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, 236 insertions, 0 deletions

diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
new file mode 100644
index 000000000..2058fabff
--- /dev/null
+++ b/include/net/sctp/command.h
@@ -0,0 +1,236 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SCTP kernel Implementation
+ * (C) Copyright IBM Corp. 2001, 2004
+ * Copyright (C) 1999-2001 Cisco, Motorola
+ *
+ * This file is part of the SCTP kernel implementation
+ *
+ * These are the definitions needed for the command object.
+ *
+ * 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:
+ *   La Monte H.P. Yarroll <piggy@acm.org>
+ *   Karl Knutson <karl@athena.chicago.il.us>
+ *   Ardelle Fan <ardelle.fan@intel.com>
+ *   Sridhar Samudrala <sri@us.ibm.com>
+ */
+
+#ifndef __net_sctp_command_h__
+#define __net_sctp_command_h__
+
+#include <net/sctp/constants.h>
+#include <net/sctp/structs.h>
+
+
+enum sctp_verb {
+	SCTP_CMD_NOP = 0,	/* Do nothing. */
+	SCTP_CMD_NEW_ASOC,	/* Register a new association.  */
+	SCTP_CMD_DELETE_TCB,	/* Delete the current association. */
+	SCTP_CMD_NEW_STATE,	/* Enter a new state.  */
+	SCTP_CMD_REPORT_TSN,	/* Record the arrival of a TSN.  */
+	SCTP_CMD_GEN_SACK,	/* Send a Selective ACK (maybe).  */
+	SCTP_CMD_PROCESS_SACK,	/* Process an inbound SACK.  */
+	SCTP_CMD_GEN_INIT_ACK,	/* Generate an INIT ACK chunk.  */
+	SCTP_CMD_PEER_INIT,	/* Process a INIT from the peer.  */
+	SCTP_CMD_GEN_COOKIE_ECHO, /* Generate a COOKIE ECHO chunk. */
+	SCTP_CMD_CHUNK_ULP,	/* Send a chunk to the sockets layer.  */
+	SCTP_CMD_EVENT_ULP,	/* Send a notification to the sockets layer. */
+	SCTP_CMD_REPLY,		/* Send a chunk to our peer.  */
+	SCTP_CMD_SEND_PKT,	/* Send a full packet to our peer.  */
+	SCTP_CMD_RETRAN,	/* Mark a transport for retransmission.  */
+	SCTP_CMD_ECN_CE,        /* Do delayed CE processing.   */
+	SCTP_CMD_ECN_ECNE,	/* Do delayed ECNE processing. */
+	SCTP_CMD_ECN_CWR,	/* Do delayed CWR processing.  */
+	SCTP_CMD_TIMER_START,	/* Start a timer.  */
+	SCTP_CMD_TIMER_START_ONCE, /* Start a timer once */
+	SCTP_CMD_TIMER_RESTART,	/* Restart a timer. */
+	SCTP_CMD_TIMER_STOP,	/* Stop a timer. */
+	SCTP_CMD_INIT_CHOOSE_TRANSPORT, /* Choose transport for an INIT. */
+	SCTP_CMD_INIT_COUNTER_RESET, /* Reset init counter. */
+	SCTP_CMD_INIT_COUNTER_INC,   /* Increment init counter. */
+	SCTP_CMD_INIT_RESTART,  /* High level, do init timer work. */
+	SCTP_CMD_COOKIEECHO_RESTART,  /* High level, do cookie-echo timer work. */
+	SCTP_CMD_INIT_FAILED,   /* High level, do init failure work. */
+	SCTP_CMD_REPORT_DUP,	/* Report a duplicate TSN.  */
+	SCTP_CMD_STRIKE,	/* Mark a strike against a transport.  */
+	SCTP_CMD_HB_TIMERS_START,    /* Start the heartbeat timers. */
+	SCTP_CMD_HB_TIMER_UPDATE,    /* Update a heartbeat timers.  */
+	SCTP_CMD_HB_TIMERS_STOP,     /* Stop the heartbeat timers.  */
+	SCTP_CMD_PROBE_TIMER_UPDATE, /* Update a probe timer.  */
+	SCTP_CMD_TRANSPORT_HB_SENT,  /* Reset the status of a transport. */
+	SCTP_CMD_TRANSPORT_IDLE,     /* Do manipulations on idle transport */
+	SCTP_CMD_TRANSPORT_ON,       /* Mark the transport as active. */
