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, 514 insertions, 0 deletions

diff --git a/drivers/video/fbdev/hitfb.c b/drivers/video/fbdev/hitfb.c
new file mode 100644
index 000000000..97db325df
--- /dev/null
+++ b/drivers/video/fbdev/hitfb.c
@@ -0,0 +1,514 @@
+/*
+ * linux/drivers/video/hitfb.c -- Hitachi LCD frame buffer device
+ *
+ * (C) 1999 Mihai Spatar
+ * (C) 2000 YAEGASHI Takeshi
+ * (C) 2003, 2004 Paul Mundt
+ * (C) 2003, 2004, 2006 Andriy Skulysh
+ *
+ *  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/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/fb.h>
+
+#include <asm/machvec.h>
+#include <linux/uaccess.h>
+#include <asm/io.h>
+#include <asm/hd64461.h>
+#include <cpu/dac.h>
+
+#define	WIDTH 640
+
+static struct fb_var_screeninfo hitfb_var = {
+	.activate	= FB_ACTIVATE_NOW,
+	.height		= -1,
+	.width		= -1,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+static struct fb_fix_screeninfo hitfb_fix = {
+	.id		= "Hitachi HD64461",
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.accel		= FB_ACCEL_NONE,
+};
+
+static volatile void __iomem *hitfb_offset_to_addr(unsigned int offset)
+{
+	return (__force volatile void __iomem *)(uintptr_t)offset;
+}
+
+static u16 hitfb_readw(unsigned int offset)
+{
+	return fb_readw(hitfb_offset_to_addr(offset));
+}
+
+static void hitfb_writew(u16 value, unsigned int offset)
+{
+	fb_writew(value, hitfb_offset_to_addr(offset));
+}
+
+static inline void hitfb_accel_wait(void)
+{
+	while (hitfb_readw(HD64461_GRCFGR) & HD64461_GRCFGR_ACCSTATUS)
+		;
+}
+
+static inline void hitfb_accel_start(int truecolor)
+{
+	if (truecolor) {
+		hitfb_writew(6, HD64461_GRCFGR);
+	} else {
+		hitfb_writew(7, HD64461_GRCFGR);
+	}
+}
+
+static inline void hitfb_accel_set_dest(int truecolor, u16 dx, u16 dy,
+					u16 width, u16 height)
+{
+	u32 saddr = WIDTH * dy + dx;
+	if (truecolor)
+		saddr <<= 1;
+
+	hitfb_writew(width-1, HD64461_BBTDWR);
+	hitfb_writew(height-1, HD64461_BBTDHR);
+
+	hitfb_writew(saddr & 0xffff, HD64461_BBTDSARL);
+	hitfb_writew(saddr >> 16, HD64461_BBTDSARH);
+
+}
+
+static inline void hitfb_accel_bitblt(int truecolor, u16 sx, u16 sy, u16 dx,
+				      u16 dy, u16 width, u16 height, u16 rop,
+				      u32 mask_addr)
+{
+	u32 saddr, daddr;
+	u32 maddr = 0;
+
+	height--;
+	width--;
+	hitfb_writew(rop, HD64461_BBTROPR);
+	if ((sy < dy) || ((sy == dy) && (sx <= dx))) {
+		saddr = WIDTH * (sy + height) + sx + width;
+		daddr = WIDTH * (dy + height) + dx + width;
+		if (mask_addr) {
+			if (truecolor)
+				maddr = ((width >> 3) + 1) * (height + 1) - 1;
+			else
+				maddr =
+				    (((width >> 4) + 1) * (height + 1) - 1) * 2;
+
+			hitfb_writew((1 << 5) | 1, HD64461_BBTMDR);
+		} else
+			hitfb_writew(1, HD64461_BBTMDR);
+	} else {
+		saddr = WIDTH * sy + sx;
+		daddr = WIDTH * dy + dx;
+		if (mask_addr) {
+			hitfb_writew((1 << 5), HD64461_BBTMDR);
+		} else {
+			hitfb_writew(0, HD64461_BBTMDR);
+		}
+	}
+	if (truecolor) {
+		saddr <<= 1;
+		daddr <<= 1;
+	}
+	hitfb_writew(width, HD64461_BBTDWR);
