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, 112 insertions, 0 deletions

diff --git a/drivers/video/fbdev/sm712.h b/drivers/video/fbdev/sm712.h
new file mode 100644
index 000000000..83fe25fc6
--- /dev/null
+++ b/drivers/video/fbdev/sm712.h
@@ -0,0 +1,112 @@
+/*
+ * Silicon Motion SM712 frame buffer device
+ *
+ * Copyright (C) 2006 Silicon Motion Technology Corp.
+ * Authors:	Ge Wang, gewang@siliconmotion.com
+ *		Boyod boyod.yang@siliconmotion.com.cn
+ *
+ * Copyright (C) 2009 Lemote, Inc.
+ * Author: Wu Zhangjin, wuzhangjin@gmail.com
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License. See the file COPYING in the main directory of this archive for
+ *  more details.
+ */
+
+#define FB_ACCEL_SMI_LYNX 88
+
+#define SCREEN_X_RES          1024
+#define SCREEN_Y_RES_PC       768
+#define SCREEN_Y_RES_NETBOOK  600
+#define SCREEN_BPP            16
+
+#define dac_reg	(0x3c8)
+#define dac_val	(0x3c9)
+
+extern void __iomem *smtc_regbaseaddress;
+#define smtc_mmiowb(dat, reg)	writeb(dat, smtc_regbaseaddress + reg)
+
+#define smtc_mmiorb(reg)	readb(smtc_regbaseaddress + reg)
+
+#define SIZE_SR00_SR04      (0x04 - 0x00 + 1)
+#define SIZE_SR10_SR24      (0x24 - 0x10 + 1)
+#define SIZE_SR30_SR75      (0x75 - 0x30 + 1)
+#define SIZE_SR80_SR93      (0x93 - 0x80 + 1)
+#define SIZE_SRA0_SRAF      (0xAF - 0xA0 + 1)
+#define SIZE_GR00_GR08      (0x08 - 0x00 + 1)
+#define SIZE_AR00_AR14      (0x14 - 0x00 + 1)
+#define SIZE_CR00_CR18      (0x18 - 0x00 + 1)
+#define SIZE_CR30_CR4D      (0x4D - 0x30 + 1)
+#define SIZE_CR90_CRA7      (0xA7 - 0x90 + 1)
+
+static inline void smtc_crtcw(int reg, int val)
+{
+	smtc_mmiowb(reg, 0x3d4);
+	smtc_mmiowb(val, 0x3d5);
+}
+
+static inline void smtc_grphw(int reg, int val)
+{
+	smtc_mmiowb(reg, 0x3ce);
+	smtc_mmiowb(val, 0x3cf);
+}
+
+static inline void smtc_attrw(int reg, int val)
+{
+	smtc_mmiorb(0x3da);
+	smtc_mmiowb(reg, 0x3c0);
+	smtc_mmiorb(0x3c1);
+	smtc_mmiowb(val, 0x3c0);
+}
+
+static inline void smtc_seqw(int reg, int val)
+{
+	smtc_mmiowb(reg, 0x3c4);
+	smtc_mmiowb(val, 0x3c5);
+}
+
+static inline unsigned int smtc_seqr(int reg)
+{
+	smtc_mmiowb(reg, 0x3c4);
+	return smtc_mmiorb(0x3c5);
+}
+
+/* The next structure holds all information relevant for a specific video mode.
+ */
+
+struct modeinit {
+	int mmsizex;
+	int mmsizey;
+	int bpp;
+	int hz;
+	unsigned char init_misc;
+	unsigned char init_sr00_sr04[SIZE_SR00_SR04];
+	unsigned char init_sr10_sr24[SIZE_SR10_SR24];
+	unsigned char init_sr30_sr75[SIZE_SR30_SR75];
+	unsigned char init_sr80_sr93[SIZE_SR80_SR93];
+	unsigned char init_sra0_sraf[SIZE_SRA0_SRAF];
+	unsigned char init_gr00_gr08[SIZE_GR00_GR08];
+	unsigned char init_ar00_ar14[SIZE_AR00_AR14];
+	unsigned char init_cr00_cr18[SIZE_CR00_CR18];
+	unsigned char init_cr30_cr4d[SIZE_CR30_CR4D];
+	unsigned char init_cr90_cra7[SIZE_CR90_CRA7];
+};
+
+#ifdef __BIG_ENDIAN
+#define pal_rgb(r, g, b, val)	(((r & 0xf800) >> 8) | \
+				((g & 0xe000) >> 13) | \
+				((g & 0x1c00) << 3) | \
+				((b & 0xf800) >> 3))
+#define big_addr		0x800000
+#define mmio_addr		0x00800000
+#define seqw17()		smtc_seqw(0x17, 0x30)
+#define big_pixel_depth(p, d)	{if (p == 24) {p = 32; d = 32; } }
+#define big_swap(p)		(((p & 0xff00ff00) >> 8) | ((p & 0x00ff00ff) << 8))
+#else
+#define pal_rgb(r, g, b, val)	val
+#define big_addr		0
+#define mmio_addr		0x00c00000
+#define seqw17()		do { } while (0)
+#define big_pixel_depth(p, d)	do { } while (0)
+#define big_swap(p)		p
+#endif