+	SCTP_CMD_REPORT_ERROR,   /* Pass this error back out of the sm. */
+	SCTP_CMD_REPORT_BAD_TAG, /* Verification tags didn't match. */
+	SCTP_CMD_PROCESS_CTSN,   /* Sideeffect from shutdown. */
+	SCTP_CMD_ASSOC_FAILED,	 /* Handle association failure. */
+	SCTP_CMD_DISCARD_PACKET, /* Discard the whole packet. */
+	SCTP_CMD_GEN_SHUTDOWN,   /* Generate a SHUTDOWN chunk. */
+	SCTP_CMD_PURGE_OUTQUEUE, /* Purge all data waiting to be sent. */
+	SCTP_CMD_SETUP_T2,       /* Hi-level, setup T2-shutdown parms.  */
+	SCTP_CMD_RTO_PENDING,	 /* Set transport's rto_pending. */
+	SCTP_CMD_PART_DELIVER,	 /* Partial data delivery considerations. */
+	SCTP_CMD_RENEGE,         /* Renege data on an association. */
+	SCTP_CMD_SETUP_T4,	 /* ADDIP, setup T4 RTO timer parms. */
+	SCTP_CMD_PROCESS_OPERR,  /* Process an ERROR chunk. */
+	SCTP_CMD_REPORT_FWDTSN,	 /* Report new cumulative TSN Ack. */
+	SCTP_CMD_PROCESS_FWDTSN, /* Skips were reported, so process further. */
+	SCTP_CMD_CLEAR_INIT_TAG, /* Clears association peer's inittag. */
+	SCTP_CMD_DEL_NON_PRIMARY, /* Removes non-primary peer transports. */
+	SCTP_CMD_T3_RTX_TIMERS_STOP, /* Stops T3-rtx pending timers */
+	SCTP_CMD_FORCE_PRIM_RETRAN,  /* Forces retrans. over primary path. */
+	SCTP_CMD_SET_SK_ERR,	 /* Set sk_err */
+	SCTP_CMD_ASSOC_CHANGE,	 /* generate and send assoc_change event */
+	SCTP_CMD_ADAPTATION_IND, /* generate and send adaptation event */
+	SCTP_CMD_PEER_NO_AUTH,   /* generate and send authentication event */
+	SCTP_CMD_ASSOC_SHKEY,    /* generate the association shared keys */
+	SCTP_CMD_T1_RETRAN,	 /* Mark for retransmission after T1 timeout  */
+	SCTP_CMD_UPDATE_INITTAG, /* Update peer inittag */
+	SCTP_CMD_SEND_MSG,	 /* Send the whole use message */
+	SCTP_CMD_PURGE_ASCONF_QUEUE, /* Purge all asconf queues.*/
+	SCTP_CMD_SET_ASOC,	 /* Restore association context */
+	SCTP_CMD_LAST
+};
+
+/* How many commands can you put in an struct sctp_cmd_seq?
+ * This is a rather arbitrary number, ideally derived from a careful
+ * analysis of the state functions, but in reality just taken from
+ * thin air in the hopes othat we don't trigger a kernel panic.
+ */
+#define SCTP_MAX_NUM_COMMANDS 20
+
+union sctp_arg {
+	void *zero_all;	/* Set to NULL to clear the entire union */
+	__s32 i32;
+	__u32 u32;
+	__be32 be32;
+	__u16 u16;
+	__u8 u8;
+	int error;
+	__be16 err;
+	enum sctp_state state;
+	enum sctp_event_timeout to;
+	struct sctp_chunk *chunk;
+	struct sctp_association *asoc;
+	struct sctp_transport *transport;
+	struct sctp_bind_addr *bp;
+	struct sctp_init_chunk *init;
+	struct sctp_ulpevent *ulpevent;
+	struct sctp_packet *packet;
+	struct sctp_sackhdr *sackh;
+	struct sctp_datamsg *msg;
+};
+
+/* We are simulating ML type constructors here.
+ *
+ * SCTP_ARG_CONSTRUCTOR(NAME, TYPE, ELT) builds a function called
+ * SCTP_NAME() which takes an argument of type TYPE and returns an
+ * union sctp_arg.  It does this by inserting the sole argument into
+ * the ELT union element of a local union sctp_arg.
+ *
+ * E.g., SCTP_ARG_CONSTRUCTOR(I32, __s32, i32) builds SCTP_I32(arg),
+ * which takes an __s32 and returns a union sctp_arg containing the
+ * __s32.  So, after foo = SCTP_I32(arg), foo.i32 == arg.
