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, 353 insertions, 0 deletions

diff --git a/arch/mips/math-emu/me-debugfs.c b/arch/mips/math-emu/me-debugfs.c
new file mode 100644
index 000000000..aeddf7aec
--- /dev/null
+++ b/arch/mips/math-emu/me-debugfs.c
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/cpumask.h>
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/percpu.h>
+#include <linux/types.h>
+#include <asm/debug.h>
+#include <asm/fpu_emulator.h>
+#include <asm/local.h>
+
+DEFINE_PER_CPU(struct mips_fpu_emulator_stats, fpuemustats);
+
+static int fpuemu_stat_get(void *data, u64 *val)
+{
+	int cpu;
+	unsigned long sum = 0;
+
+	for_each_online_cpu(cpu) {
+		struct mips_fpu_emulator_stats *ps;
+		local_t *pv;
+
+		ps = &per_cpu(fpuemustats, cpu);
+		pv = (void *)ps + (unsigned long)data;
+		sum += local_read(pv);
+	}
+	*val = sum;
+	return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(fops_fpuemu_stat, fpuemu_stat_get, NULL, "%llu\n");
+
+/*
+ * Used to obtain names for a debugfs instruction counter, given field name
+ * in fpuemustats structure. For example, for input "cmp_sueq_d", the output
+ * would be "cmp.sueq.d". This is needed since dots are not allowed to be
+ * used in structure field names, and are, on the other hand, desired to be
+ * used in debugfs item names to be clearly associated to corresponding
+ * MIPS FPU instructions.
+ */
+static void adjust_instruction_counter_name(char *out_name, char *in_name, size_t len)
+{
+	int i = 0;
+
+	strscpy(out_name, in_name, len);
+	while (in_name[i] != '\0') {
+		if (out_name[i] == '_')
+			out_name[i] = '.';
+		i++;
+	}
+}
+
+static int fpuemustats_clear_show(struct seq_file *s, void *unused)
+{
+	__this_cpu_write((fpuemustats).emulated, 0);
+	__this_cpu_write((fpuemustats).loads, 0);
+	__this_cpu_write((fpuemustats).stores, 0);
+	__this_cpu_write((fpuemustats).branches, 0);
+	__this_cpu_write((fpuemustats).cp1ops, 0);
+	__this_cpu_write((fpuemustats).cp1xops, 0);
+	__this_cpu_write((fpuemustats).errors, 0);
+	__this_cpu_write((fpuemustats).ieee754_inexact, 0);
+	__this_cpu_write((fpuemustats).ieee754_underflow, 0);
+	__this_cpu_write((fpuemustats).ieee754_overflow, 0);
+	__this_cpu_write((fpuemustats).ieee754_zerodiv, 0);
+	__this_cpu_write((fpuemustats).ieee754_invalidop, 0);
+	__this_cpu_write((fpuemustats).ds_emul, 0);
+
+	__this_cpu_write((fpuemustats).abs_s, 0);
+	__this_cpu_write((fpuemustats).abs_d, 0);
+	__this_cpu_write((fpuemustats).add_s, 0);
+	__this_cpu_write((fpuemustats).add_d, 0);
+	__this_cpu_write((fpuemustats).bc1eqz, 0);
