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, 399 insertions, 0 deletions

diff --git a/net/sctp/proc.c b/net/sctp/proc.c
new file mode 100644
index 000000000..43433d7e2
--- /dev/null
+++ b/net/sctp/proc.c
@@ -0,0 +1,399 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* SCTP kernel implementation
+ * Copyright (c) 2003 International Business Machines, Corp.
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *    Sridhar Samudrala <sri@us.ibm.com>
+ */
+
+#include <linux/types.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <net/sctp/sctp.h>
+#include <net/ip.h> /* for snmp_fold_field */
+
+static const struct snmp_mib sctp_snmp_list[] = {
+	SNMP_MIB_ITEM("SctpCurrEstab", SCTP_MIB_CURRESTAB),
+	SNMP_MIB_ITEM("SctpActiveEstabs", SCTP_MIB_ACTIVEESTABS),
+	SNMP_MIB_ITEM("SctpPassiveEstabs", SCTP_MIB_PASSIVEESTABS),
+	SNMP_MIB_ITEM("SctpAborteds", SCTP_MIB_ABORTEDS),
+	SNMP_MIB_ITEM("SctpShutdowns", SCTP_MIB_SHUTDOWNS),
+	SNMP_MIB_ITEM("SctpOutOfBlues", SCTP_MIB_OUTOFBLUES),
+	SNMP_MIB_ITEM("SctpChecksumErrors", SCTP_MIB_CHECKSUMERRORS),
+	SNMP_MIB_ITEM("SctpOutCtrlChunks", SCTP_MIB_OUTCTRLCHUNKS),
+	SNMP_MIB_ITEM("SctpOutOrderChunks", SCTP_MIB_OUTORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpOutUnorderChunks", SCTP_MIB_OUTUNORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpInCtrlChunks", SCTP_MIB_INCTRLCHUNKS),
+	SNMP_MIB_ITEM("SctpInOrderChunks", SCTP_MIB_INORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpInUnorderChunks", SCTP_MIB_INUNORDERCHUNKS),
+	SNMP_MIB_ITEM("SctpFragUsrMsgs", SCTP_MIB_FRAGUSRMSGS),
+	SNMP_MIB_ITEM("SctpReasmUsrMsgs", SCTP_MIB_REASMUSRMSGS),
+	SNMP_MIB_ITEM("SctpOutSCTPPacks", SCTP_MIB_OUTSCTPPACKS),
+	SNMP_MIB_ITEM("SctpInSCTPPacks", SCTP_MIB_INSCTPPACKS),
+	SNMP_MIB_ITEM("SctpT1InitExpireds", SCTP_MIB_T1_INIT_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT1CookieExpireds", SCTP_MIB_T1_COOKIE_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT2ShutdownExpireds", SCTP_MIB_T2_SHUTDOWN_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT3RtxExpireds", SCTP_MIB_T3_RTX_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT4RtoExpireds", SCTP_MIB_T4_RTO_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT5ShutdownGuardExpireds", SCTP_MIB_T5_SHUTDOWN_GUARD_EXPIREDS),
+	SNMP_MIB_ITEM("SctpDelaySackExpireds", SCTP_MIB_DELAY_SACK_EXPIREDS),
+	SNMP_MIB_ITEM("SctpAutocloseExpireds", SCTP_MIB_AUTOCLOSE_EXPIREDS),
+	SNMP_MIB_ITEM("SctpT3Retransmits", SCTP_MIB_T3_RETRANSMITS),
+	SNMP_MIB_ITEM("SctpPmtudRetransmits", SCTP_MIB_PMTUD_RETRANSMITS),
+	SNMP_MIB_ITEM("SctpFastRetransmits", SCTP_MIB_FAST_RETRANSMITS),
+	SNMP_MIB_ITEM("SctpInPktSoftirq", SCTP_MIB_IN_PKT_SOFTIRQ),
+	SNMP_MIB_ITEM("SctpInPktBacklog", SCTP_MIB_IN_PKT_BACKLOG),
+	SNMP_MIB_ITEM("SctpInPktDiscards", SCTP_MIB_IN_PKT_DISCARDS),
+	SNMP_MIB_ITEM("SctpInDataChunkDiscards", SCTP_MIB_IN_DATA_CHUNK_DISCARDS),
+};
+
+/* Display sctp snmp mib statistics(/proc/net/sctp/snmp). */
