
+		CASE(ICMPV6_PKT_TOOBIG,		"PktTooBigs")
+		CASE(ICMPV6_TIME_EXCEED,	"TimeExcds")
+		CASE(ICMPV6_PARAMPROB,		"ParmProblems")
+		CASE(ICMPV6_ECHO_REQUEST,	"Echos")
+		CASE(ICMPV6_ECHO_REPLY,		"EchoReplies")
+		CASE(ICMPV6_MGM_QUERY,		"GroupMembQueries")
+		CASE(ICMPV6_MGM_REPORT,		"GroupMembResponses")
+		CASE(ICMPV6_MGM_REDUCTION,	"GroupMembReductions")
+		CASE(ICMPV6_MLD2_REPORT,	"MLDv2Reports")
+		CASE(NDISC_ROUTER_ADVERTISEMENT, "RouterAdvertisements")
+		CASE(NDISC_ROUTER_SOLICITATION, "RouterSolicits")
+		CASE(NDISC_NEIGHBOUR_ADVERTISEMENT, "NeighborAdvertisements")
+		CASE(NDISC_NEIGHBOUR_SOLICITATION, "NeighborSolicits")
+		CASE(NDISC_REDIRECT,		"Redirects")
+		}
+#undef CASE
+		if (!p)	/* don't print un-named types here */
+			continue;
+		snprintf(name, sizeof(name), "Icmp6%s%s",
+			i & 0x100 ? "Out" : "In", p);
+		seq_printf(seq, "%-32s\t%lu\n", name,
+			   atomic_long_read(smib + i));
+	}
+
+	/* print by number (nonzero only) - ICMPMsgStat format */
+	for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
+		unsigned long val;
+
+		val = atomic_long_read(smib + i);
+		if (!val)
+			continue;
+		snprintf(name, sizeof(name), "Icmp6%sType%u",
+			i & 0x100 ?  "Out" : "In", i & 0xff);
+		seq_printf(seq, "%-32s\t%lu\n", name, val);
+	}
+}
+
+/* can be called either with percpu mib (pcpumib != NULL),
+ * or shared one (smib != NULL)
+ */
+static void snmp6_seq_show_item(struct seq_file *seq, void __percpu *pcpumib,
+				atomic_long_t *smib,
+				const struct snmp_mib *itemlist,
+				int cnt)
+{
+	unsigned long buff[SNMP_MIB_MAX];
+	int i;
+
+	if (pcpumib) {
+		memset(buff, 0, sizeof(unsigned long) * cnt);
+
+		snmp_get_cpu_field_batch_cnt(buff, itemlist, cnt, pcpumib);
+		for (i = 0; i < cnt; i++)
+			seq_printf(seq, "%-32s\t%lu\n",
+				   itemlist[i].name, buff[i]);
+	} else {
+		for (i = 0; i < cnt; i++)
+			seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name,
+				   atomic_long_read(smib + itemlist[i].entry));
+	}
+}
+
+static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu *mib,
+				  const struct snmp_mib *itemlist,
+				  int cnt, size_t syncpoff)
+{
+	u64 buff64[SNMP_MIB_MAX];
+	int i;
+
+	memset(buff64, 0, sizeof(u64) * cnt);
+
+	snmp_get_cpu_field64_batch_cnt(buff64, itemlist, cnt, mib, syncpoff);
+	for (i = 0; i < cnt; i++)
+		seq_printf(seq, "%-32s\t%llu\n", itemlist[i].name, buff64[i]);
+}
+
+static int snmp6_seq_show(struct seq_file *seq, void *v)
+{
+	struct net *net = (struct net *)seq->private;
+
+	snmp6_seq_show_item64(seq, net->mib.ipv6_statistics,
+			      snmp6_ipstats_list,
+			      ARRAY_SIZE(snmp6_ipstats_list),
+			      offsetof(struct ipstats_mib, syncp));
+	snmp6_seq_show_item(seq, net->mib.icmpv6_statistics,