+	hitfb_writew(height, HD64461_BBTDHR);
+	hitfb_writew(saddr & 0xffff, HD64461_BBTSSARL);
+	hitfb_writew(saddr >> 16, HD64461_BBTSSARH);
+	hitfb_writew(daddr & 0xffff, HD64461_BBTDSARL);
+	hitfb_writew(daddr >> 16, HD64461_BBTDSARH);
+	if (mask_addr) {
+		maddr += mask_addr;
+		hitfb_writew(maddr & 0xffff, HD64461_BBTMARL);
+		hitfb_writew(maddr >> 16, HD64461_BBTMARH);
+	}
+	hitfb_accel_start(truecolor);
+}
+
+static void hitfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
+{
+	if (rect->rop != ROP_COPY)
+		cfb_fillrect(p, rect);
+	else {
+		hitfb_accel_wait();
+		hitfb_writew(0x00f0, HD64461_BBTROPR);
+		hitfb_writew(16, HD64461_BBTMDR);
+
+		if (p->var.bits_per_pixel == 16) {
+			hitfb_writew(((u32 *) (p->pseudo_palette))[rect->color],
+				  HD64461_GRSCR);
+			hitfb_accel_set_dest(1, rect->dx, rect->dy, rect->width,
+					     rect->height);
+			hitfb_accel_start(1);
+		} else {
+			hitfb_writew(rect->color, HD64461_GRSCR);
+			hitfb_accel_set_dest(0, rect->dx, rect->dy, rect->width,
+					     rect->height);
+			hitfb_accel_start(0);
+		}
+	}
+}
+
+static void hitfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
+{
+	hitfb_accel_wait();
+	hitfb_accel_bitblt(p->var.bits_per_pixel == 16, area->sx, area->sy,
+			   area->dx, area->dy, area->width, area->height,
+			   0x00cc, 0);
+}
+
+static int hitfb_pan_display(struct fb_var_screeninfo *var,
+			     struct fb_info *info)
+{
+	int xoffset = var->xoffset;
+	int yoffset = var->yoffset;
+
+	if (xoffset != 0)
+		return -EINVAL;
+
+	hitfb_writew((yoffset*info->fix.line_length)>>10, HD64461_LCDCBAR);
+
+	return 0;
+}
+
+static int hitfb_blank(int blank_mode, struct fb_info *info)
+{
+	unsigned short v;
+
+	if (blank_mode) {
+		v = hitfb_readw(HD64461_LDR1);
+		v &= ~HD64461_LDR1_DON;
+		hitfb_writew(v, HD64461_LDR1);
+
+		v = hitfb_readw(HD64461_LCDCCR);
+		v |= HD64461_LCDCCR_MOFF;
+		hitfb_writew(v, HD64461_LCDCCR);
+
+		v = hitfb_readw(HD64461_STBCR);
+		v |= HD64461_STBCR_SLCDST;
+		hitfb_writew(v, HD64461_STBCR);
+	} else {
+		v = hitfb_readw(HD64461_STBCR);
+		v &= ~HD64461_STBCR_SLCDST;
+		hitfb_writew(v, HD64461_STBCR);
+
+		v = hitfb_readw(HD64461_LCDCCR);
+		v &= ~(HD64461_LCDCCR_MOFF | HD64461_LCDCCR_STREQ);
+		hitfb_writew(v, HD64461_LCDCCR);
+
+		do {
+		    v = hitfb_readw(HD64461_LCDCCR);
+		} while(v&HD64461_LCDCCR_STBACK);
+
+		v = hitfb_readw(HD64461_LDR1);
+		v |= HD64461_LDR1_DON;
+		hitfb_writew(v, HD64461_LDR1);
+	}
+	return 0;
+}
+
+static int hitfb_setcolreg(unsigned regno, unsigned red, unsigned green,
+			   unsigned blue, unsigned transp, struct fb_info *info)
+{
+	if (regno >= 256)
+		return 1;
+
+	switch (info->var.bits_per_pixel) {
+	case 8:
+		hitfb_writew(regno << 8, HD64461_CPTWAR);
+		hitfb_writew(red >> 10, HD64461_CPTWDR);
+		hitfb_writew(green >> 10, HD64461_CPTWDR);
+		hitfb_writew(blue >> 10, HD64461_CPTWDR);
+		break;
+	case 16:
+		if (regno >= 16)
+			return 1;
+		((u32 *) (info->pseudo_palette))[regno] =
+		    ((red & 0xf800)) |