+static int sctp_snmp_seq_show(struct seq_file *seq, void *v)
+{
+	unsigned long buff[ARRAY_SIZE(sctp_snmp_list)];
+	const int cnt = ARRAY_SIZE(sctp_snmp_list);
+	struct net *net = seq->private;
+	int i;
+
+	memset(buff, 0, sizeof(buff));
+
+	snmp_get_cpu_field_batch_cnt(buff, sctp_snmp_list, cnt,
+				     net->sctp.sctp_statistics);
+	for (i = 0; i < cnt; i++)
+		seq_printf(seq, "%-32s\t%ld\n", sctp_snmp_list[i].name,
+						buff[i]);
+
+	return 0;
+}
+
+/* Dump local addresses of an association/endpoint. */
+static void sctp_seq_dump_local_addrs(struct seq_file *seq, struct sctp_ep_common *epb)
+{
+	struct sctp_association *asoc;
+	struct sctp_sockaddr_entry *laddr;
+	struct sctp_transport *peer;
+	union sctp_addr *addr, *primary = NULL;
+	struct sctp_af *af;
+
+	if (epb->type == SCTP_EP_TYPE_ASSOCIATION) {
+		asoc = sctp_assoc(epb);
+
+		peer = asoc->peer.primary_path;
+		if (unlikely(peer == NULL)) {
+			WARN(1, "Association %p with NULL primary path!\n", asoc);
+			return;
+		}
+
+		primary = &peer->saddr;
+	}
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(laddr, &epb->bind_addr.address_list, list) {
+		if (!laddr->valid)
+			continue;
+
+		addr = &laddr->a;
+		af = sctp_get_af_specific(addr->sa.sa_family);
+		if (primary && af->cmp_addr(addr, primary)) {
+			seq_printf(seq, "*");
+		}
+		af->seq_dump_addr(seq, addr);
+	}
+	rcu_read_unlock();
+}
+
+/* Dump remote addresses of an association. */
+static void sctp_seq_dump_remote_addrs(struct seq_file *seq, struct sctp_association *assoc)
+{
+	struct sctp_transport *transport;
+	union sctp_addr *addr, *primary;
+	struct sctp_af *af;
+
+	primary = &assoc->peer.primary_addr;
+	list_for_each_entry_rcu(transport, &assoc->peer.transport_addr_list,
+			transports) {
+		addr = &transport->ipaddr;
+
+		af = sctp_get_af_specific(addr->sa.sa_family);
+		if (af->cmp_addr(addr, primary)) {
+			seq_printf(seq, "*");
+		}
+		af->seq_dump_addr(seq, addr);
+	}
+}
+
+static void *sctp_eps_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	if (*pos >= sctp_ep_hashsize)
+		return NULL;
+
+	if (*pos < 0)
+		*pos = 0;
+
+	if (*pos == 0)
+		seq_printf(seq, " ENDPT     SOCK   STY SST HBKT LPORT   UID INODE LADDRS\n");
+
+	return (void *)pos;
+}
+
+static void sctp_eps_seq_stop(struct seq_file *seq, void *v)
+{
+}
+
+
+static void *sctp_eps_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	if (++*pos >= sctp_ep_hashsize)
+		return NULL;
+
+	return pos;
+}
+
+
+/* Display sctp endpoints (/proc/net/sctp/eps). */
+static int sctp_eps_seq_show(struct seq_file *seq, void *v)
+{
+	struct sctp_hashbucket *head;
+	struct sctp_endpoint *ep;
+	struct sock *sk;
+	int    hash = *(loff_t *)v;
+
+	if (hash >= sctp_ep_hashsize)
+		return -ENOMEM;
+
+	head = &sctp_ep_hashtable[hash];
+	read_lock_bh(&head->lock);
+	sctp_for_each_hentry(ep, &head->chain) {
+		sk = ep->base.sk;
+		if (!net_eq(sock_net(sk), seq_file_net(seq)))
+			continue;