+ */
+
+#define SCTP_ARG_CONSTRUCTOR(name, type, elt) \
+static inline union sctp_arg	\
+SCTP_## name (type arg)		\
+{ union sctp_arg retval;\
+  retval.zero_all = NULL;\
+  retval.elt = arg;\
+  return retval;\
+}
+
+SCTP_ARG_CONSTRUCTOR(I32,	__s32, i32)
+SCTP_ARG_CONSTRUCTOR(U32,	__u32, u32)
+SCTP_ARG_CONSTRUCTOR(BE32,	__be32, be32)
+SCTP_ARG_CONSTRUCTOR(U16,	__u16, u16)
+SCTP_ARG_CONSTRUCTOR(U8,	__u8, u8)
+SCTP_ARG_CONSTRUCTOR(ERROR,     int, error)
+SCTP_ARG_CONSTRUCTOR(PERR,      __be16, err)	/* protocol error */
+SCTP_ARG_CONSTRUCTOR(STATE,	enum sctp_state, state)
+SCTP_ARG_CONSTRUCTOR(TO,	enum sctp_event_timeout, to)
+SCTP_ARG_CONSTRUCTOR(CHUNK,	struct sctp_chunk *, chunk)
+SCTP_ARG_CONSTRUCTOR(ASOC,	struct sctp_association *, asoc)
+SCTP_ARG_CONSTRUCTOR(TRANSPORT,	struct sctp_transport *, transport)
+SCTP_ARG_CONSTRUCTOR(BA,	struct sctp_bind_addr *, bp)
+SCTP_ARG_CONSTRUCTOR(PEER_INIT,	struct sctp_init_chunk *, init)
+SCTP_ARG_CONSTRUCTOR(ULPEVENT,  struct sctp_ulpevent *, ulpevent)
+SCTP_ARG_CONSTRUCTOR(PACKET,	struct sctp_packet *, packet)
+SCTP_ARG_CONSTRUCTOR(SACKH,	struct sctp_sackhdr *, sackh)
+SCTP_ARG_CONSTRUCTOR(DATAMSG,	struct sctp_datamsg *, msg)
+
+static inline union sctp_arg SCTP_FORCE(void)
+{
+	return SCTP_I32(1);
+}
+
+static inline union sctp_arg SCTP_NOFORCE(void)
+{
+	return SCTP_I32(0);
+}
+
+static inline union sctp_arg SCTP_NULL(void)
+{
+	union sctp_arg retval;
+	retval.zero_all = NULL;
+	return retval;
+}
+
+struct sctp_cmd {
+	union sctp_arg obj;
+	enum sctp_verb verb;
+};
+
+struct sctp_cmd_seq {
+	struct sctp_cmd cmds[SCTP_MAX_NUM_COMMANDS];
+	struct sctp_cmd *last_used_slot;
+	struct sctp_cmd *next_cmd;
+};
+
+
+/* Initialize a block of memory as a command sequence.
+ * Return 0 if the initialization fails.
+ */
+static inline int sctp_init_cmd_seq(struct sctp_cmd_seq *seq)
+{
+	/* cmds[] is filled backwards to simplify the overflow BUG() check */
+	seq->last_used_slot = seq->cmds + SCTP_MAX_NUM_COMMANDS;
+	seq->next_cmd = seq->last_used_slot;
+	return 1;		/* We always succeed.  */
+}
+
+
+/* Add a command to an struct sctp_cmd_seq.
+ *
+ * Use the SCTP_* constructors defined by SCTP_ARG_CONSTRUCTOR() above
+ * to wrap data which goes in the obj argument.
+ */
+static inline void sctp_add_cmd_sf(struct sctp_cmd_seq *seq,
+				   enum sctp_verb verb, union sctp_arg obj)
+{
+	struct sctp_cmd *cmd = seq->last_used_slot - 1;
+
+	BUG_ON(cmd < seq->cmds);
+
+	cmd->verb = verb;
+	cmd->obj = obj;
+	seq->last_used_slot = cmd;
+}
+
+/* Return the next command structure in an sctp_cmd_seq.
+ * Return NULL at the end of the sequence.
+ */
+static inline struct sctp_cmd *sctp_next_cmd(struct sctp_cmd_seq *seq)
+{
+	if (seq->next_cmd <= seq->last_used_slot)
+		return NULL;
+
+	return --seq->next_cmd;
+}
+
+#endif /* __net_sctp_command_h__ */