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, 246 insertions, 0 deletions

diff --git a/net/mac80211/wme.c b/net/mac80211/wme.c
new file mode 100644
index 000000000..1601be576
--- /dev/null
+++ b/net/mac80211/wme.c
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2004, Instant802 Networks, Inc.
+ * Copyright 2013-2014  Intel Mobile Communications GmbH
+ * Copyright (C) 2022 Intel Corporation
+ */
+
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/module.h>
+#include <linux/if_arp.h>
+#include <linux/types.h>
+#include <net/ip.h>
+#include <net/pkt_sched.h>
+
+#include <net/mac80211.h>
+#include "ieee80211_i.h"
+#include "wme.h"
+
+/* Default mapping in classifier to work with default
+ * queue setup.
+ */
+const int ieee802_1d_to_ac[8] = {
+	IEEE80211_AC_BE,
+	IEEE80211_AC_BK,
+	IEEE80211_AC_BK,
+	IEEE80211_AC_BE,
+	IEEE80211_AC_VI,
+	IEEE80211_AC_VI,
+	IEEE80211_AC_VO,
+	IEEE80211_AC_VO
+};
+
+static int wme_downgrade_ac(struct sk_buff *skb)
+{
+	switch (skb->priority) {
+	case 6:
+	case 7:
+		skb->priority = 5; /* VO -> VI */
+		return 0;
+	case 4:
+	case 5:
+		skb->priority = 3; /* VI -> BE */
+		return 0;
+	case 0:
+	case 3:
+		skb->priority = 2; /* BE -> BK */
+		return 0;
+	default:
+		return -1;
+	}
+}
+
+/**
+ * ieee80211_fix_reserved_tid - return the TID to use if this one is reserved
+ * @tid: the assumed-reserved TID
+ *
+ * Returns: the alternative TID to use, or 0 on error
+ */
+static inline u8 ieee80211_fix_reserved_tid(u8 tid)
+{
+	switch (tid) {
+	case 0:
+		return 3;
+	case 1:
+		return 2;
+	case 2:
+		return 1;
+	case 3:
+		return 0;
+	case 4:
+		return 5;
+	case 5:
+		return 4;
+	case 6:
+		return 7;
+	case 7:
+		return 6;
+	}
+
+	return 0;
+}
+
+static u16 ieee80211_downgrade_queue(struct ieee80211_sub_if_data *sdata,
+				     struct sta_info *sta, struct sk_buff *skb)
+{
+	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
+
+	/* in case we are a client verify acm is not set for this ac */
+	while (sdata->wmm_acm & BIT(skb->priority)) {
+		int ac = ieee802_1d_to_ac[skb->priority];
+
+		if (ifmgd->tx_tspec[ac].admitted_time &&
+		    skb->priority == ifmgd->tx_tspec[ac].up)
+			return ac;
+
+		if (wme_downgrade_ac(skb)) {
+			/*
+			 * This should not really happen. The AP has marked all
+			 * lower ACs to require admission control which is not
+			 * a reasonable configuration. Allow the frame to be
+			 * transmitted using AC_BK as a workaround.
