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, 223 insertions, 0 deletions

diff --git a/net/6lowpan/ndisc.c b/net/6lowpan/ndisc.c
new file mode 100644
index 000000000..868d28583
--- /dev/null
+++ b/net/6lowpan/ndisc.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Authors:
+ * (C) 2016 Pengutronix, Alexander Aring <aar@pengutronix.de>
+ */
+
+#include <net/6lowpan.h>
+#include <net/addrconf.h>
+#include <net/ndisc.h>
+
+#include "6lowpan_i.h"
+
+#if IS_ENABLED(CONFIG_IEEE802154_6LOWPAN)
+#define NDISC_802154_SHORT_ADDR_LENGTH	1
+static int lowpan_ndisc_parse_802154_options(const struct net_device *dev,
+					     struct nd_opt_hdr *nd_opt,
+					     struct ndisc_options *ndopts)
+{
+	switch (nd_opt->nd_opt_len) {
+	case NDISC_802154_SHORT_ADDR_LENGTH:
+		if (ndopts->nd_802154_opt_array[nd_opt->nd_opt_type])
+			net_dbg_ratelimited("%s: duplicated short addr ND6 option found: type=%d\n",
+					    __func__, nd_opt->nd_opt_type);
+		else
+			ndopts->nd_802154_opt_array[nd_opt->nd_opt_type] = nd_opt;
+		return 1;
+	default:
+		/* all others will be handled by ndisc IPv6 option parsing */
+		return 0;
+	}
+}
+
+static int lowpan_ndisc_parse_options(const struct net_device *dev,
+				      struct nd_opt_hdr *nd_opt,
+				      struct ndisc_options *ndopts)
+{
+	if (!lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154))
+		return 0;
+
+	switch (nd_opt->nd_opt_type) {
+	case ND_OPT_SOURCE_LL_ADDR:
+	case ND_OPT_TARGET_LL_ADDR:
+		return lowpan_ndisc_parse_802154_options(dev, nd_opt, ndopts);
+	default:
+		return 0;
+	}
+}
+
+static void lowpan_ndisc_802154_update(struct neighbour *n, u32 flags,
+				       u8 icmp6_type,
+				       const struct ndisc_options *ndopts)
+{
+	struct lowpan_802154_neigh *neigh = lowpan_802154_neigh(neighbour_priv(n));
+	u8 *lladdr_short = NULL;
+
+	switch (icmp6_type) {
+	case NDISC_ROUTER_SOLICITATION:
+	case NDISC_ROUTER_ADVERTISEMENT:
+	case NDISC_NEIGHBOUR_SOLICITATION:
+		if (ndopts->nd_802154_opts_src_lladdr) {
+			lladdr_short = __ndisc_opt_addr_data(ndopts->nd_802154_opts_src_lladdr,
+							     IEEE802154_SHORT_ADDR_LEN, 0);
+			if (!lladdr_short) {
+				net_dbg_ratelimited("NA: invalid short link-layer address length\n");
+				return;
+			}
+		}
+		break;
+	case NDISC_REDIRECT:
+	case NDISC_NEIGHBOUR_ADVERTISEMENT:
+		if (ndopts->nd_802154_opts_tgt_lladdr) {
+			lladdr_short = __ndisc_opt_addr_data(ndopts->nd_802154_opts_tgt_lladdr,
+							     IEEE802154_SHORT_ADDR_LEN, 0);
+			if (!lladdr_short) {
+				net_dbg_ratelimited("NA: invalid short link-layer address length\n");
+				return;
+			}
+		}
+		break;
+	default:
+		break;
+	}
+
+	write_lock_bh(&n->lock);
+	if (lladdr_short) {
+		ieee802154_be16_to_le16(&neigh->short_addr, lladdr_short);
+		if (!lowpan_802154_is_valid_src_short_addr(neigh->short_addr))
+			neigh->short_addr = cpu_to_le16(IEEE802154_ADDR_SHORT_UNSPEC);
+	}
+	write_unlock_bh(&n->lock);
+}
+
+static void lowpan_ndisc_update(const struct net_device *dev,
+				struct neighbour *n, u32 flags, u8 icmp6_type,
+				const struct ndisc_options *ndopts)
+{
+	if (!lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154))
+		return;
+
+	/* react on overrides only. TODO check if this is really right. */
+	if (flags & NEIGH_UPDATE_F_OVERRIDE)
+		lowpan_ndisc_802154_update(n, flags, icmp6_type, ndopts);
+}
+
+static int lowpan_ndisc_opt_addr_space(const struct net_device *dev,