+	__this_cpu_write((fpuemustats).bc1nez, 0);
+	__this_cpu_write((fpuemustats).ceil_w_s, 0);
+	__this_cpu_write((fpuemustats).ceil_w_d, 0);
+	__this_cpu_write((fpuemustats).ceil_l_s, 0);
+	__this_cpu_write((fpuemustats).ceil_l_d, 0);
+	__this_cpu_write((fpuemustats).class_s, 0);
+	__this_cpu_write((fpuemustats).class_d, 0);
+	__this_cpu_write((fpuemustats).cmp_af_s, 0);
+	__this_cpu_write((fpuemustats).cmp_af_d, 0);
+	__this_cpu_write((fpuemustats).cmp_eq_s, 0);
+	__this_cpu_write((fpuemustats).cmp_eq_d, 0);
+	__this_cpu_write((fpuemustats).cmp_le_s, 0);
+	__this_cpu_write((fpuemustats).cmp_le_d, 0);
+	__this_cpu_write((fpuemustats).cmp_lt_s, 0);
+	__this_cpu_write((fpuemustats).cmp_lt_d, 0);
+	__this_cpu_write((fpuemustats).cmp_ne_s, 0);
+	__this_cpu_write((fpuemustats).cmp_ne_d, 0);
+	__this_cpu_write((fpuemustats).cmp_or_s, 0);
+	__this_cpu_write((fpuemustats).cmp_or_d, 0);
+	__this_cpu_write((fpuemustats).cmp_ueq_s, 0);
+	__this_cpu_write((fpuemustats).cmp_ueq_d, 0);
+	__this_cpu_write((fpuemustats).cmp_ule_s, 0);
+	__this_cpu_write((fpuemustats).cmp_ule_d, 0);
+	__this_cpu_write((fpuemustats).cmp_ult_s, 0);
+	__this_cpu_write((fpuemustats).cmp_ult_d, 0);
+	__this_cpu_write((fpuemustats).cmp_un_s, 0);
+	__this_cpu_write((fpuemustats).cmp_un_d, 0);
+	__this_cpu_write((fpuemustats).cmp_une_s, 0);
+	__this_cpu_write((fpuemustats).cmp_une_d, 0);
+	__this_cpu_write((fpuemustats).cmp_saf_s, 0);
+	__this_cpu_write((fpuemustats).cmp_saf_d, 0);
+	__this_cpu_write((fpuemustats).cmp_seq_s, 0);
+	__this_cpu_write((fpuemustats).cmp_seq_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sle_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sle_d, 0);
+	__this_cpu_write((fpuemustats).cmp_slt_s, 0);
+	__this_cpu_write((fpuemustats).cmp_slt_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sne_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sne_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sor_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sor_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sueq_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sueq_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sule_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sule_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sult_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sult_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sun_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sun_d, 0);
+	__this_cpu_write((fpuemustats).cmp_sune_s, 0);
+	__this_cpu_write((fpuemustats).cmp_sune_d, 0);
+	__this_cpu_write((fpuemustats).cvt_d_l, 0);
