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, 322 insertions, 0 deletions

diff --git a/drivers/video/fbdev/goldfishfb.c b/drivers/video/fbdev/goldfishfb.c
new file mode 100644
index 000000000..e5d79886e
--- /dev/null
+++ b/drivers/video/fbdev/goldfishfb.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2007 Google, Inc.
+ * Copyright (C) 2012 Intel, Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/dma-mapping.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/mm.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+
+enum {
+	FB_GET_WIDTH        = 0x00,
+	FB_GET_HEIGHT       = 0x04,
+	FB_INT_STATUS       = 0x08,
+	FB_INT_ENABLE       = 0x0c,
+	FB_SET_BASE         = 0x10,
+	FB_SET_ROTATION     = 0x14,
+	FB_SET_BLANK        = 0x18,
+	FB_GET_PHYS_WIDTH   = 0x1c,
+	FB_GET_PHYS_HEIGHT  = 0x20,
+
+	FB_INT_VSYNC             = 1U << 0,
+	FB_INT_BASE_UPDATE_DONE  = 1U << 1
+};
+
+struct goldfish_fb {
+	void __iomem *reg_base;
+	int irq;
+	spinlock_t lock;
+	wait_queue_head_t wait;
+	int base_update_count;
+	int rotation;
+	struct fb_info fb;
+	u32 cmap[16];
+};
+
+static irqreturn_t goldfish_fb_interrupt(int irq, void *dev_id)
+{
+	unsigned long irq_flags;
+	struct goldfish_fb *fb = dev_id;
+	u32 status;
+
+	spin_lock_irqsave(&fb->lock, irq_flags);
+	status = readl(fb->reg_base + FB_INT_STATUS);
+	if (status & FB_INT_BASE_UPDATE_DONE) {
+		fb->base_update_count++;
+		wake_up(&fb->wait);
+	}
+	spin_unlock_irqrestore(&fb->lock, irq_flags);
+	return status ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static inline u32 convert_bitfield(int val, struct fb_bitfield *bf)
+{
+	unsigned int mask = (1 << bf->length) - 1;
+
+	return (val >> (16 - bf->length) & mask) << bf->offset;
+}
+
+static int
+goldfish_fb_setcolreg(unsigned int regno, unsigned int red, unsigned int green,
+		 unsigned int blue, unsigned int transp, struct fb_info *info)
+{
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	if (regno < 16) {
+		fb->cmap[regno] = convert_bitfield(transp, &fb->fb.var.transp) |
+				  convert_bitfield(blue, &fb->fb.var.blue) |
+				  convert_bitfield(green, &fb->fb.var.green) |
+				  convert_bitfield(red, &fb->fb.var.red);
+		return 0;
+	} else {
+		return 1;
+	}
+}
+
+static int goldfish_fb_check_var(struct fb_var_screeninfo *var,
+							struct fb_info *info)
+{
+	if ((var->rotate & 1) != (info->var.rotate & 1)) {
+		if ((var->xres != info->var.yres) ||
+				(var->yres != info->var.xres) ||
+				(var->xres_virtual != info->var.yres) ||
+				(var->yres_virtual > info->var.xres * 2) ||
+				(var->yres_virtual < info->var.xres)) {
+			return -EINVAL;
+		}
+	} else {
+		if ((var->xres != info->var.xres) ||
+		   (var->yres != info->var.yres) ||
+		   (var->xres_virtual != info->var.xres) ||
+		   (var->yres_virtual > info->var.yres * 2) ||
+		   (var->yres_virtual < info->var.yres)) {
+			return -EINVAL;
+		}
+	}
+	if ((var->xoffset != info->var.xoffset) ||
+			(var->bits_per_pixel != info->var.bits_per_pixel) ||
+			(var->grayscale != info->var.grayscale)) {
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int goldfish_fb_set_par(struct fb_info *info)
+{
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	if (fb->rotation != fb->fb.var.rotate) {
+		info->fix.line_length = info->var.xres * 2;
+		fb->rotation = fb->fb.var.rotate;
+		writel(fb->rotation, fb->reg_base + FB_SET_ROTATION);
+	}
+	return 0;
+}
+
+
+static int goldfish_fb_pan_display(struct fb_var_screeninfo *var,
+							struct fb_info *info)
+{
+	unsigned long irq_flags;
+	int base_update_count;
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	spin_lock_irqsave(&fb->lock, irq_flags);
+	base_update_count = fb->base_update_count;
+	writel(fb->fb.fix.smem_start + fb->fb.var.xres * 2 * var->yoffset,
+						fb->reg_base + FB_SET_BASE);
+	spin_unlock_irqrestore(&fb->lock, irq_flags);
+	if (!wait_event_timeout(fb->wait,
+				fb->base_update_count != base_update_count,
+				HZ / 15)) {
+		pr_err("%s: timeout waiting for base update\n", __func__);
+		return -ETIMEDOUT;
+	}
+	return 0;
+}
+
+static int goldfish_fb_blank(int blank, struct fb_info *info)
+{
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	switch (blank) {
+	case FB_BLANK_NORMAL:
+		writel(1, fb->reg_base + FB_SET_BLANK);
+		break;
+	case FB_BLANK_UNBLANK:
+		writel(0, fb->reg_base + FB_SET_BLANK);
