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, 407 insertions, 0 deletions

diff --git a/drivers/video/fbdev/wm8505fb.c b/drivers/video/fbdev/wm8505fb.c
new file mode 100644
index 000000000..5caf74ca9
--- /dev/null
+++ b/drivers/video/fbdev/wm8505fb.c
@@ -0,0 +1,407 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  WonderMedia WM8505 Frame Buffer device driver
+ *
+ *  Copyright (C) 2010 Ed Spiridonov <edo.rus@gmail.com>
+ *    Based on vt8500lcdfb.c
+ */
+
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/fb.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/memblock.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/wait.h>
+#include <video/of_display_timing.h>
+
+#include "wm8505fb_regs.h"
+#include "wmt_ge_rops.h"
+
+#define DRIVER_NAME "wm8505-fb"
+
+#define to_wm8505fb_info(__info) container_of(__info, \
+						struct wm8505fb_info, fb)
+struct wm8505fb_info {
+	struct fb_info		fb;
+	void __iomem		*regbase;
+	unsigned int		contrast;
+};
+
+
+static int wm8505fb_init_hw(struct fb_info *info)
+{
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+
+	int i;
+
+	/* I know the purpose only of few registers, so clear unknown */
+	for (i = 0; i < 0x200; i += 4)
+		writel(0, fbi->regbase + i);
+
+	/* Set frame buffer address */
+	writel(fbi->fb.fix.smem_start, fbi->regbase + WMT_GOVR_FBADDR);
+	writel(fbi->fb.fix.smem_start, fbi->regbase + WMT_GOVR_FBADDR1);
+
+	/*
+	 * Set in-memory picture format to RGB
+	 * 0x31C sets the correct color mode (RGB565) for WM8650
+	 * Bit 8+9 (0x300) are ignored on WM8505 as reserved
+	 */
+	writel(0x31c,		       fbi->regbase + WMT_GOVR_COLORSPACE);
+	writel(1,		       fbi->regbase + WMT_GOVR_COLORSPACE1);
+
+	/* Virtual buffer size */
+	writel(info->var.xres,	       fbi->regbase + WMT_GOVR_XRES);
+	writel(info->var.xres_virtual, fbi->regbase + WMT_GOVR_XRES_VIRTUAL);
+
+	/* black magic ;) */
+	writel(0xf,		       fbi->regbase + WMT_GOVR_FHI);
+	writel(4,		       fbi->regbase + WMT_GOVR_DVO_SET);
+	writel(1,		       fbi->regbase + WMT_GOVR_MIF_ENABLE);
+	writel(1,		       fbi->regbase + WMT_GOVR_REG_UPDATE);
+
+	return 0;
+}
+
+static int wm8505fb_set_timing(struct fb_info *info)
+{
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+
+	int h_start = info->var.left_margin;
+	int h_end = h_start + info->var.xres;
+	int h_all = h_end + info->var.right_margin;
+	int h_sync = info->var.hsync_len;
+
+	int v_start = info->var.upper_margin;
+	int v_end = v_start + info->var.yres;
+	int v_all = v_end + info->var.lower_margin;
+	int v_sync = info->var.vsync_len;
+
+	writel(0, fbi->regbase + WMT_GOVR_TG);
+
+	writel(h_start, fbi->regbase + WMT_GOVR_TIMING_H_START);
+	writel(h_end,   fbi->regbase + WMT_GOVR_TIMING_H_END);
+	writel(h_all,   fbi->regbase + WMT_GOVR_TIMING_H_ALL);
+	writel(h_sync,  fbi->regbase + WMT_GOVR_TIMING_H_SYNC);
+
+	writel(v_start, fbi->regbase + WMT_GOVR_TIMING_V_START);
+	writel(v_end,   fbi->regbase + WMT_GOVR_TIMING_V_END);
+	writel(v_all,   fbi->regbase + WMT_GOVR_TIMING_V_ALL);
+	writel(v_sync,  fbi->regbase + WMT_GOVR_TIMING_V_SYNC);
+
+	writel(1, fbi->regbase + WMT_GOVR_TG);
+
+	return 0;
+}
+
+
+static int wm8505fb_set_par(struct fb_info *info)
+{
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+
+	if (!fbi)
+		return -EINVAL;
+
+	if (info->var.bits_per_pixel == 32) {
+		info->var.red.offset = 16;
+		info->var.red.length = 8;
+		info->var.red.msb_right = 0;
+		info->var.green.offset = 8;
+		info->var.green.length = 8;
+		info->var.green.msb_right = 0;
+		info->var.blue.offset = 0;
