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, 483 insertions, 0 deletions

diff --git a/drivers/video/fbdev/cg3.c b/drivers/video/fbdev/cg3.c
new file mode 100644
index 000000000..a58a48301
--- /dev/null
+++ b/drivers/video/fbdev/cg3.c
@@ -0,0 +1,483 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* cg3.c: CGTHREE frame buffer driver
+ *
+ * Copyright (C) 2003, 2006 David S. Miller (davem@davemloft.net)
+ * Copyright (C) 1996,1998 Jakub Jelinek (jj@ultra.linux.cz)
+ * Copyright (C) 1996 Miguel de Icaza (miguel@nuclecu.unam.mx)
+ * Copyright (C) 1997 Eddie C. Dost (ecd@skynet.be)
+ *
+ * Driver layout based loosely on tgafb.c, see that file for credits.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/fb.h>
+#include <linux/mm.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#include <asm/io.h>
+#include <asm/fbio.h>
+
+#include "sbuslib.h"
+
+/*
+ * Local functions.
+ */
+
+static int cg3_setcolreg(unsigned, unsigned, unsigned, unsigned,
+			 unsigned, struct fb_info *);
+static int cg3_blank(int, struct fb_info *);
+
+static int cg3_sbusfb_mmap(struct fb_info *info, struct vm_area_struct *vma);
+static int cg3_sbusfb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg);
+
+/*
+ *  Frame buffer operations
+ */
+
+static const struct fb_ops cg3_ops = {
+	.owner			= THIS_MODULE,
+	FB_DEFAULT_SBUS_OPS(cg3),
+	.fb_setcolreg		= cg3_setcolreg,
+	.fb_blank		= cg3_blank,
+};
+
+
+/* Control Register Constants */
+#define CG3_CR_ENABLE_INTS      0x80
+#define CG3_CR_ENABLE_VIDEO     0x40
+#define CG3_CR_ENABLE_TIMING    0x20
+#define CG3_CR_ENABLE_CURCMP    0x10
+#define CG3_CR_XTAL_MASK        0x0c
+#define CG3_CR_DIVISOR_MASK     0x03
+
+/* Status Register Constants */
+#define CG3_SR_PENDING_INT      0x80
+#define CG3_SR_RES_MASK         0x70
+#define CG3_SR_1152_900_76_A    0x40
+#define CG3_SR_1152_900_76_B    0x60
+#define CG3_SR_ID_MASK          0x0f
+#define CG3_SR_ID_COLOR         0x01
+#define CG3_SR_ID_MONO          0x02
+#define CG3_SR_ID_MONO_ECL      0x03
+
+enum cg3_type {
+	CG3_AT_66HZ = 0,
+	CG3_AT_76HZ,
+	CG3_RDI
+};
+
+struct bt_regs {
+	u32 addr;
+	u32 color_map;
+	u32 control;
+	u32 cursor;
+};
+
+struct cg3_regs {
+	struct bt_regs	cmap;
+	u8	control;
+	u8	status;
+	u8	cursor_start;
+	u8	cursor_end;
+	u8	h_blank_start;
+	u8	h_blank_end;
+	u8	h_sync_start;
+	u8	h_sync_end;
+	u8	comp_sync_end;
+	u8	v_blank_start_high;
+	u8	v_blank_start_low;
+	u8	v_blank_end;
+	u8	v_sync_start;
+	u8	v_sync_end;
+	u8	xfer_holdoff_start;
+	u8	xfer_holdoff_end;
+};
+
+/* Offset of interesting structures in the OBIO space */
+#define CG3_REGS_OFFSET	     0x400000UL
+#define CG3_RAM_OFFSET	     0x800000UL
+
+struct cg3_par {
+	spinlock_t		lock;
+	struct cg3_regs		__iomem *regs;
+	u32			sw_cmap[((256 * 3) + 3) / 4];
+
+	u32			flags;
+#define CG3_FLAG_BLANKED	0x00000001
+#define CG3_FLAG_RDI		0x00000002
+
+	unsigned long		which_io;
+};
+
+/**
+ *      cg3_setcolreg - Optional function. Sets a color register.
+ *      @regno: boolean, 0 copy local, 1 get_user() function
+ *      @red: frame buffer colormap structure
+ *      @green: The green value which can be up to 16 bits wide
+ *      @blue:  The blue value which can be up to 16 bits wide.