+	__this_cpu_write((fpuemustats).cvt_d_s, 0);
+	__this_cpu_write((fpuemustats).cvt_d_w, 0);
+	__this_cpu_write((fpuemustats).cvt_l_s, 0);
+	__this_cpu_write((fpuemustats).cvt_l_d, 0);
+	__this_cpu_write((fpuemustats).cvt_s_d, 0);
+	__this_cpu_write((fpuemustats).cvt_s_l, 0);
+	__this_cpu_write((fpuemustats).cvt_s_w, 0);
+	__this_cpu_write((fpuemustats).cvt_w_s, 0);
+	__this_cpu_write((fpuemustats).cvt_w_d, 0);
+	__this_cpu_write((fpuemustats).div_s, 0);
+	__this_cpu_write((fpuemustats).div_d, 0);
+	__this_cpu_write((fpuemustats).floor_w_s, 0);
+	__this_cpu_write((fpuemustats).floor_w_d, 0);
+	__this_cpu_write((fpuemustats).floor_l_s, 0);
+	__this_cpu_write((fpuemustats).floor_l_d, 0);
+	__this_cpu_write((fpuemustats).maddf_s, 0);
+	__this_cpu_write((fpuemustats).maddf_d, 0);
+	__this_cpu_write((fpuemustats).max_s, 0);
+	__this_cpu_write((fpuemustats).max_d, 0);
+	__this_cpu_write((fpuemustats).maxa_s, 0);
+	__this_cpu_write((fpuemustats).maxa_d, 0);
+	__this_cpu_write((fpuemustats).min_s, 0);
+	__this_cpu_write((fpuemustats).min_d, 0);
+	__this_cpu_write((fpuemustats).mina_s, 0);
+	__this_cpu_write((fpuemustats).mina_d, 0);
+	__this_cpu_write((fpuemustats).mov_s, 0);
+	__this_cpu_write((fpuemustats).mov_d, 0);
+	__this_cpu_write((fpuemustats).msubf_s, 0);
+	__this_cpu_write((fpuemustats).msubf_d, 0);
+	__this_cpu_write((fpuemustats).mul_s, 0);
+	__this_cpu_write((fpuemustats).mul_d, 0);
+	__this_cpu_write((fpuemustats).neg_s, 0);
+	__this_cpu_write((fpuemustats).neg_d, 0);
+	__this_cpu_write((fpuemustats).recip_s, 0);
+	__this_cpu_write((fpuemustats).recip_d, 0);
+	__this_cpu_write((fpuemustats).rint_s, 0);
+	__this_cpu_write((fpuemustats).rint_d, 0);
+	__this_cpu_write((fpuemustats).round_w_s, 0);
+	__this_cpu_write((fpuemustats).round_w_d, 0);
+	__this_cpu_write((fpuemustats).round_l_s, 0);
+	__this_cpu_write((fpuemustats).round_l_d, 0);
+	__this_cpu_write((fpuemustats).rsqrt_s, 0);
+	__this_cpu_write((fpuemustats).rsqrt_d, 0);
+	__this_cpu_write((fpuemustats).sel_s, 0);
+	__this_cpu_write((fpuemustats).sel_d, 0);
+	__this_cpu_write((fpuemustats).seleqz_s, 0);
+	__this_cpu_write((fpuemustats).seleqz_d, 0);
+	__this_cpu_write((fpuemustats).selnez_s, 0);
+	__this_cpu_write((fpuemustats).selnez_d, 0);
+	__this_cpu_write((fpuemustats).sqrt_s, 0);
+	__this_cpu_write((fpuemustats).sqrt_d, 0);
+	__this_cpu_write((fpuemustats).sub_s, 0);
+	__this_cpu_write((fpuemustats).sub_d, 0);
+	__this_cpu_write((fpuemustats).trunc_w_s, 0);
+	__this_cpu_write((fpuemustats).trunc_w_d, 0);
+	__this_cpu_write((fpuemustats).trunc_l_s, 0);
