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, 253 insertions, 0 deletions

diff --git a/net/bluetooth/hci_codec.c b/net/bluetooth/hci_codec.c
new file mode 100644
index 000000000..5bc5003c3
--- /dev/null
+++ b/net/bluetooth/hci_codec.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* Copyright (C) 2021 Intel Corporation */
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+#include "hci_codec.h"
+
+static int hci_codec_list_add(struct list_head *list,
+			      struct hci_op_read_local_codec_caps *sent,
+			      struct hci_rp_read_local_codec_caps *rp,
+			      void *caps,
+			      __u32 len)
+{
+	struct codec_list *entry;
+
+	entry = kzalloc(sizeof(*entry) + len, GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->id = sent->id;
+	if (sent->id == 0xFF) {
+		entry->cid = __le16_to_cpu(sent->cid);
+		entry->vid = __le16_to_cpu(sent->vid);
+	}
+	entry->transport = sent->transport;
+	entry->len = len;
+	entry->num_caps = 0;
+	if (rp) {
+		entry->num_caps = rp->num_caps;
+		memcpy(entry->caps, caps, len);
+	}
+	list_add(&entry->list, list);
+
+	return 0;
+}
+
+void hci_codec_list_clear(struct list_head *codec_list)
+{
+	struct codec_list *c, *n;
+
+	list_for_each_entry_safe(c, n, codec_list, list) {
+		list_del(&c->list);
+		kfree(c);
+	}
+}
+
+static void hci_read_codec_capabilities(struct hci_dev *hdev, __u8 transport,
+					struct hci_op_read_local_codec_caps
+					*cmd)
+{
+	__u8 i;
+
+	for (i = 0; i < TRANSPORT_TYPE_MAX; i++) {
+		if (transport & BIT(i)) {
+			struct hci_rp_read_local_codec_caps *rp;
+			struct hci_codec_caps *caps;
+			struct sk_buff *skb;
+			__u8 j;
+			__u32 len;
+
+			cmd->transport = i;
+
+			/* If Read_Codec_Capabilities command is not supported
+			 * then just add codec to the list without caps
+			 */
+			if (!(hdev->commands[45] & 0x08)) {
+				hci_dev_lock(hdev);
+				hci_codec_list_add(&hdev->local_codecs, cmd,
+						   NULL, NULL, 0);
+				hci_dev_unlock(hdev);
+				continue;
+			}
+
+			skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODEC_CAPS,
+						sizeof(*cmd), cmd, 0, HCI_CMD_TIMEOUT, NULL);
+			if (IS_ERR(skb)) {
+				bt_dev_err(hdev, "Failed to read codec capabilities (%ld)",
+					   PTR_ERR(skb));
+				continue;
+			}
+
+			if (skb->len < sizeof(*rp))
+				goto error;
+
+			rp = (void *)skb->data;
+
+			if (rp->status)
+				goto error;
+
+			if (!rp->num_caps) {
+				len = 0;
+				/* this codec doesn't have capabilities */
+				goto skip_caps_parse;
+			}
+
+			skb_pull(skb, sizeof(*rp));
+
+			for (j = 0, len = 0; j < rp->num_caps; j++) {
+				caps = (void *)skb->data;
+				if (skb->len < sizeof(*caps))
+					goto error;
+				if (skb->len < sizeof(caps->len) + caps->len)
+					goto error;
+				len += sizeof(caps->len) + caps->len;
+				skb_pull(skb,  sizeof(caps->len) + caps->len);
+			}
+
+skip_caps_parse:
+			hci_dev_lock(hdev);
+			hci_codec_list_add(&hdev->local_codecs, cmd, rp,
+					   (__u8 *)rp + sizeof(*rp), len);
+			hci_dev_unlock(hdev);
+error:
+			kfree_skb(skb);
+		}
+	}
+}
+
+void hci_read_supported_codecs(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct hci_rp_read_local_supported_codecs *rp;
+	struct hci_std_codecs *std_codecs;