+ *      @transp: If supported the alpha value which can be up to 16 bits wide.
+ *      @info: frame buffer info structure
+ *
+ * The cg3 palette is loaded with 4 color values at each time
+ * so you end up with: (rgb)(r), (gb)(rg), (b)(rgb), and so on.
+ * We keep a sw copy of the hw cmap to assist us in this esoteric
+ * loading procedure.
+ */
+static int cg3_setcolreg(unsigned regno,
+			 unsigned red, unsigned green, unsigned blue,
+			 unsigned transp, struct fb_info *info)
+{
+	struct cg3_par *par = (struct cg3_par *) info->par;
+	struct bt_regs __iomem *bt = &par->regs->cmap;
+	unsigned long flags;
+	u32 *p32;
+	u8 *p8;
+	int count;
+
+	if (regno >= 256)
+		return 1;
+
+	red >>= 8;
+	green >>= 8;
+	blue >>= 8;
+
+	spin_lock_irqsave(&par->lock, flags);
+
+	p8 = (u8 *)par->sw_cmap + (regno * 3);
+	p8[0] = red;
+	p8[1] = green;
+	p8[2] = blue;
+
+#define D4M3(x) ((((x)>>2)<<1) + ((x)>>2))      /* (x/4)*3 */
+#define D4M4(x) ((x)&~0x3)                      /* (x/4)*4 */
+
+	count = 3;
+	p32 = &par->sw_cmap[D4M3(regno)];
+	sbus_writel(D4M4(regno), &bt->addr);
+	while (count--)
+		sbus_writel(*p32++, &bt->color_map);
+
+#undef D4M3
+#undef D4M4
+
+	spin_unlock_irqrestore(&par->lock, flags);
+
+	return 0;
+}
+
+/**
+ *      cg3_blank - Optional function.  Blanks the display.
+ *      @blank: the blank mode we want.
+ *      @info: frame buffer structure that represents a single frame buffer
+ */
+static int cg3_blank(int blank, struct fb_info *info)
+{
+	struct cg3_par *par = (struct cg3_par *) info->par;
+	struct cg3_regs __iomem *regs = par->regs;
+	unsigned long flags;
+	u8 val;
+
+	spin_lock_irqsave(&par->lock, flags);
+
+	switch (blank) {
+	case FB_BLANK_UNBLANK: /* Unblanking */
+		val = sbus_readb(&regs->control);
+		val |= CG3_CR_ENABLE_VIDEO;
+		sbus_writeb(val, &regs->control);
+		par->flags &= ~CG3_FLAG_BLANKED;
+		break;
+
+	case FB_BLANK_NORMAL: /* Normal blanking */
+	case FB_BLANK_VSYNC_SUSPEND: /* VESA blank (vsync off) */
+	case FB_BLANK_HSYNC_SUSPEND: /* VESA blank (hsync off) */
+	case FB_BLANK_POWERDOWN: /* Poweroff */
+		val = sbus_readb(&regs->control);
+		val &= ~CG3_CR_ENABLE_VIDEO;
+		sbus_writeb(val, &regs->control);
+		par->flags |= CG3_FLAG_BLANKED;
+		break;
+	}
+
+	spin_unlock_irqrestore(&par->lock, flags);
+
+	return 0;
+}
+
+static const struct sbus_mmap_map cg3_mmap_map[] = {
+	{
+		.voff	= CG3_MMAP_OFFSET,
+		.poff	= CG3_RAM_OFFSET,
+		.size	= SBUS_MMAP_FBSIZE(1)
+	},
+	{ .size = 0 }
+};
+
+static int cg3_sbusfb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct cg3_par *par = (struct cg3_par *)info->par;
+
+	return sbusfb_mmap_helper(cg3_mmap_map,
+				  info->fix.smem_start, info->fix.smem_len,
+				  par->which_io,
+				  vma);
+}
+
+static int cg3_sbusfb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg)
+{
+	return sbusfb_ioctl_helper(cmd, arg, info,
+				   FBTYPE_SUN3COLOR, 8, info->fix.smem_len);
+}
+
+/*
+ *  Initialisation
+ */