+		seq_printf(seq, "%8pK %8pK %-3d %-3d %-4d %-5d %5u %5llu ", ep, sk,
+			   sctp_sk(sk)->type, sk->sk_state, hash,
+			   ep->base.bind_addr.port,
+			   from_kuid_munged(seq_user_ns(seq), sk_uid(sk)),
+			   sock_i_ino(sk));
+
+		sctp_seq_dump_local_addrs(seq, &ep->base);
+		seq_printf(seq, "\n");
+	}
+	read_unlock_bh(&head->lock);
+
+	return 0;
+}
+
+static const struct seq_operations sctp_eps_ops = {
+	.start = sctp_eps_seq_start,
+	.next  = sctp_eps_seq_next,
+	.stop  = sctp_eps_seq_stop,
+	.show  = sctp_eps_seq_show,
+};
+
+struct sctp_ht_iter {
+	struct seq_net_private p;
+	struct rhashtable_iter hti;
+};
+
+static void *sctp_transport_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct sctp_ht_iter *iter = seq->private;
+
+	sctp_transport_walk_start(&iter->hti);
+
+	return sctp_transport_get_idx(seq_file_net(seq), &iter->hti, *pos);
+}
+
+static void sctp_transport_seq_stop(struct seq_file *seq, void *v)
+{
+	struct sctp_ht_iter *iter = seq->private;
+
+	if (v && v != SEQ_START_TOKEN) {
+		struct sctp_transport *transport = v;
+
+		sctp_transport_put(transport);
+	}
+
+	sctp_transport_walk_stop(&iter->hti);
+}
+
+static void *sctp_transport_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct sctp_ht_iter *iter = seq->private;
+
+	if (v && v != SEQ_START_TOKEN) {
+		struct sctp_transport *transport = v;
+
+		sctp_transport_put(transport);
+	}
+
+	++*pos;
+
+	return sctp_transport_get_next(seq_file_net(seq), &iter->hti);
+}
+
+/* Display sctp associations (/proc/net/sctp/assocs). */
+static int sctp_assocs_seq_show(struct seq_file *seq, void *v)
+{
+	struct sctp_transport *transport;
+	struct sctp_association *assoc;
+	struct sctp_ep_common *epb;
+	struct sock *sk;
+
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, " ASSOC     SOCK   STY SST ST HBKT "
+				"ASSOC-ID TX_QUEUE RX_QUEUE UID INODE LPORT "
+				"RPORT LADDRS <-> RADDRS "
+				"HBINT INS OUTS MAXRT T1X T2X RTXC "
+				"wmema wmemq sndbuf rcvbuf\n");
+		return 0;
+	}
+
+	transport = (struct sctp_transport *)v;
+	assoc = transport->asoc;
+	epb = &assoc->base;
+	sk = epb->sk;
+
+	seq_printf(seq,
+		   "%8pK %8pK %-3d %-3d %-2d %-4d "
+		   "%4d %8d %8d %7u %5llu %-5d %5d ",
+		   assoc, sk, sctp_sk(sk)->type, sk->sk_state,
+		   assoc->state, 0,
+		   assoc->assoc_id,
+		   assoc->sndbuf_used,
+		   atomic_read(&assoc->rmem_alloc),
+		   from_kuid_munged(seq_user_ns(seq), sk_uid(sk)),
+		   sock_i_ino(sk),
+		   epb->bind_addr.port,
+		   assoc->peer.port);
+	seq_printf(seq, " ");
+	sctp_seq_dump_local_addrs(seq, epb);
+	seq_printf(seq, "<-> ");
+	sctp_seq_dump_remote_addrs(seq, assoc);
+	seq_printf(seq, "\t%8lu %5d %5d %4d %4d %4d %8d "
+		   "%8d %8d %8d %8d",
+		assoc->hbinterval, assoc->stream.incnt,
+		assoc->stream.outcnt, assoc->max_retrans,
+		assoc->init_retries, assoc->shutdown_retries,
+		assoc->rtx_data_chunks,
+		refcount_read(&sk->sk_wmem_alloc),
+		READ_ONCE(sk->sk_wmem_queued),
+		sk->sk_sndbuf,
+		sk->sk_rcvbuf);