+			 */
+			break;
+		}
+	}
+
+	/* Check to see if this is a reserved TID */
+	if (sta && sta->reserved_tid == skb->priority)
+		skb->priority = ieee80211_fix_reserved_tid(skb->priority);
+
+	/* look up which queue to use for frames with this 1d tag */
+	return ieee802_1d_to_ac[skb->priority];
+}
+
+/* Indicate which queue to use for this fully formed 802.11 frame */
+u16 ieee80211_select_queue_80211(struct ieee80211_sub_if_data *sdata,
+				 struct sk_buff *skb,
+				 struct ieee80211_hdr *hdr)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	u8 *p;
+
+	/* Ensure hash is set prior to potential SW encryption */
+	skb_get_hash(skb);
+
+	if ((info->control.flags & IEEE80211_TX_CTRL_DONT_REORDER) ||
+	    local->hw.queues < IEEE80211_NUM_ACS)
+		return 0;
+
+	if (!ieee80211_is_data(hdr->frame_control)) {
+		skb->priority = 7;
+		return ieee802_1d_to_ac[skb->priority];
+	}
+	if (!ieee80211_is_data_qos(hdr->frame_control)) {
+		skb->priority = 0;
+		return ieee802_1d_to_ac[skb->priority];
+	}
+
+	p = ieee80211_get_qos_ctl(hdr);
+	skb->priority = *p & IEEE80211_QOS_CTL_TAG1D_MASK;
+
+	return ieee80211_downgrade_queue(sdata, NULL, skb);
+}
+
+u16 ieee80211_select_queue(struct ieee80211_sub_if_data *sdata,
+			   struct sta_info *sta, struct sk_buff *skb)
+{
+	const struct ethhdr *eth = (void *)skb->data;
+	struct mac80211_qos_map *qos_map;
+	bool qos;
+
+	/* Ensure hash is set prior to potential SW encryption */
+	skb_get_hash(skb);
+
+	/* all mesh/ocb stations are required to support WME */
+	if ((sdata->vif.type == NL80211_IFTYPE_MESH_POINT &&
+	    !is_multicast_ether_addr(eth->h_dest)) ||
+	    (sdata->vif.type == NL80211_IFTYPE_OCB && sta))
+		qos = true;
+	else if (sta)
+		qos = sta->sta.wme;
+	else
+		qos = false;
+
+	if (!qos) {
+		skb->priority = 0; /* required for correct WPA/11i MIC */
+		return IEEE80211_AC_BE;
+	}
+
+	if (skb->protocol == sdata->control_port_protocol) {
+		skb->priority = 7;
+		goto downgrade;
+	}
+
+	/* use the data classifier to determine what 802.1d tag the
+	 * data frame has */
+	qos_map = rcu_dereference(sdata->qos_map);
+	skb->priority = cfg80211_classify8021d(skb, qos_map ?
+					       &qos_map->qos_map : NULL);
+
+ downgrade:
+	return ieee80211_downgrade_queue(sdata, sta, skb);
+}
+
+/**
+ * ieee80211_set_qos_hdr - Fill in the QoS header if there is one.
+ *
+ * @sdata: local subif
+ * @skb: packet to be updated
+ */
+void ieee80211_set_qos_hdr(struct ieee80211_sub_if_data *sdata,
+			   struct sk_buff *skb)
+{
+	struct ieee80211_hdr *hdr = (void *)skb->data;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	u8 tid = skb->priority & IEEE80211_QOS_CTL_TAG1D_MASK;
+	u8 flags;
+	u8 *p;
+
+	if (!ieee80211_is_data_qos(hdr->frame_control))
+		return;
+
+	p = ieee80211_get_qos_ctl(hdr);
+
+	/* don't overwrite the QoS field of injected frames */
+	if (info->flags & IEEE80211_TX_CTL_INJECTED) {
+		/* do take into account Ack policy of injected frames */
+		if (*p & IEEE80211_QOS_CTL_ACK_POLICY_NOACK)
+			info->flags |= IEEE80211_TX_CTL_NO_ACK;
+		return;
+	}
+
+	/* set up the first byte */
+
+	/*
+	 * preserve everything but the TID and ACK policy
+	 * (which we both write here)
+	 */
+	flags = *p & ~(IEEE80211_QOS_CTL_TID_MASK |
+		       IEEE80211_QOS_CTL_ACK_POLICY_MASK);
+
+	if (is_multicast_ether_addr(hdr->addr1) ||
+	    sdata->noack_map & BIT(tid)) {
+		flags |= IEEE80211_QOS_CTL_ACK_POLICY_NOACK;
+		info->flags |= IEEE80211_TX_CTL_NO_ACK;
+	}
+
+	*p = flags | tid;
+
+	/* set up the second byte */
+	p++;
+
+	if (ieee80211_vif_is_mesh(&sdata->vif)) {
+		/* preserve RSPI and Mesh PS Level bit */
+		*p &= ((IEEE80211_QOS_CTL_RSPI |
+			IEEE80211_QOS_CTL_MESH_PS_LEVEL) >> 8);
+
+		/* Nulls don't have a mesh header (frame body) */
+		if (!ieee80211_is_qos_nullfunc(hdr->frame_control))
+			*p |= (IEEE80211_QOS_CTL_MESH_CONTROL_PRESENT >> 8);
+	} else {
+		*p = 0;
+	}
+}