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, 332 insertions, 0 deletions

diff --git a/drivers/nvme/target/debugfs.c b/drivers/nvme/target/debugfs.c
new file mode 100644
index 000000000..e85fe1d4c
--- /dev/null
+++ b/drivers/nvme/target/debugfs.c
@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DebugFS interface for the NVMe target.
+ * Copyright (c) 2022-2024 Shadow
+ * Copyright (c) 2024 SUSE LLC
+ */
+
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+
+#include "nvmet.h"
+#include "debugfs.h"
+
+static struct dentry *nvmet_debugfs;
+
+#define NVMET_DEBUGFS_ATTR(field) \
+	static int field##_open(struct inode *inode, struct file *file) \
+	{ return single_open(file, field##_show, inode->i_private); } \
+	\
+	static const struct file_operations field##_fops = { \
+		.open = field##_open, \
+		.read = seq_read, \
+		.release = single_release, \
+	}
+
+#define NVMET_DEBUGFS_RW_ATTR(field) \
+	static int field##_open(struct inode *inode, struct file *file) \
+	{ return single_open(file, field##_show, inode->i_private); } \
+	\
+	static const struct file_operations field##_fops = { \
+		.open = field##_open, \
+		.read = seq_read, \
+		.write = field##_write, \
+		.release = single_release, \
+	}
+
+static int nvmet_ctrl_hostnqn_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_puts(m, ctrl->hostnqn);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_hostnqn);
+
+static int nvmet_ctrl_kato_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_printf(m, "%d\n", ctrl->kato);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_kato);
+
+static int nvmet_ctrl_port_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_printf(m, "%d\n", le16_to_cpu(ctrl->port->disc_addr.portid));
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_port);
+
+static const char *const csts_state_names[] = {
+	[NVME_CSTS_RDY]		= "ready",
+	[NVME_CSTS_CFS]		= "fatal",
+	[NVME_CSTS_NSSRO]	= "reset",
+	[NVME_CSTS_SHST_OCCUR]	= "shutdown",
+	[NVME_CSTS_SHST_CMPLT]	= "completed",
+	[NVME_CSTS_PP]		= "paused",
+};
+
+static int nvmet_ctrl_state_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+	bool sep = false;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(csts_state_names); i++) {
+		int state = BIT(i);
+
+		if (!(ctrl->csts & state))
+			continue;
+		if (sep)
+			seq_puts(m, "|");
+		sep = true;
+		if (csts_state_names[state])
+			seq_puts(m, csts_state_names[state]);
+		else
+			seq_printf(m, "%d", state);
+	}
+	if (sep)
+		seq_printf(m, "\n");
+	return 0;
+}
+
+static ssize_t nvmet_ctrl_state_write(struct file *file, const char __user *buf,
+				      size_t count, loff_t *ppos)
+{
+	struct seq_file *m = file->private_data;
+	struct nvmet_ctrl *ctrl = m->private;
+	char reset[16];
+
+	if (count >= sizeof(reset))
+		return -EINVAL;
+	if (copy_from_user(reset, buf, count))
+		return -EFAULT;
+	if (!memcmp(reset, "fatal", 5))
+		nvmet_ctrl_fatal_error(ctrl);
+	else
+		return -EINVAL;
+	return count;
+}
+NVMET_DEBUGFS_RW_ATTR(nvmet_ctrl_state);
+
+static int nvmet_ctrl_host_traddr_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+	ssize_t size;
+	char buf[NVMF_TRADDR_SIZE + 1];
+
+	size = nvmet_ctrl_host_traddr(ctrl, buf, NVMF_TRADDR_SIZE);
+	if (size < 0) {
+		buf[0] = '\0';
+		size = 0;
+	}
+	buf[size] = '\0';
+	seq_printf(m, "%s\n", buf);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_host_traddr);
+
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+static int nvmet_ctrl_tls_key_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+	key_serial_t keyid = nvmet_queue_tls_keyid(ctrl->sqs[0]);
+
+	seq_printf(m, "%08x\n", keyid);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_tls_key);
+
+static int nvmet_ctrl_tls_concat_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ctrl *ctrl = m->private;
+
+	seq_printf(m, "%d\n", ctrl->concat);
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ctrl_tls_concat);
+#endif
+
+static const char *const nvmet_pr_type_names[] = {
+	[NVME_PR_WRITE_EXCLUSIVE]		= "write_exclusive",
+	[NVME_PR_EXCLUSIVE_ACCESS]		= "exclusive_access",
+	[NVME_PR_WRITE_EXCLUSIVE_REG_ONLY]	= "write_exclusive_reg_only",
+	[NVME_PR_EXCLUSIVE_ACCESS_REG_ONLY]	= "exclusive_access_reg_only",
+	[NVME_PR_WRITE_EXCLUSIVE_ALL_REGS]	= "write_exclusive_all_regs",
+	[NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS]	= "exclusive_access_all_regs",
+};
+
+static const char *nvmet_pr_type_to_str(enum nvme_pr_type type)