+		    ((green & 0xfc00) >> 5) | ((blue & 0xf800) >> 11);
+		break;
+	}
+	return 0;
+}
+
+static int hitfb_sync(struct fb_info *info)
+{
+	hitfb_accel_wait();
+
+	return 0;
+}
+
+static int hitfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	int maxy;
+
+	var->xres = info->var.xres;
+	var->xres_virtual = info->var.xres;
+	var->yres = info->var.yres;
+
+	if ((var->bits_per_pixel != 8) && (var->bits_per_pixel != 16))
+		var->bits_per_pixel = info->var.bits_per_pixel;
+
+	if (var->yres_virtual < var->yres)
+		var->yres_virtual = var->yres;
+
+	maxy = info->fix.smem_len / var->xres;
+
+	if (var->bits_per_pixel == 16)
+		maxy /= 2;
+
+	if (var->yres_virtual > maxy)
+		var->yres_virtual = maxy;
+
+	var->xoffset = 0;
+	var->yoffset = 0;
+
+	switch (var->bits_per_pixel) {
+	case 8:
+		var->red.offset = 0;
+		var->red.length = 8;
+		var->green.offset = 0;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	case 16:		/* RGB 565 */
+		var->red.offset = 11;
+		var->red.length = 5;
+		var->green.offset = 5;
+		var->green.length = 6;
+		var->blue.offset = 0;
+		var->blue.length = 5;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	}
+
+	return 0;
+}
+
+static int hitfb_set_par(struct fb_info *info)
+{
+	unsigned short ldr3;
+
+	switch (info->var.bits_per_pixel) {
+	case 8:
+		info->fix.line_length = info->var.xres;
+		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
+		info->fix.ypanstep = 16;
+		break;
+	case 16:
+		info->fix.line_length = info->var.xres*2;
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+		info->fix.ypanstep = 8;
+		break;
+	}
+
+	hitfb_writew(info->fix.line_length, HD64461_LCDCLOR);
+	ldr3 = hitfb_readw(HD64461_LDR3);
+	ldr3 &= ~15;
+	ldr3 |= (info->var.bits_per_pixel == 8) ? 4 : 8;
+	hitfb_writew(ldr3, HD64461_LDR3);
+	return 0;
+}
+
+static const struct fb_ops hitfb_ops = {
+	.owner		= THIS_MODULE,
+	__FB_DEFAULT_IOMEM_OPS_RDWR,
+	.fb_check_var	= hitfb_check_var,
+	.fb_set_par	= hitfb_set_par,
+	.fb_setcolreg	= hitfb_setcolreg,
+	.fb_blank	= hitfb_blank,
+	.fb_sync	= hitfb_sync,
+	.fb_pan_display = hitfb_pan_display,
+	.fb_fillrect	= hitfb_fillrect,
+	.fb_copyarea	= hitfb_copyarea,
+	.fb_imageblit	= cfb_imageblit,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
+};
+
+static int hitfb_probe(struct platform_device *dev)
+{
+	unsigned short lcdclor, ldr3, ldvndr;
+	struct fb_info *info;
+	int ret;
+
+	if (fb_get_options("hitfb", NULL))
+		return -ENODEV;
+
+	hitfb_fix.mmio_start = HD64461_IO_OFFSET(0x1000);
+	hitfb_fix.mmio_len = 0x1000;
+	hitfb_fix.smem_start = HD64461_IO_OFFSET(0x02000000);
+	hitfb_fix.smem_len = 512 * 1024;
+
+	lcdclor = hitfb_readw(HD64461_LCDCLOR);
+	ldvndr = hitfb_readw(HD64461_LDVNDR);
+	ldr3 = hitfb_readw(HD64461_LDR3);
+
+	switch (ldr3 & 15) {
+	default:
+	case 4:
+		hitfb_var.bits_per_pixel = 8;
+		hitfb_var.xres = lcdclor;
+		break;
+	case 8:
+		hitfb_var.bits_per_pixel = 16;
+		hitfb_var.xres = lcdclor / 2;
+		break;
+	}
+	hitfb_fix.line_length = lcdclor;
+	hitfb_fix.visual = (hitfb_var.bits_per_pixel == 8) ?