+	__this_cpu_write((fpuemustats).trunc_l_d, 0);
+
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(fpuemustats_clear);
+
+static int __init debugfs_fpuemu(void)
+{
+	struct dentry *fpuemu_debugfs_base_dir;
+	struct dentry *fpuemu_debugfs_inst_dir;
+	char name[32];
+
+	fpuemu_debugfs_base_dir = debugfs_create_dir("fpuemustats",
+						     mips_debugfs_dir);
+
+	debugfs_create_file("fpuemustats_clear", 0444, mips_debugfs_dir, NULL,
+			    &fpuemustats_clear_fops);
+
+#define FPU_EMU_STAT_OFFSET(m)						\
+	offsetof(struct mips_fpu_emulator_stats, m)
+
+#define FPU_STAT_CREATE(m)						\
+do {									\
+	debugfs_create_file(#m, 0444, fpuemu_debugfs_base_dir,		\
+				(void *)FPU_EMU_STAT_OFFSET(m),		\
+				&fops_fpuemu_stat);			\
+} while (0)
+
+	FPU_STAT_CREATE(emulated);
+	FPU_STAT_CREATE(loads);
+	FPU_STAT_CREATE(stores);
+	FPU_STAT_CREATE(branches);
+	FPU_STAT_CREATE(cp1ops);
+	FPU_STAT_CREATE(cp1xops);
+	FPU_STAT_CREATE(errors);
+	FPU_STAT_CREATE(ieee754_inexact);
+	FPU_STAT_CREATE(ieee754_underflow);
+	FPU_STAT_CREATE(ieee754_overflow);
+	FPU_STAT_CREATE(ieee754_zerodiv);
+	FPU_STAT_CREATE(ieee754_invalidop);
+	FPU_STAT_CREATE(ds_emul);
+
+	fpuemu_debugfs_inst_dir = debugfs_create_dir("instructions",
+						     fpuemu_debugfs_base_dir);
+
+#define FPU_STAT_CREATE_EX(m)						\
+do {									\
+	adjust_instruction_counter_name(name, #m, sizeof(name));			\
+									\
+	debugfs_create_file(name, 0444, fpuemu_debugfs_inst_dir,	\
+				(void *)FPU_EMU_STAT_OFFSET(m),		\
+				&fops_fpuemu_stat);			\
+} while (0)
+
+	FPU_STAT_CREATE_EX(abs_s);
+	FPU_STAT_CREATE_EX(abs_d);
+	FPU_STAT_CREATE_EX(add_s);
+	FPU_STAT_CREATE_EX(add_d);
+	FPU_STAT_CREATE_EX(bc1eqz);
+	FPU_STAT_CREATE_EX(bc1nez);
+	FPU_STAT_CREATE_EX(ceil_w_s);
+	FPU_STAT_CREATE_EX(ceil_w_d);
+	FPU_STAT_CREATE_EX(ceil_l_s);
+	FPU_STAT_CREATE_EX(ceil_l_d);
+	FPU_STAT_CREATE_EX(class_s);
+	FPU_STAT_CREATE_EX(class_d);
+	FPU_STAT_CREATE_EX(cmp_af_s);
+	FPU_STAT_CREATE_EX(cmp_af_d);
+	FPU_STAT_CREATE_EX(cmp_eq_s);
+	FPU_STAT_CREATE_EX(cmp_eq_d);
+	FPU_STAT_CREATE_EX(cmp_le_s);
+	FPU_STAT_CREATE_EX(cmp_le_d);
+	FPU_STAT_CREATE_EX(cmp_lt_s);
+	FPU_STAT_CREATE_EX(cmp_lt_d);
+	FPU_STAT_CREATE_EX(cmp_ne_s);
+	FPU_STAT_CREATE_EX(cmp_ne_d);
+	FPU_STAT_CREATE_EX(cmp_or_s);
+	FPU_STAT_CREATE_EX(cmp_or_d);
+	FPU_STAT_CREATE_EX(cmp_ueq_s);
+	FPU_STAT_CREATE_EX(cmp_ueq_d);
+	FPU_STAT_CREATE_EX(cmp_ule_s);
+	FPU_STAT_CREATE_EX(cmp_ule_d);
+	FPU_STAT_CREATE_EX(cmp_ult_s);
+	FPU_STAT_CREATE_EX(cmp_ult_d);
+	FPU_STAT_CREATE_EX(cmp_un_s);
+	FPU_STAT_CREATE_EX(cmp_un_d);
+	FPU_STAT_CREATE_EX(cmp_une_s);
+	FPU_STAT_CREATE_EX(cmp_une_d);