+
+static void cg3_init_fix(struct fb_info *info, int linebytes,
+			 struct device_node *dp)
+{
+	snprintf(info->fix.id, sizeof(info->fix.id), "%pOFn", dp);
+
+	info->fix.type = FB_TYPE_PACKED_PIXELS;
+	info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
+
+	info->fix.line_length = linebytes;
+
+	info->fix.accel = FB_ACCEL_SUN_CGTHREE;
+}
+
+static void cg3_rdi_maybe_fixup_var(struct fb_var_screeninfo *var,
+				    struct device_node *dp)
+{
+	const char *params;
+	char *p;
+	int ww, hh;
+
+	params = of_get_property(dp, "params", NULL);
+	if (params) {
+		ww = simple_strtoul(params, &p, 10);
+		if (ww && *p == 'x') {
+			hh = simple_strtoul(p + 1, &p, 10);
+			if (hh && *p == '-') {
+				if (var->xres != ww ||
+				    var->yres != hh) {
+					var->xres = var->xres_virtual = ww;
+					var->yres = var->yres_virtual = hh;
+				}
+			}
+		}
+	}
+}
+
+static u8 cg3regvals_66hz[] = {	/* 1152 x 900, 66 Hz */
+	0x14, 0xbb,	0x15, 0x2b,	0x16, 0x04,	0x17, 0x14,
+	0x18, 0xae,	0x19, 0x03,	0x1a, 0xa8,	0x1b, 0x24,
+	0x1c, 0x01,	0x1d, 0x05,	0x1e, 0xff,	0x1f, 0x01,
+	0x10, 0x20,	0
+};
+
+static u8 cg3regvals_76hz[] = {	/* 1152 x 900, 76 Hz */
+	0x14, 0xb7,	0x15, 0x27,	0x16, 0x03,	0x17, 0x0f,
+	0x18, 0xae,	0x19, 0x03,	0x1a, 0xae,	0x1b, 0x2a,
+	0x1c, 0x01,	0x1d, 0x09,	0x1e, 0xff,	0x1f, 0x01,
+	0x10, 0x24,	0
+};
+
+static u8 cg3regvals_rdi[] = {	/* 640 x 480, cgRDI */
+	0x14, 0x70,	0x15, 0x20,	0x16, 0x08,	0x17, 0x10,
+	0x18, 0x06,	0x19, 0x02,	0x1a, 0x31,	0x1b, 0x51,
+	0x1c, 0x06,	0x1d, 0x0c,	0x1e, 0xff,	0x1f, 0x01,
+	0x10, 0x22,	0
+};
+
+static u8 *cg3_regvals[] = {
+	cg3regvals_66hz, cg3regvals_76hz, cg3regvals_rdi
+};
+
+static u_char cg3_dacvals[] = {
+	4, 0xff,	5, 0x00,	6, 0x70,	7, 0x00,	0
+};
+
+static int cg3_do_default_mode(struct cg3_par *par)
+{
+	enum cg3_type type;
+	u8 *p;
+
+	if (par->flags & CG3_FLAG_RDI)
+		type = CG3_RDI;
+	else {
+		u8 status = sbus_readb(&par->regs->status), mon;
+		if ((status & CG3_SR_ID_MASK) == CG3_SR_ID_COLOR) {
+			mon = status & CG3_SR_RES_MASK;
+			if (mon == CG3_SR_1152_900_76_A ||
+			    mon == CG3_SR_1152_900_76_B)
+				type = CG3_AT_76HZ;
+			else
+				type = CG3_AT_66HZ;
+		} else {
+			printk(KERN_ERR "cgthree: can't handle SR %02x\n",
+			       status);
+			return -EINVAL;
+		}
+	}
+
+	for (p = cg3_regvals[type]; *p; p += 2) {
+		u8 __iomem *regp = &((u8 __iomem *)par->regs)[p[0]];
+		sbus_writeb(p[1], regp);
+	}
+	for (p = cg3_dacvals; *p; p += 2) {
+		u8 __iomem *regp;
+
+		regp = (u8 __iomem *)&par->regs->cmap.addr;
+		sbus_writeb(p[0], regp);
+		regp = (u8 __iomem *)&par->regs->cmap.control;
+		sbus_writeb(p[1], regp);
+	}
+	return 0;
+}
+
+static int cg3_probe(struct platform_device *op)
+{
+	struct device_node *dp = op->dev.of_node;
+	struct fb_info *info;
+	struct cg3_par *par;
+	int linebytes, err;
+
+	info = framebuffer_alloc(sizeof(struct cg3_par), &op->dev);
+
+	err = -ENOMEM;
+	if (!info)
+		goto out_err;
+	par = info->par;
+