+			    NULL, snmp6_icmp6_list,
+			    ARRAY_SIZE(snmp6_icmp6_list));
+	snmp6_seq_show_icmpv6msg(seq, net->mib.icmpv6msg_statistics->mibs);
+	snmp6_seq_show_item(seq, net->mib.udp_stats_in6,
+			    NULL, snmp6_udp6_list,
+			    ARRAY_SIZE(snmp6_udp6_list));
+	return 0;
+}
+
+static int snmp6_dev_seq_show(struct seq_file *seq, void *v)
+{
+	struct inet6_dev *idev = (struct inet6_dev *)seq->private;
+
+	seq_printf(seq, "%-32s\t%u\n", "ifIndex", idev->dev->ifindex);
+	snmp6_seq_show_item64(seq, idev->stats.ipv6,
+			      snmp6_ipstats_list,
+			      ARRAY_SIZE(snmp6_ipstats_list),
+			      offsetof(struct ipstats_mib, syncp));
+
+	/* Per idev icmp stats do not have ICMP6_MIB_RATELIMITHOST */
+	snmp6_seq_show_item(seq, NULL, idev->stats.icmpv6dev->mibs,
+			    snmp6_icmp6_list, ARRAY_SIZE(snmp6_icmp6_list) - 1);
+
+	snmp6_seq_show_icmpv6msg(seq, idev->stats.icmpv6msgdev->mibs);
+	return 0;
+}
+
+int snmp6_register_dev(struct inet6_dev *idev)
+{
+	struct proc_dir_entry *p;
+	struct net *net;
+
+	if (!idev || !idev->dev)
+		return -EINVAL;
+
+	net = dev_net(idev->dev);
+	if (!net->mib.proc_net_devsnmp6)
+		return -ENOENT;
+
+	p = proc_create_single_data(idev->dev->name, 0444,
+			net->mib.proc_net_devsnmp6, snmp6_dev_seq_show, idev);
+	if (!p)
+		return -ENOMEM;
+
+	idev->stats.proc_dir_entry = p;
+	return 0;
+}
+
+int snmp6_unregister_dev(struct inet6_dev *idev)
+{
+	struct net *net = dev_net(idev->dev);
+	if (!net->mib.proc_net_devsnmp6)
+		return -ENOENT;
+	if (!idev->stats.proc_dir_entry)
+		return -EINVAL;
+	proc_remove(idev->stats.proc_dir_entry);
+	idev->stats.proc_dir_entry = NULL;
+	return 0;
+}
+
+static int __net_init ipv6_proc_init_net(struct net *net)
+{
+	if (!proc_create_net_single("sockstat6", 0444, net->proc_net,
+			sockstat6_seq_show, NULL))
+		return -ENOMEM;
+
+	if (!proc_create_net_single("snmp6", 0444, net->proc_net,
+			snmp6_seq_show, NULL))
+		goto proc_snmp6_fail;
+
+	net->mib.proc_net_devsnmp6 = proc_mkdir("dev_snmp6", net->proc_net);
+	if (!net->mib.proc_net_devsnmp6)
+		goto proc_dev_snmp6_fail;
+	return 0;
+
+proc_dev_snmp6_fail:
+	remove_proc_entry("snmp6", net->proc_net);
+proc_snmp6_fail:
+	remove_proc_entry("sockstat6", net->proc_net);
+	return -ENOMEM;
+}
+
+static void __net_exit ipv6_proc_exit_net(struct net *net)
+{
+	remove_proc_entry("sockstat6", net->proc_net);
+	remove_proc_entry("dev_snmp6", net->proc_net);
+	remove_proc_entry("snmp6", net->proc_net);
+}
+
+static struct pernet_operations ipv6_proc_ops = {
+	.init = ipv6_proc_init_net,
+	.exit = ipv6_proc_exit_net,
+};
+
+int __init ipv6_misc_proc_init(void)
+{
+	return register_pernet_subsys(&ipv6_proc_ops);
+}
+
+void ipv6_misc_proc_exit(void)
+{
+	unregister_pernet_subsys(&ipv6_proc_ops);
+}