+	seq_printf(seq, "\n");
+
+	return 0;
+}
+
+static const struct seq_operations sctp_assoc_ops = {
+	.start = sctp_transport_seq_start,
+	.next  = sctp_transport_seq_next,
+	.stop  = sctp_transport_seq_stop,
+	.show  = sctp_assocs_seq_show,
+};
+
+static int sctp_remaddr_seq_show(struct seq_file *seq, void *v)
+{
+	struct sctp_association *assoc;
+	struct sctp_transport *transport, *tsp;
+
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, "ADDR ASSOC_ID HB_ACT RTO MAX_PATH_RTX "
+				"REM_ADDR_RTX START STATE\n");
+		return 0;
+	}
+
+	transport = (struct sctp_transport *)v;
+	assoc = transport->asoc;
+
+	list_for_each_entry_rcu(tsp, &assoc->peer.transport_addr_list,
+				transports) {
+		/*
+		 * The remote address (ADDR)
+		 */
+		tsp->af_specific->seq_dump_addr(seq, &tsp->ipaddr);
+		seq_printf(seq, " ");
+		/*
+		 * The association ID (ASSOC_ID)
+		 */
+		seq_printf(seq, "%d ", tsp->asoc->assoc_id);
+
+		/*
+		 * If the Heartbeat is active (HB_ACT)
+		 * Note: 1 = Active, 0 = Inactive
+		 */
+		seq_printf(seq, "%d ", timer_pending(&tsp->hb_timer));
+
+		/*
+		 * Retransmit time out (RTO)
+		 */
+		seq_printf(seq, "%lu ", tsp->rto);
+
+		/*
+		 * Maximum path retransmit count (PATH_MAX_RTX)
+		 */
+		seq_printf(seq, "%d ", tsp->pathmaxrxt);
+
+		/*
+		 * remote address retransmit count (REM_ADDR_RTX)
+		 * Note: We don't have a way to tally this at the moment
+		 * so lets just leave it as zero for the moment
+		 */
+		seq_puts(seq, "0 ");
+
+		/*
+		 * remote address start time (START).  This is also not
+		 * currently implemented, but we can record it with a
+		 * jiffies marker in a subsequent patch
+		 */
+		seq_puts(seq, "0 ");
+
+		/*
+		 * The current state of this destination. I.e.
+		 * SCTP_ACTIVE, SCTP_INACTIVE, ...
+		 */
+		seq_printf(seq, "%d", tsp->state);
+
+		seq_printf(seq, "\n");
+	}
+
+	return 0;
+}
+
+static const struct seq_operations sctp_remaddr_ops = {
+	.start = sctp_transport_seq_start,
+	.next  = sctp_transport_seq_next,
+	.stop  = sctp_transport_seq_stop,
+	.show  = sctp_remaddr_seq_show,
+};
+
+/* Set up the proc fs entry for the SCTP protocol. */
+int __net_init sctp_proc_init(struct net *net)
+{
+	net->sctp.proc_net_sctp = proc_net_mkdir(net, "sctp", net->proc_net);
+	if (!net->sctp.proc_net_sctp)
+		return -ENOMEM;
+	if (!proc_create_net_single("snmp", 0444, net->sctp.proc_net_sctp,
+			 sctp_snmp_seq_show, NULL))
+		goto cleanup;
+	if (!proc_create_net("eps", 0444, net->sctp.proc_net_sctp,
+			&sctp_eps_ops, sizeof(struct seq_net_private)))
+		goto cleanup;
+	if (!proc_create_net("assocs", 0444, net->sctp.proc_net_sctp,
+			&sctp_assoc_ops, sizeof(struct sctp_ht_iter)))
+		goto cleanup;
+	if (!proc_create_net("remaddr", 0444, net->sctp.proc_net_sctp,
+			&sctp_remaddr_ops, sizeof(struct sctp_ht_iter)))
+		goto cleanup;
+	return 0;
+
+cleanup:
+	remove_proc_subtree("sctp", net->proc_net);
+	net->sctp.proc_net_sctp = NULL;
+	return -ENOMEM;
+}