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, 397 insertions, 0 deletions

diff --git a/drivers/video/fbdev/bw2.c b/drivers/video/fbdev/bw2.c
new file mode 100644
index 000000000..e757462af
--- /dev/null
+++ b/drivers/video/fbdev/bw2.c
@@ -0,0 +1,397 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* bw2.c: BWTWO 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 bw2_blank(int, struct fb_info *);
+
+static int bw2_sbusfb_mmap(struct fb_info *info, struct vm_area_struct *vma);
+static int bw2_sbusfb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg);
+
+/*
+ *  Frame buffer operations
+ */
+
+static const struct fb_ops bw2_ops = {
+	.owner			= THIS_MODULE,
+	FB_DEFAULT_SBUS_OPS(bw2),
+	.fb_blank		= bw2_blank,
+};
+
+/* OBio addresses for the bwtwo registers */
+#define BWTWO_REGISTER_OFFSET 0x400000
+
+struct bt_regs {
+	u32 addr;
+	u32 color_map;
+	u32 control;
+	u32 cursor;
+};
+
+struct bw2_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;
+};
+
+/* Status Register Constants */
+#define BWTWO_SR_RES_MASK	0x70
+#define BWTWO_SR_1600_1280	0x50
+#define BWTWO_SR_1152_900_76_A	0x40
+#define BWTWO_SR_1152_900_76_B	0x60
+#define BWTWO_SR_ID_MASK	0x0f
+#define BWTWO_SR_ID_MONO	0x02
+#define BWTWO_SR_ID_MONO_ECL	0x03
+#define BWTWO_SR_ID_MSYNC	0x04
+#define BWTWO_SR_ID_NOCONN	0x0a
+
+/* Control Register Constants */
+#define BWTWO_CTL_ENABLE_INTS   0x80
+#define BWTWO_CTL_ENABLE_VIDEO  0x40
+#define BWTWO_CTL_ENABLE_TIMING 0x20
+#define BWTWO_CTL_ENABLE_CURCMP 0x10
+#define BWTWO_CTL_XTAL_MASK     0x0C
+#define BWTWO_CTL_DIVISOR_MASK  0x03
+
+/* Status Register Constants */
+#define BWTWO_STAT_PENDING_INT  0x80
+#define BWTWO_STAT_MSENSE_MASK  0x70
+#define BWTWO_STAT_ID_MASK      0x0f
+
+struct bw2_par {
+	spinlock_t		lock;
+	struct bw2_regs		__iomem *regs;
+
+	u32			flags;
+#define BW2_FLAG_BLANKED	0x00000001
+
+	unsigned long		which_io;
+};
+
+/**
+ *      bw2_blank - Optional function.  Blanks the display.
+ *      @blank: the blank mode we want.
+ *      @info: frame buffer structure that represents a single frame buffer
+ */
+static int
+bw2_blank(int blank, struct fb_info *info)
+{
+	struct bw2_par *par = (struct bw2_par *) info->par;
+	struct bw2_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 |= BWTWO_CTL_ENABLE_VIDEO;
+		sbus_writeb(val, &regs->control);
+		par->flags &= ~BW2_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 &= ~BWTWO_CTL_ENABLE_VIDEO;
+		sbus_writeb(val, &regs->control);
+		par->flags |= BW2_FLAG_BLANKED;
+		break;
+	}
+
+	spin_unlock_irqrestore(&par->lock, flags);
+
+	return 0;
+}
+
+static const struct sbus_mmap_map bw2_mmap_map[] = {
+	{
+		.size = SBUS_MMAP_FBSIZE(1)
+	},
+	{ .size = 0 }
+};
+
+static int bw2_sbusfb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct bw2_par *par = (struct bw2_par *)info->par;
+
+	return sbusfb_mmap_helper(bw2_mmap_map,
+				  info->fix.smem_start, info->fix.smem_len,
+				  par->which_io,
+				  vma);
+}
+
+static int bw2_sbusfb_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg)
+{
+	return sbusfb_ioctl_helper(cmd, arg, info,
+				   FBTYPE_SUN2BW, 1, info->fix.smem_len);