+		break;
+	}
+	return 0;
+}
+
+static const struct fb_ops goldfish_fb_ops = {
+	.owner          = THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_check_var   = goldfish_fb_check_var,
+	.fb_set_par     = goldfish_fb_set_par,
+	.fb_setcolreg   = goldfish_fb_setcolreg,
+	.fb_pan_display = goldfish_fb_pan_display,
+	.fb_blank	= goldfish_fb_blank,
+};
+
+
+static int goldfish_fb_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct goldfish_fb *fb;
+	size_t framesize;
+	u32 width, height;
+	dma_addr_t fbpaddr;
+
+	fb = kzalloc_obj(*fb);
+	if (fb == NULL) {
+		ret = -ENOMEM;
+		goto err_fb_alloc_failed;
+	}
+	spin_lock_init(&fb->lock);
+	init_waitqueue_head(&fb->wait);
+	platform_set_drvdata(pdev, fb);
+
+	fb->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fb->reg_base)) {
+		ret = PTR_ERR(fb->reg_base);
+		goto err_no_io_base;
+	}
+
+	fb->irq = platform_get_irq(pdev, 0);
+	if (fb->irq < 0) {
+		ret = fb->irq;
+		goto err_no_irq;
+	}
+
+	width = readl(fb->reg_base + FB_GET_WIDTH);
+	height = readl(fb->reg_base + FB_GET_HEIGHT);
+
+	fb->fb.fbops		= &goldfish_fb_ops;
+	fb->fb.pseudo_palette	= fb->cmap;
+	fb->fb.fix.type		= FB_TYPE_PACKED_PIXELS;
+	fb->fb.fix.visual = FB_VISUAL_TRUECOLOR;
+	fb->fb.fix.line_length = width * 2;
+	fb->fb.fix.accel	= FB_ACCEL_NONE;
+	fb->fb.fix.ypanstep = 1;
+
+	fb->fb.var.xres		= width;
+	fb->fb.var.yres		= height;
+	fb->fb.var.xres_virtual	= width;
+	fb->fb.var.yres_virtual	= height * 2;
+	fb->fb.var.bits_per_pixel = 16;
+	fb->fb.var.activate	= FB_ACTIVATE_NOW;
+	fb->fb.var.height	= readl(fb->reg_base + FB_GET_PHYS_HEIGHT);
+	fb->fb.var.width	= readl(fb->reg_base + FB_GET_PHYS_WIDTH);
+	fb->fb.var.pixclock	= 0;
+
+	fb->fb.var.red.offset = 11;
+	fb->fb.var.red.length = 5;
+	fb->fb.var.green.offset = 5;
+	fb->fb.var.green.length = 6;
+	fb->fb.var.blue.offset = 0;
+	fb->fb.var.blue.length = 5;
+
+	framesize = width * height * 2 * 2;
+	fb->fb.screen_base = (char __force __iomem *)dma_alloc_coherent(
+						&pdev->dev, framesize,
+						&fbpaddr, GFP_KERNEL);
+	pr_debug("allocating frame buffer %d * %d, got %p\n",
+					width, height, fb->fb.screen_base);
+	if (fb->fb.screen_base == NULL) {
+		ret = -ENOMEM;
+		goto err_alloc_screen_base_failed;
+	}
+	fb->fb.fix.smem_start = fbpaddr;
+	fb->fb.fix.smem_len = framesize;
+
+	ret = fb_set_var(&fb->fb, &fb->fb.var);
+	if (ret)
+		goto err_fb_set_var_failed;
+
+	ret = request_irq(fb->irq, goldfish_fb_interrupt, IRQF_SHARED,
+							pdev->name, fb);
+	if (ret)
+		goto err_request_irq_failed;
+
+	writel(FB_INT_BASE_UPDATE_DONE, fb->reg_base + FB_INT_ENABLE);
+	ret = goldfish_fb_pan_display(&fb->fb.var, &fb->fb); /* updates base */
+	if (ret)
+		goto err_pan_display_failed;
+
+	ret = register_framebuffer(&fb->fb);
+	if (ret)
+		goto err_register_framebuffer_failed;
+	return 0;
+
+err_register_framebuffer_failed:
+err_pan_display_failed:
+	free_irq(fb->irq, fb);
+err_request_irq_failed:
+err_fb_set_var_failed:
+	dma_free_coherent(&pdev->dev, framesize,
+				(void *)fb->fb.screen_base,
+				fb->fb.fix.smem_start);
+err_alloc_screen_base_failed:
+err_no_irq:
+err_no_io_base:
+	kfree(fb);
+err_fb_alloc_failed:
+	return ret;
+}
+
+static void goldfish_fb_remove(struct platform_device *pdev)
+{
+	size_t framesize;
+	struct goldfish_fb *fb = platform_get_drvdata(pdev);
+
+	framesize = fb->fb.var.xres_virtual * fb->fb.var.yres_virtual * 2;
+	unregister_framebuffer(&fb->fb);
+	free_irq(fb->irq, fb);
+
+	dma_free_coherent(&pdev->dev, framesize, (void *)fb->fb.screen_base,
+						fb->fb.fix.smem_start);
+	kfree(fb);
+}
+
+static const struct of_device_id goldfish_fb_of_match[] = {
+	{ .compatible = "google,goldfish-fb", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, goldfish_fb_of_match);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id goldfish_fb_acpi_match[] = {
+	{ "GFSH0004", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, goldfish_fb_acpi_match);
+#endif
+
+static struct platform_driver goldfish_fb_driver = {
+	.probe		= goldfish_fb_probe,
+	.remove		= goldfish_fb_remove,
+	.driver = {
+		.name = "goldfish_fb",
+		.of_match_table = goldfish_fb_of_match,
+		.acpi_match_table = ACPI_PTR(goldfish_fb_acpi_match),
+	}
+};
+
+module_platform_driver(goldfish_fb_driver);
+
+MODULE_DESCRIPTION("Goldfish Virtual Platform Framebuffer driver");
+MODULE_LICENSE("GPL v2");