+	    FB_VISUAL_PSEUDOCOLOR : FB_VISUAL_TRUECOLOR;
+	hitfb_var.yres = ldvndr + 1;
+	hitfb_var.xres_virtual = hitfb_var.xres;
+	hitfb_var.yres_virtual = hitfb_fix.smem_len / lcdclor;
+	switch (hitfb_var.bits_per_pixel) {
+	case 8:
+		hitfb_var.red.offset = 0;
+		hitfb_var.red.length = 8;
+		hitfb_var.green.offset = 0;
+		hitfb_var.green.length = 8;
+		hitfb_var.blue.offset = 0;
+		hitfb_var.blue.length = 8;
+		hitfb_var.transp.offset = 0;
+		hitfb_var.transp.length = 0;
+		break;
+	case 16:		/* RGB 565 */
+		hitfb_var.red.offset = 11;
+		hitfb_var.red.length = 5;
+		hitfb_var.green.offset = 5;
+		hitfb_var.green.length = 6;
+		hitfb_var.blue.offset = 0;
+		hitfb_var.blue.length = 5;
+		hitfb_var.transp.offset = 0;
+		hitfb_var.transp.length = 0;
+		break;
+	}
+
+	info = framebuffer_alloc(sizeof(u32) * 16, &dev->dev);
+	if (unlikely(!info))
+		return -ENOMEM;
+
+	info->fbops = &hitfb_ops;
+	info->var = hitfb_var;
+	info->fix = hitfb_fix;
+	info->pseudo_palette = info->par;
+	info->flags = FBINFO_HWACCEL_YPAN |
+		FBINFO_HWACCEL_FILLRECT | FBINFO_HWACCEL_COPYAREA;
+
+	info->screen_base = (char __iomem *)(uintptr_t)hitfb_fix.smem_start;
+
+	ret = fb_alloc_cmap(&info->cmap, 256, 0);
+	if (unlikely(ret < 0))
+		goto err_fb;
+
+	ret = register_framebuffer(info);
+	if (unlikely(ret < 0))
+		goto err;
+
+	platform_set_drvdata(dev, info);
+
+	fb_info(info, "%s frame buffer device\n", info->fix.id);
+
+	return 0;
+
+err:
+	fb_dealloc_cmap(&info->cmap);
+err_fb:
+	framebuffer_release(info);
+	return ret;
+}
+
+static void hitfb_remove(struct platform_device *dev)
+{
+	struct fb_info *info = platform_get_drvdata(dev);
+
+	unregister_framebuffer(info);
+	fb_dealloc_cmap(&info->cmap);
+	framebuffer_release(info);
+}
+
+static int hitfb_suspend(struct device *dev)
+{
+	u16 v;
+
+	hitfb_blank(1, NULL);
+	v = hitfb_readw(HD64461_STBCR);
+	v |= HD64461_STBCR_SLCKE_IST;
+	hitfb_writew(v, HD64461_STBCR);
+
+	return 0;
+}
+
+static int hitfb_resume(struct device *dev)
+{
+	u16 v;
+
+	v = hitfb_readw(HD64461_STBCR);
+	v &= ~HD64461_STBCR_SLCKE_OST;
+	msleep(100);
+	v = hitfb_readw(HD64461_STBCR);
+	v &= ~HD64461_STBCR_SLCKE_IST;
+	hitfb_writew(v, HD64461_STBCR);
+	hitfb_blank(0, NULL);
+
+	return 0;
+}
+
+static const struct dev_pm_ops hitfb_dev_pm_ops = {
+	.suspend	= hitfb_suspend,
+	.resume		= hitfb_resume,
+};
+
+static struct platform_driver hitfb_driver = {
+	.probe		= hitfb_probe,
+	.remove		= hitfb_remove,
+	.driver		= {
+		.name	= "hitfb",
+		.pm	= &hitfb_dev_pm_ops,
+	},
+};
+
+static struct platform_device hitfb_device = {
+	.name	= "hitfb",
+	.id	= -1,
+};
+
+static int __init hitfb_init(void)
+{
+	int ret;
+
+	ret = platform_driver_register(&hitfb_driver);
+	if (!ret) {
+		ret = platform_device_register(&hitfb_device);
+		if (ret)
+			platform_driver_unregister(&hitfb_driver);
+	}
+	return ret;
+}
+
+
+static void __exit hitfb_exit(void)
+{
+	platform_device_unregister(&hitfb_device);
+	platform_driver_unregister(&hitfb_driver);
+}
+
+module_init(hitfb_init);
+module_exit(hitfb_exit);
+
+MODULE_LICENSE("GPL");