+		info->var.blue.length = 8;
+		info->var.blue.msb_right = 0;
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+		info->fix.line_length = info->var.xres_virtual << 2;
+	} else if (info->var.bits_per_pixel == 16) {
+		info->var.red.offset = 11;
+		info->var.red.length = 5;
+		info->var.red.msb_right = 0;
+		info->var.green.offset = 5;
+		info->var.green.length = 6;
+		info->var.green.msb_right = 0;
+		info->var.blue.offset = 0;
+		info->var.blue.length = 5;
+		info->var.blue.msb_right = 0;
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+		info->fix.line_length = info->var.xres_virtual << 1;
+	}
+
+	wm8505fb_set_timing(info);
+
+	writel(fbi->contrast<<16 | fbi->contrast<<8 | fbi->contrast,
+		fbi->regbase + WMT_GOVR_CONTRAST);
+
+	return 0;
+}
+
+static ssize_t contrast_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct fb_info *info = dev_get_drvdata(dev);
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+
+	return sprintf(buf, "%u\n", fbi->contrast);
+}
+
+static ssize_t contrast_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct fb_info *info = dev_get_drvdata(dev);
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+	unsigned long tmp;
+
+	if (kstrtoul(buf, 10, &tmp) || (tmp > 0xff))
+		return -EINVAL;
+	fbi->contrast = tmp;
+
+	wm8505fb_set_par(info);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(contrast);
+
+static struct attribute *wm8505fb_attrs[] = {
+	&dev_attr_contrast.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(wm8505fb);
+
+static inline u_int chan_to_field(u_int chan, struct fb_bitfield *bf)
+{
+	chan &= 0xffff;
+	chan >>= 16 - bf->length;
+	return chan << bf->offset;
+}
+
+static int wm8505fb_setcolreg(unsigned regno, unsigned red, unsigned green,
+			   unsigned blue, unsigned transp,
+			   struct fb_info *info) {
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+	int ret = 1;
+	unsigned int val;
+	if (regno >= 256)
+		return -EINVAL;
+
+	if (info->var.grayscale)
+		red = green = blue =
+			(19595 * red + 38470 * green + 7471 * blue) >> 16;
+
+	switch (fbi->fb.fix.visual) {
+	case FB_VISUAL_TRUECOLOR:
+		if (regno < 16) {
+			u32 *pal = info->pseudo_palette;
+
+			val  = chan_to_field(red, &fbi->fb.var.red);
+			val |= chan_to_field(green, &fbi->fb.var.green);
+			val |= chan_to_field(blue, &fbi->fb.var.blue);
+
+			pal[regno] = val;
+			ret = 0;
+		}
+		break;
+	}
+
+	return ret;
+}
+
+static int wm8505fb_pan_display(struct fb_var_screeninfo *var,
+				struct fb_info *info)
+{
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+
+	writel(var->xoffset, fbi->regbase + WMT_GOVR_XPAN);
+	writel(var->yoffset, fbi->regbase + WMT_GOVR_YPAN);
+	return 0;
+}
+
+static int wm8505fb_blank(int blank, struct fb_info *info)
+{
+	struct wm8505fb_info *fbi = to_wm8505fb_info(info);
+
+	switch (blank) {
+	case FB_BLANK_UNBLANK:
+		wm8505fb_set_timing(info);
+		break;
+	default:
+		writel(0,  fbi->regbase + WMT_GOVR_TIMING_V_SYNC);
+		break;
+	}
+
+	return 0;
+}
+
+static const struct fb_ops wm8505fb_ops = {
+	.owner		= THIS_MODULE,
+	__FB_DEFAULT_DMAMEM_OPS_RDWR,
+	.fb_set_par	= wm8505fb_set_par,
+	.fb_setcolreg	= wm8505fb_setcolreg,
+	.fb_fillrect	= wmt_ge_fillrect,
+	.fb_copyarea	= wmt_ge_copyarea,
+	.fb_imageblit	= sys_imageblit,
+	.fb_sync	= wmt_ge_sync,
+	.fb_pan_display	= wm8505fb_pan_display,
+	.fb_blank	= wm8505fb_blank,
+	__FB_DEFAULT_IOMEM_OPS_MMAP,
+};
+
+static int wm8505fb_probe(struct platform_device *pdev)
+{
+	struct wm8505fb_info	*fbi;
+	struct display_timings *disp_timing;