+	struct hci_vnd_codecs *vnd_codecs;
+	struct hci_op_read_local_codec_caps caps;
+	__u8 i;
+
+	skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS, 0, NULL,
+				0, HCI_CMD_TIMEOUT, NULL);
+
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len < sizeof(*rp))
+		goto error;
+
+	rp = (void *)skb->data;
+
+	if (rp->status)
+		goto error;
+
+	skb_pull(skb, sizeof(rp->status));
+
+	std_codecs = (void *)skb->data;
+
+	/* validate codecs length before accessing */
+	if (skb->len < flex_array_size(std_codecs, codec, std_codecs->num)
+	    + sizeof(std_codecs->num))
+		goto error;
+
+	/* enumerate codec capabilities of standard codecs */
+	memset(&caps, 0, sizeof(caps));
+	for (i = 0; i < std_codecs->num; i++) {
+		caps.id = std_codecs->codec[i];
+		caps.direction = 0x00;
+		hci_read_codec_capabilities(hdev,
+					    LOCAL_CODEC_ACL_MASK | LOCAL_CODEC_SCO_MASK, &caps);
+	}
+
+	skb_pull(skb, flex_array_size(std_codecs, codec, std_codecs->num)
+		 + sizeof(std_codecs->num));
+
+	vnd_codecs = (void *)skb->data;
+
+	/* validate vendor codecs length before accessing */
+	if (skb->len <
+	    flex_array_size(vnd_codecs, codec, vnd_codecs->num)
+	    + sizeof(vnd_codecs->num))
+		goto error;
+
+	/* enumerate vendor codec capabilities */
+	for (i = 0; i < vnd_codecs->num; i++) {
+		caps.id = 0xFF;
+		caps.cid = vnd_codecs->codec[i].cid;
+		caps.vid = vnd_codecs->codec[i].vid;
+		caps.direction = 0x00;
+		hci_read_codec_capabilities(hdev,
+					    LOCAL_CODEC_ACL_MASK | LOCAL_CODEC_SCO_MASK, &caps);
+	}
+
+error:
+	kfree_skb(skb);
+}
+
+void hci_read_supported_codecs_v2(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+	struct hci_rp_read_local_supported_codecs_v2 *rp;
+	struct hci_std_codecs_v2 *std_codecs;
+	struct hci_vnd_codecs_v2 *vnd_codecs;
+	struct hci_op_read_local_codec_caps caps;
+	__u8 i;
+
+	skb = __hci_cmd_sync_sk(hdev, HCI_OP_READ_LOCAL_CODECS_V2, 0, NULL,
+				0, HCI_CMD_TIMEOUT, NULL);
+
+	if (IS_ERR(skb)) {
+		bt_dev_err(hdev, "Failed to read local supported codecs (%ld)",
+			   PTR_ERR(skb));
+		return;
+	}
+
+	if (skb->len < sizeof(*rp))
+		goto error;
+
+	rp = (void *)skb->data;
+
+	if (rp->status)
+		goto error;
+
+	skb_pull(skb, sizeof(rp->status));
+
+	std_codecs = (void *)skb->data;
+
+	/* check for payload data length before accessing */
+	if (skb->len < flex_array_size(std_codecs, codec, std_codecs->num)
+	    + sizeof(std_codecs->num))
+		goto error;
+
+	memset(&caps, 0, sizeof(caps));
+
+	for (i = 0; i < std_codecs->num; i++) {
+		caps.id = std_codecs->codec[i].id;
+		hci_read_codec_capabilities(hdev, std_codecs->codec[i].transport,
+					    &caps);
+	}
+
+	skb_pull(skb, flex_array_size(std_codecs, codec, std_codecs->num)
+		 + sizeof(std_codecs->num));
+
+	vnd_codecs = (void *)skb->data;
+
+	/* check for payload data length before accessing */
+	if (skb->len <
+	    flex_array_size(vnd_codecs, codec, vnd_codecs->num)
+	    + sizeof(vnd_codecs->num))
+		goto error;
+
+	for (i = 0; i < vnd_codecs->num; i++) {
+		caps.id = 0xFF;
+		caps.cid = vnd_codecs->codec[i].cid;
+		caps.vid = vnd_codecs->codec[i].vid;
+		hci_read_codec_capabilities(hdev, vnd_codecs->codec[i].transport,
+					    &caps);
+	}
+
+error:
+	kfree_skb(skb);
+}