+	FPU_STAT_CREATE_EX(cmp_saf_s);
+	FPU_STAT_CREATE_EX(cmp_saf_d);
+	FPU_STAT_CREATE_EX(cmp_seq_s);
+	FPU_STAT_CREATE_EX(cmp_seq_d);
+	FPU_STAT_CREATE_EX(cmp_sle_s);
+	FPU_STAT_CREATE_EX(cmp_sle_d);
+	FPU_STAT_CREATE_EX(cmp_slt_s);
+	FPU_STAT_CREATE_EX(cmp_slt_d);
+	FPU_STAT_CREATE_EX(cmp_sne_s);
+	FPU_STAT_CREATE_EX(cmp_sne_d);
+	FPU_STAT_CREATE_EX(cmp_sor_s);
+	FPU_STAT_CREATE_EX(cmp_sor_d);
+	FPU_STAT_CREATE_EX(cmp_sueq_s);
+	FPU_STAT_CREATE_EX(cmp_sueq_d);
+	FPU_STAT_CREATE_EX(cmp_sule_s);
+	FPU_STAT_CREATE_EX(cmp_sule_d);
+	FPU_STAT_CREATE_EX(cmp_sult_s);
+	FPU_STAT_CREATE_EX(cmp_sult_d);
+	FPU_STAT_CREATE_EX(cmp_sun_s);
+	FPU_STAT_CREATE_EX(cmp_sun_d);
+	FPU_STAT_CREATE_EX(cmp_sune_s);
+	FPU_STAT_CREATE_EX(cmp_sune_d);
+	FPU_STAT_CREATE_EX(cvt_d_l);
+	FPU_STAT_CREATE_EX(cvt_d_s);
+	FPU_STAT_CREATE_EX(cvt_d_w);
+	FPU_STAT_CREATE_EX(cvt_l_s);
+	FPU_STAT_CREATE_EX(cvt_l_d);
+	FPU_STAT_CREATE_EX(cvt_s_d);
+	FPU_STAT_CREATE_EX(cvt_s_l);
+	FPU_STAT_CREATE_EX(cvt_s_w);
+	FPU_STAT_CREATE_EX(cvt_w_s);
+	FPU_STAT_CREATE_EX(cvt_w_d);
+	FPU_STAT_CREATE_EX(div_s);
+	FPU_STAT_CREATE_EX(div_d);
+	FPU_STAT_CREATE_EX(floor_w_s);
+	FPU_STAT_CREATE_EX(floor_w_d);
+	FPU_STAT_CREATE_EX(floor_l_s);
+	FPU_STAT_CREATE_EX(floor_l_d);
+	FPU_STAT_CREATE_EX(maddf_s);
+	FPU_STAT_CREATE_EX(maddf_d);
+	FPU_STAT_CREATE_EX(max_s);
+	FPU_STAT_CREATE_EX(max_d);
+	FPU_STAT_CREATE_EX(maxa_s);
+	FPU_STAT_CREATE_EX(maxa_d);
+	FPU_STAT_CREATE_EX(min_s);
+	FPU_STAT_CREATE_EX(min_d);
+	FPU_STAT_CREATE_EX(mina_s);
+	FPU_STAT_CREATE_EX(mina_d);
+	FPU_STAT_CREATE_EX(mov_s);
+	FPU_STAT_CREATE_EX(mov_d);
+	FPU_STAT_CREATE_EX(msubf_s);
+	FPU_STAT_CREATE_EX(msubf_d);
+	FPU_STAT_CREATE_EX(mul_s);
+	FPU_STAT_CREATE_EX(mul_d);
+	FPU_STAT_CREATE_EX(neg_s);
+	FPU_STAT_CREATE_EX(neg_d);
+	FPU_STAT_CREATE_EX(recip_s);
+	FPU_STAT_CREATE_EX(recip_d);
+	FPU_STAT_CREATE_EX(rint_s);
+	FPU_STAT_CREATE_EX(rint_d);
+	FPU_STAT_CREATE_EX(round_w_s);
+	FPU_STAT_CREATE_EX(round_w_d);
+	FPU_STAT_CREATE_EX(round_l_s);
+	FPU_STAT_CREATE_EX(round_l_d);
+	FPU_STAT_CREATE_EX(rsqrt_s);
+	FPU_STAT_CREATE_EX(rsqrt_d);
+	FPU_STAT_CREATE_EX(sel_s);
+	FPU_STAT_CREATE_EX(sel_d);
+	FPU_STAT_CREATE_EX(seleqz_s);
+	FPU_STAT_CREATE_EX(seleqz_d);
+	FPU_STAT_CREATE_EX(selnez_s);
+	FPU_STAT_CREATE_EX(selnez_d);
+	FPU_STAT_CREATE_EX(sqrt_s);
+	FPU_STAT_CREATE_EX(sqrt_d);
+	FPU_STAT_CREATE_EX(sub_s);
+	FPU_STAT_CREATE_EX(sub_d);
+	FPU_STAT_CREATE_EX(trunc_w_s);
+	FPU_STAT_CREATE_EX(trunc_w_d);
+	FPU_STAT_CREATE_EX(trunc_l_s);
+	FPU_STAT_CREATE_EX(trunc_l_d);
+
+	return 0;
+}
+arch_initcall(debugfs_fpuemu);