+	void			*addr;
+	int ret;
+
+	struct fb_videomode	mode;
+	u32			bpp;
+	dma_addr_t fb_mem_phys;
+	unsigned long fb_mem_len;
+	void *fb_mem_virt;
+
+	fbi = devm_kzalloc(&pdev->dev, sizeof(struct wm8505fb_info) +
+			sizeof(u32) * 16, GFP_KERNEL);
+	if (!fbi)
+		return -ENOMEM;
+
+	strcpy(fbi->fb.fix.id, DRIVER_NAME);
+
+	fbi->fb.fix.type	= FB_TYPE_PACKED_PIXELS;
+	fbi->fb.fix.xpanstep	= 1;
+	fbi->fb.fix.ypanstep	= 1;
+	fbi->fb.fix.ywrapstep	= 0;
+	fbi->fb.fix.accel	= FB_ACCEL_NONE;
+
+	fbi->fb.fbops		= &wm8505fb_ops;
+	fbi->fb.flags		= FBINFO_HWACCEL_COPYAREA
+				| FBINFO_HWACCEL_FILLRECT
+				| FBINFO_HWACCEL_XPAN
+				| FBINFO_HWACCEL_YPAN
+				| FBINFO_VIRTFB
+				| FBINFO_PARTIAL_PAN_OK;
+	fbi->fb.node		= -1;
+
+	addr = fbi;
+	addr = addr + sizeof(struct wm8505fb_info);
+	fbi->fb.pseudo_palette	= addr;
+
+	fbi->regbase = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fbi->regbase))
+		return PTR_ERR(fbi->regbase);
+
+	disp_timing = of_get_display_timings(pdev->dev.of_node);
+	if (!disp_timing)
+		return -EINVAL;
+
+	ret = of_get_fb_videomode(pdev->dev.of_node, &mode, OF_USE_NATIVE_MODE);
+	if (ret)
+		return ret;
+
+	ret = of_property_read_u32(pdev->dev.of_node, "bits-per-pixel", &bpp);
+	if (ret)
+		return ret;
+
+	fb_videomode_to_var(&fbi->fb.var, &mode);
+
+	fbi->fb.var.nonstd		= 0;
+	fbi->fb.var.activate		= FB_ACTIVATE_NOW;
+
+	fbi->fb.var.height		= -1;
+	fbi->fb.var.width		= -1;
+
+	/* try allocating the framebuffer */
+	fb_mem_len = mode.xres * mode.yres * 2 * (bpp / 8);
+	fb_mem_virt = dmam_alloc_coherent(&pdev->dev, fb_mem_len, &fb_mem_phys,
+				GFP_KERNEL);
+	if (!fb_mem_virt) {
+		pr_err("%s: Failed to allocate framebuffer\n", __func__);
+		return -ENOMEM;
+	}
+
+	fbi->fb.var.xres_virtual	= mode.xres;
+	fbi->fb.var.yres_virtual	= mode.yres * 2;
+	fbi->fb.var.bits_per_pixel	= bpp;
+
+	fbi->fb.fix.smem_start		= fb_mem_phys;
+	fbi->fb.fix.smem_len		= fb_mem_len;
+	fbi->fb.screen_buffer		= fb_mem_virt;
+	fbi->fb.screen_size		= fb_mem_len;
+
+	fbi->contrast = 0x10;
+	ret = wm8505fb_set_par(&fbi->fb);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to set parameters\n");
+		return ret;
+	}
+
+	if (fb_alloc_cmap(&fbi->fb.cmap, 256, 0) < 0) {
+		dev_err(&pdev->dev, "Failed to allocate color map\n");
+		return -ENOMEM;
+	}
+
+	wm8505fb_init_hw(&fbi->fb);
+
+	platform_set_drvdata(pdev, fbi);
+
+	ret = register_framebuffer(&fbi->fb);
+	if (ret < 0) {
+		dev_err(&pdev->dev,
+			"Failed to register framebuffer device: %d\n", ret);
+		if (fbi->fb.cmap.len)
+			fb_dealloc_cmap(&fbi->fb.cmap);
+		return ret;
+	}
+
+	fb_info(&fbi->fb, "%s frame buffer at 0x%lx-0x%lx\n",
+		fbi->fb.fix.id, fbi->fb.fix.smem_start,
+		fbi->fb.fix.smem_start + fbi->fb.fix.smem_len - 1);
+
+	return 0;
+}
+
+static void wm8505fb_remove(struct platform_device *pdev)
+{
+	struct wm8505fb_info *fbi = platform_get_drvdata(pdev);
+
+	unregister_framebuffer(&fbi->fb);
+
+	writel(0, fbi->regbase);
+
+	if (fbi->fb.cmap.len)
+		fb_dealloc_cmap(&fbi->fb.cmap);
+}
+
+static const struct of_device_id wmt_dt_ids[] = {
+	{ .compatible = "wm,wm8505-fb", },
+	{}
+};
+
+static struct platform_driver wm8505fb_driver = {
+	.probe		= wm8505fb_probe,
+	.remove		= wm8505fb_remove,
+	.driver		= {
+		.name	= DRIVER_NAME,
+		.of_match_table = wmt_dt_ids,
+		.dev_groups	= wm8505fb_groups,
+	},
+};
+
+module_platform_driver(wm8505fb_driver);
+
+MODULE_AUTHOR("Ed Spiridonov <edo.rus@gmail.com>");
+MODULE_DESCRIPTION("Framebuffer driver for WMT WM8505");
+MODULE_DEVICE_TABLE(of, wmt_dt_ids);