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, 230 insertions, 0 deletions

diff --git a/drivers/video/fbdev/g364fb.c b/drivers/video/fbdev/g364fb.c
new file mode 100644
index 000000000..ee6fe51e0
--- /dev/null
+++ b/drivers/video/fbdev/g364fb.c
@@ -0,0 +1,230 @@
+/* $Id: g364fb.c,v 1.3 1998/08/28 22:43:00 tsbogend Exp $
+ *
+ * linux/drivers/video/g364fb.c -- Mips Magnum frame buffer device
+ *
+ * (C) 1998 Thomas Bogendoerfer
+ *
+ *  This driver is based on tgafb.c
+ *
+ *	Copyright (C) 1997 Geert Uytterhoeven
+ *	Copyright (C) 1995  Jay Estabrook
+ *
+ *  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.
+ */
+
+#include <linux/module.h>
+#include <linux/console.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <asm/io.h>
+#include <asm/jazz.h>
+
+/*
+ * Various defines for the G364
+ */
+#define G364_MEM_BASE   0xe4400000
+#define G364_PORT_BASE  0xe4000000
+#define ID_REG 		0xe4000000	/* Read only */
+#define BOOT_REG 	0xe4080000
+#define TIMING_REG 	0xe4080108	/* to 0x080170 - DON'T TOUCH! */
+#define DISPLAY_REG 	0xe4080118
+#define VDISPLAY_REG 	0xe4080150
+#define MASK_REG 	0xe4080200
+#define CTLA_REG 	0xe4080300
+#define CURS_TOGGLE 	0x800000
+#define BIT_PER_PIX	0x700000	/* bits 22 to 20 of Control A */
+#define DELAY_SAMPLE    0x080000
+#define PORT_INTER	0x040000
+#define PIX_PIPE_DEL	0x030000	/* bits 17 and 16 of Control A */
+#define PIX_PIPE_DEL2	0x008000	/* same as above - don't ask me why */
+#define TR_CYCLE_TOG	0x004000
+#define VRAM_ADR_INC	0x003000	/* bits 13 and 12 of Control A */
+#define BLANK_OFF	0x000800
+#define FORCE_BLANK	0x000400
+#define BLK_FUN_SWTCH	0x000200
+#define BLANK_IO	0x000100
+#define BLANK_LEVEL	0x000080
+#define A_VID_FORM	0x000040
+#define D_SYNC_FORM	0x000020
+#define FRAME_FLY_PAT	0x000010
+#define OP_MODE		0x000008
+#define INTL_STAND	0x000004
+#define SCRN_FORM	0x000002
+#define ENABLE_VTG	0x000001
+#define TOP_REG 	0xe4080400
+#define CURS_PAL_REG 	0xe4080508	/* to 0x080518 */
+#define CHKSUM_REG 	0xe4080600	/* to 0x080610 - unused */
+#define CURS_POS_REG 	0xe4080638
+#define CLR_PAL_REG 	0xe4080800	/* to 0x080ff8 */
+#define CURS_PAT_REG 	0xe4081000	/* to 0x081ff8 */
+#define MON_ID_REG 	0xe4100000	/* unused */
+#define RESET_REG 	0xe4180000	/* Write only */
+
+static struct fb_info fb_info;
+
+static struct fb_fix_screeninfo fb_fix __initdata = {
+	.id 		= "G364 8plane",
+	.smem_start 	= 0x40000000,	/* physical address */
+	.type 		= FB_TYPE_PACKED_PIXELS,
+	.visual 	= FB_VISUAL_PSEUDOCOLOR,
+	.ypanstep 	= 1,
+	.accel 		= FB_ACCEL_NONE,
+};
+
+static struct fb_var_screeninfo fb_var __initdata = {
+	.bits_per_pixel = 8,
+	.red 		= { 0, 8, 0 },
+      	.green 		= { 0, 8, 0 },
+      	.blue		= { 0, 8, 0 },
+      	.activate	= FB_ACTIVATE_NOW,
+      	.height		= -1,
+      	.width		= -1,
+      	.pixclock	= 39722,
+      	.left_margin	= 40,
+      	.right_margin	= 24,
+      	.upper_margin	= 32,
+      	.lower_margin	= 11,
+      	.hsync_len 	= 96,
+      	.vsync_len 	= 2,
+      	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+/*
+ *  Interface used by the world
+ */
+int g364fb_init(void);
+
+static int g364fb_pan_display(struct fb_var_screeninfo *var,
+			      struct fb_info *info);
+static int g364fb_setcolreg(u_int regno, u_int red, u_int green,
+			    u_int blue, u_int transp,
+			    struct fb_info *info);
+static int g364fb_blank(int blank, struct fb_info *info);
+
+static const struct fb_ops g364fb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg	= g364fb_setcolreg,
+	.fb_pan_display	= g364fb_pan_display,
+	.fb_blank	= g364fb_blank,
+};
+
+/*
+ *  Pan or Wrap the Display
+ *
+ *  This call looks only at xoffset, yoffset and the FB_VMODE_YWRAP flag
+ */
+static int g364fb_pan_display(struct fb_var_screeninfo *var,
+			      struct fb_info *info)
+{
+	if (var->xoffset ||
+	    var->yoffset + info->var.yres > info->var.yres_virtual)
+		return -EINVAL;
+
+	*(unsigned int *) TOP_REG = var->yoffset * info->var.xres;
+	return 0;
+}
+
+/*
+ *  Blank the display.