+{
+	if (type < ARRAY_SIZE(nvmet_pr_type_names) &&
+	    nvmet_pr_type_names[type])
+		return nvmet_pr_type_names[type];
+	return "unknown";
+}
+
+static const char *const nvmet_pr_notify_names[] = {
+	[NVME_PR_NOTIFY_BIT_REG_PREEMPTED]	= "reg_preempted",
+	[NVME_PR_NOTIFY_BIT_RESV_RELEASED]	= "resv_released",
+	[NVME_PR_NOTIFY_BIT_RESV_PREEMPTED]	= "resv_preempted",
+};
+
+static void nvmet_pr_notify_mask_to_str(struct seq_file *m, unsigned long mask)
+{
+	bool sep = false;
+	int i;
+
+	if (!mask) {
+		seq_puts(m, "none");
+		return;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(nvmet_pr_notify_names); i++) {
+		if (!test_bit(i, &mask) || !nvmet_pr_notify_names[i])
+			continue;
+		if (sep)
+			seq_putc(m, ',');
+		seq_puts(m, nvmet_pr_notify_names[i]);
+		sep = true;
+	}
+}
+
+static int nvmet_ns_pr_show(struct seq_file *m, void *p)
+{
+	struct nvmet_ns *ns = m->private;
+	struct nvmet_pr *pr = &ns->pr;
+	struct nvmet_pr_registrant *holder, *reg;
+
+	seq_printf(m, "enable=%d\n", pr->enable);
+	if (!pr->enable)
+		return 0;
+
+	seq_printf(m, "generation=%u\n", atomic_read(&pr->generation));
+	seq_puts(m, "notify_mask=");
+	nvmet_pr_notify_mask_to_str(m, pr->notify_mask);
+	seq_putc(m, '\n');
+
+	rcu_read_lock();
+	holder = rcu_dereference(pr->holder);
+	if (holder) {
+		seq_printf(m, "rtype=%s\n",
+			   nvmet_pr_type_to_str(holder->rtype));
+		seq_printf(m, "holder=%pUb,0x%llx\n",
+			   &holder->hostid, holder->rkey);
+	} else {
+		seq_puts(m, "rtype=none\n");
+		seq_puts(m, "holder=none\n");
+	}
+
+	list_for_each_entry_rcu(reg, &pr->registrant_list, entry) {
+		seq_printf(m, "reg=%pUb,0x%llx\n",
+			   &reg->hostid, reg->rkey);
+	}
+	rcu_read_unlock();
+
+	return 0;
+}
+NVMET_DEBUGFS_ATTR(nvmet_ns_pr);
+
+void nvmet_debugfs_ns_setup(struct nvmet_ns *ns)
+{
+	char name[16];
+	struct dentry *parent = ns->subsys->debugfs_dir;
+
+	if (!parent)
+		return;
+	snprintf(name, sizeof(name), "ns%u", ns->nsid);
+	ns->debugfs_dir = debugfs_create_dir(name, parent);
+	if (IS_ERR(ns->debugfs_dir)) {
+		ns->debugfs_dir = NULL;
+		return;
+	}
+	debugfs_create_file("reservation", 0400, ns->debugfs_dir, ns,
+			    &nvmet_ns_pr_fops);
+}
+
+void nvmet_debugfs_ns_free(struct nvmet_ns *ns)
+{
+	debugfs_remove_recursive(ns->debugfs_dir);
+	ns->debugfs_dir = NULL;
+}
+
+int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl)
+{
+	char name[32];
+	struct dentry *parent = ctrl->subsys->debugfs_dir;
+	int ret;
+
+	if (!parent)
+		return -ENODEV;
+	snprintf(name, sizeof(name), "ctrl%d", ctrl->cntlid);
+	ctrl->debugfs_dir = debugfs_create_dir(name, parent);
+	if (IS_ERR(ctrl->debugfs_dir)) {
+		ret = PTR_ERR(ctrl->debugfs_dir);
+		ctrl->debugfs_dir = NULL;
+		return ret;
+	}
+	debugfs_create_file("port", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_port_fops);
+	debugfs_create_file("hostnqn", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_hostnqn_fops);
+	debugfs_create_file("kato", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_kato_fops);
+	debugfs_create_file("state", S_IRUSR | S_IWUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_state_fops);
+	debugfs_create_file("host_traddr", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_host_traddr_fops);
+#ifdef CONFIG_NVME_TARGET_TCP_TLS
+	debugfs_create_file("tls_concat", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_tls_concat_fops);
+	debugfs_create_file("tls_key", S_IRUSR, ctrl->debugfs_dir, ctrl,
+			    &nvmet_ctrl_tls_key_fops);
+#endif
+	return 0;
+}
+
+void nvmet_debugfs_ctrl_free(struct nvmet_ctrl *ctrl)
+{
+	debugfs_remove_recursive(ctrl->debugfs_dir);
+}
+
+int nvmet_debugfs_subsys_setup(struct nvmet_subsys *subsys)
+{
+	int ret = 0;
+
+	subsys->debugfs_dir = debugfs_create_dir(subsys->subsysnqn,
+						 nvmet_debugfs);
+	if (IS_ERR(subsys->debugfs_dir)) {
+		ret = PTR_ERR(subsys->debugfs_dir);
+		subsys->debugfs_dir = NULL;
+	}
+	return ret;
+}
+
+void nvmet_debugfs_subsys_free(struct nvmet_subsys *subsys)
+{
+	debugfs_remove_recursive(subsys->debugfs_dir);
+}
+
+int __init nvmet_init_debugfs(void)
+{
+	struct dentry *parent;
+
+	parent = debugfs_create_dir("nvmet", NULL);
+	if (IS_ERR(parent)) {
+		pr_warn("%s: failed to create debugfs directory\n", "nvmet");
+		return PTR_ERR(parent);
+	}
+	nvmet_debugfs = parent;
+	return 0;
+}
+
+void nvmet_exit_debugfs(void)
+{
+	debugfs_remove_recursive(nvmet_debugfs);
+}