+	spin_lock_init(&par->lock);
+
+	info->fix.smem_start = op->resource[0].start;
+	par->which_io = op->resource[0].flags & IORESOURCE_BITS;
+
+	sbusfb_fill_var(&info->var, dp, 8);
+	info->var.red.length = 8;
+	info->var.green.length = 8;
+	info->var.blue.length = 8;
+	if (of_node_name_eq(dp, "cgRDI"))
+		par->flags |= CG3_FLAG_RDI;
+	if (par->flags & CG3_FLAG_RDI)
+		cg3_rdi_maybe_fixup_var(&info->var, dp);
+
+	linebytes = of_getintprop_default(dp, "linebytes",
+					  info->var.xres);
+	info->fix.smem_len = PAGE_ALIGN(linebytes * info->var.yres);
+
+	par->regs = of_ioremap(&op->resource[0], CG3_REGS_OFFSET,
+			       sizeof(struct cg3_regs), "cg3 regs");
+	if (!par->regs)
+		goto out_release_fb;
+
+	info->fbops = &cg3_ops;
+	info->screen_base = of_ioremap(&op->resource[0], CG3_RAM_OFFSET,
+				       info->fix.smem_len, "cg3 ram");
+	if (!info->screen_base)
+		goto out_unmap_regs;
+
+	cg3_blank(FB_BLANK_UNBLANK, info);
+
+	if (!of_property_present(dp, "width")) {
+		err = cg3_do_default_mode(par);
+		if (err)
+			goto out_unmap_screen;
+	}
+
+	err = fb_alloc_cmap(&info->cmap, 256, 0);
+	if (err)
+		goto out_unmap_screen;
+
+	fb_set_cmap(&info->cmap, info);
+
+	cg3_init_fix(info, linebytes, dp);
+
+	err = register_framebuffer(info);
+	if (err < 0)
+		goto out_dealloc_cmap;
+
+	dev_set_drvdata(&op->dev, info);
+
+	printk(KERN_INFO "%pOF: cg3 at %lx:%lx\n",
+	       dp, par->which_io, info->fix.smem_start);
+
+	return 0;
+
+out_dealloc_cmap:
+	fb_dealloc_cmap(&info->cmap);
+
+out_unmap_screen:
+	of_iounmap(&op->resource[0], info->screen_base, info->fix.smem_len);
+
+out_unmap_regs:
+	of_iounmap(&op->resource[0], par->regs, sizeof(struct cg3_regs));
+
+out_release_fb:
+	framebuffer_release(info);
+
+out_err:
+	return err;
+}
+
+static void cg3_remove(struct platform_device *op)
+{
+	struct fb_info *info = dev_get_drvdata(&op->dev);
+	struct cg3_par *par = info->par;
+
+	unregister_framebuffer(info);
+	fb_dealloc_cmap(&info->cmap);
+
+	of_iounmap(&op->resource[0], par->regs, sizeof(struct cg3_regs));
+	of_iounmap(&op->resource[0], info->screen_base, info->fix.smem_len);
+
+	framebuffer_release(info);
+}
+
+static const struct of_device_id cg3_match[] = {
+	{
+		.name = "cgthree",
+	},
+	{
+		.name = "cgRDI",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, cg3_match);
+
+static struct platform_driver cg3_driver = {
+	.driver = {
+		.name = "cg3",
+		.of_match_table = cg3_match,
+	},
+	.probe		= cg3_probe,
+	.remove		= cg3_remove,
+};
+
+static int __init cg3_init(void)
+{
+	if (fb_get_options("cg3fb", NULL))
+		return -ENODEV;
+
+	return platform_driver_register(&cg3_driver);
+}
+
+static void __exit cg3_exit(void)
+{
+	platform_driver_unregister(&cg3_driver);
+}
+
+module_init(cg3_init);
+module_exit(cg3_exit);
+
+MODULE_DESCRIPTION("framebuffer driver for CGthree chipsets");
+MODULE_AUTHOR("David S. Miller <davem@davemloft.net>");
+MODULE_VERSION("2.0");
+MODULE_LICENSE("GPL");