+ */
+static int g364fb_blank(int blank, struct fb_info *info)
+{
+	if (blank)
+		*(unsigned int *) CTLA_REG |= FORCE_BLANK;
+	else
+		*(unsigned int *) CTLA_REG &= ~FORCE_BLANK;
+	return 0;
+}
+
+/*
+ *  Set a single color register. Return != 0 for invalid regno.
+ */
+static int g364fb_setcolreg(u_int regno, u_int red, u_int green,
+			    u_int blue, u_int transp, struct fb_info *info)
+{
+	volatile unsigned int *ptr = (volatile unsigned int *) CLR_PAL_REG;
+
+	if (regno > 255)
+		return 1;
+
+	red >>= 8;
+	green >>= 8;
+	blue >>= 8;
+
+	ptr[regno << 1] = (red << 16) | (green << 8) | blue;
+
+	return 0;
+}
+
+/*
+ *  Initialisation
+ */
+int __init g364fb_init(void)
+{
+	volatile unsigned int *curs_pal_ptr =
+	    (volatile unsigned int *) CURS_PAL_REG;
+	int mem, i;
+
+	if (fb_get_options("g364fb", NULL))
+		return -ENODEV;
+
+	/* TBD: G364 detection */
+
+	/* get the resolution set by ARC console */
+	*(volatile unsigned int *) CTLA_REG &= ~ENABLE_VTG;
+	fb_var.xres =
+	    (*((volatile unsigned int *) DISPLAY_REG) & 0x00ffffff) * 4;
+	fb_var.yres =
+	    (*((volatile unsigned int *) VDISPLAY_REG) & 0x00ffffff) / 2;
+	*(volatile unsigned int *) CTLA_REG |= ENABLE_VTG;
+
+	/* setup cursor */
+	curs_pal_ptr[0] |= 0x00ffffff;
+	curs_pal_ptr[2] |= 0x00ffffff;
+	curs_pal_ptr[4] |= 0x00ffffff;
+
+	/*
+	 * first set the whole cursor to transparent
+	 */
+	for (i = 0; i < 512; i++)
+		*(unsigned short *) (CURS_PAT_REG + i * 8) = 0;
+
+	/*
+	 * switch the last two lines to cursor palette 3
+	 * we assume here, that FONTSIZE_X is 8
+	 */
+	*(unsigned short *) (CURS_PAT_REG + 14 * 64) = 0xffff;
+	*(unsigned short *) (CURS_PAT_REG + 15 * 64) = 0xffff;
+	fb_var.xres_virtual = fb_var.xres;
+	fb_fix.line_length = fb_var.xres_virtual * fb_var.bits_per_pixel / 8;
+	fb_fix.smem_start = 0x40000000;	/* physical address */
+	/* get size of video memory; this is special for the JAZZ hardware */
+	mem = (r4030_read_reg32(JAZZ_R4030_CONFIG) >> 8) & 3;
+	fb_fix.smem_len = (1 << (mem * 2)) * 512 * 1024;
+	fb_var.yres_virtual = fb_fix.smem_len / fb_var.xres;
+
+	fb_info.fbops = &g364fb_ops;
+	fb_info.screen_base = (char *) G364_MEM_BASE;	/* virtual kernel address */
+	fb_info.var = fb_var;
+	fb_info.fix = fb_fix;
+	fb_info.flags = FBINFO_HWACCEL_YPAN;
+
+	fb_alloc_cmap(&fb_info.cmap, 255, 0);
+
+	if (register_framebuffer(&fb_info) < 0)
+		return -EINVAL;
+	return 0;
+}
+
+module_init(g364fb_init);
+MODULE_LICENSE("GPL");