+				       u8 icmp6_type, struct neighbour *neigh,
+				       u8 *ha_buf, u8 **ha)
+{
+	struct lowpan_802154_neigh *n;
+	struct wpan_dev *wpan_dev;
+	int addr_space = 0;
+
+	if (!lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154))
+		return 0;
+
+	switch (icmp6_type) {
+	case NDISC_REDIRECT:
+		n = lowpan_802154_neigh(neighbour_priv(neigh));
+
+		read_lock_bh(&neigh->lock);
+		if (lowpan_802154_is_valid_src_short_addr(n->short_addr)) {
+			memcpy(ha_buf, &n->short_addr,
+			       IEEE802154_SHORT_ADDR_LEN);
+			read_unlock_bh(&neigh->lock);
+			addr_space += __ndisc_opt_addr_space(IEEE802154_SHORT_ADDR_LEN, 0);
+			*ha = ha_buf;
+		} else {
+			read_unlock_bh(&neigh->lock);
+		}
+		break;
+	case NDISC_NEIGHBOUR_ADVERTISEMENT:
+	case NDISC_NEIGHBOUR_SOLICITATION:
+	case NDISC_ROUTER_SOLICITATION:
+		wpan_dev = lowpan_802154_dev(dev)->wdev->ieee802154_ptr;
+
+		if (lowpan_802154_is_valid_src_short_addr(wpan_dev->short_addr))
+			addr_space = __ndisc_opt_addr_space(IEEE802154_SHORT_ADDR_LEN, 0);
+		break;
+	default:
+		break;
+	}
+
+	return addr_space;
+}
+
+static void lowpan_ndisc_fill_addr_option(const struct net_device *dev,
+					  struct sk_buff *skb, u8 icmp6_type,
+					  const u8 *ha)
+{
+	struct wpan_dev *wpan_dev;
+	__be16 short_addr;
+	u8 opt_type;
+
+	if (!lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154))
+		return;
+
+	switch (icmp6_type) {
+	case NDISC_REDIRECT:
+		if (ha) {
+			ieee802154_le16_to_be16(&short_addr, ha);
+			__ndisc_fill_addr_option(skb, ND_OPT_TARGET_LL_ADDR,
+						 &short_addr,
+						 IEEE802154_SHORT_ADDR_LEN, 0);
+		}
+		return;
+	case NDISC_NEIGHBOUR_ADVERTISEMENT:
+		opt_type = ND_OPT_TARGET_LL_ADDR;
+		break;
+	case NDISC_ROUTER_SOLICITATION:
+	case NDISC_NEIGHBOUR_SOLICITATION:
+		opt_type = ND_OPT_SOURCE_LL_ADDR;
+		break;
+	default:
+		return;
+	}
+
+	wpan_dev = lowpan_802154_dev(dev)->wdev->ieee802154_ptr;
+
+	if (lowpan_802154_is_valid_src_short_addr(wpan_dev->short_addr)) {
+		ieee802154_le16_to_be16(&short_addr,
+					&wpan_dev->short_addr);
+		__ndisc_fill_addr_option(skb, opt_type, &short_addr,
+					 IEEE802154_SHORT_ADDR_LEN, 0);
+	}
+}
+
+static void lowpan_ndisc_prefix_rcv_add_addr(struct net *net,
+					     struct net_device *dev,
+					     const struct prefix_info *pinfo,
+					     struct inet6_dev *in6_dev,
+					     struct in6_addr *addr,
+					     int addr_type, u32 addr_flags,
+					     bool sllao, bool tokenized,
+					     __u32 valid_lft,
+					     u32 prefered_lft,
+					     bool dev_addr_generated)
+{
+	int err;
+
+	/* generates short based address for RA PIO's */
+	if (lowpan_is_ll(dev, LOWPAN_LLTYPE_IEEE802154) && dev_addr_generated &&
+	    !addrconf_ifid_802154_6lowpan(addr->s6_addr + 8, dev)) {
+		err = addrconf_prefix_rcv_add_addr(net, dev, pinfo, in6_dev,
+						   addr, addr_type, addr_flags,
+						   sllao, tokenized, valid_lft,
+						   prefered_lft);
+		if (err)
+			net_dbg_ratelimited("RA: could not add a short address based address for prefix: %pI6c\n",
+					    &pinfo->prefix);
+	}
+}
+#endif
+
+const struct ndisc_ops lowpan_ndisc_ops = {
+#if IS_ENABLED(CONFIG_IEEE802154_6LOWPAN)
+	.parse_options		= lowpan_ndisc_parse_options,
+	.update			= lowpan_ndisc_update,
+	.opt_addr_space		= lowpan_ndisc_opt_addr_space,
+	.fill_addr_option	= lowpan_ndisc_fill_addr_option,
+	.prefix_rcv_add_addr	= lowpan_ndisc_prefix_rcv_add_addr,
+#endif
+};