+}
+
+/*
+ *  Initialisation
+ */
+
+static void bw2_init_fix(struct fb_info *info, int linebytes)
+{
+	strscpy(info->fix.id, "bwtwo", sizeof(info->fix.id));
+
+	info->fix.type = FB_TYPE_PACKED_PIXELS;
+	info->fix.visual = FB_VISUAL_MONO01;
+
+	info->fix.line_length = linebytes;
+
+	info->fix.accel = FB_ACCEL_SUN_BWTWO;
+}
+
+static u8 bw2regs_1600[] = {
+	0x14, 0x8b,	0x15, 0x28,	0x16, 0x03,	0x17, 0x13,
+	0x18, 0x7b,	0x19, 0x05,	0x1a, 0x34,	0x1b, 0x2e,
+	0x1c, 0x00,	0x1d, 0x0a,	0x1e, 0xff,	0x1f, 0x01,
+	0x10, 0x21,	0
+};
+
+static u8 bw2regs_ecl[] = {
+	0x14, 0x65,	0x15, 0x1e,	0x16, 0x04,	0x17, 0x0c,
+	0x18, 0x5e,	0x19, 0x03,	0x1a, 0xa7,	0x1b, 0x23,
+	0x1c, 0x00,	0x1d, 0x08,	0x1e, 0xff,	0x1f, 0x01,
+	0x10, 0x20,	0
+};
+
+static u8 bw2regs_analog[] = {
+	0x14, 0xbb,	0x15, 0x2b,	0x16, 0x03,	0x17, 0x13,
+	0x18, 0xb0,	0x19, 0x03,	0x1a, 0xa6,	0x1b, 0x22,
+	0x1c, 0x01,	0x1d, 0x05,	0x1e, 0xff,	0x1f, 0x01,
+	0x10, 0x20,	0
+};
+
+static u8 bw2regs_76hz[] = {
+	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 bw2regs_66hz[] = {
+	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 int bw2_do_default_mode(struct bw2_par *par, struct fb_info *info,
+			       int *linebytes)
+{
+	u8 status, mon;
+	u8 *p;
+
+	status = sbus_readb(&par->regs->status);
+	mon = status & BWTWO_SR_RES_MASK;
+	switch (status & BWTWO_SR_ID_MASK) {
+	case BWTWO_SR_ID_MONO_ECL:
+		if (mon == BWTWO_SR_1600_1280) {
+			p = bw2regs_1600;
+			info->var.xres = info->var.xres_virtual = 1600;
+			info->var.yres = info->var.yres_virtual = 1280;
+			*linebytes = 1600 / 8;
+		} else
+			p = bw2regs_ecl;
+		break;
+
+	case BWTWO_SR_ID_MONO:
+		p = bw2regs_analog;
+		break;
+
+	case BWTWO_SR_ID_MSYNC:
+		if (mon == BWTWO_SR_1152_900_76_A ||
+		    mon == BWTWO_SR_1152_900_76_B)
+			p = bw2regs_76hz;
+		else
+			p = bw2regs_66hz;
+		break;
+
+	case BWTWO_SR_ID_NOCONN:
+		return 0;
+
+	default:
+		printk(KERN_ERR "bw2: can't handle SR %02x\n",
+		       status);
+		return -EINVAL;
+	}
+	for ( ; *p; p += 2) {
+		u8 __iomem *regp = &((u8 __iomem *)par->regs)[p[0]];
+		sbus_writeb(p[1], regp);
+	}
+	return 0;
+}
+
+static int bw2_probe(struct platform_device *op)
+{
+	struct device_node *dp = op->dev.of_node;
+	struct fb_info *info;
+	struct bw2_par *par;
+	int linebytes, err;
+
+	info = framebuffer_alloc(sizeof(struct bw2_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, 1);
+	linebytes = of_getintprop_default(dp, "linebytes",
+					  info->var.xres);
+
+	info->var.red.length = info->var.green.length =
+		info->var.blue.length = info->var.bits_per_pixel;
+	info->var.red.offset = info->var.green.offset =
+		info->var.blue.offset = 0;
+
+	par->regs = of_ioremap(&op->resource[0], BWTWO_REGISTER_OFFSET,
+			       sizeof(struct bw2_regs), "bw2 regs");
+	if (!par->regs)
+		goto out_release_fb;
+
+	if (!of_property_present(dp, "width")) {
+		err = bw2_do_default_mode(par, info, &linebytes);
+		if (err)
+			goto out_unmap_regs;
+	}
+
+	info->fix.smem_len = PAGE_ALIGN(linebytes * info->var.yres);
+
+	info->fbops = &bw2_ops;
+
+	info->screen_base = of_ioremap(&op->resource[0], 0,
+				       info->fix.smem_len, "bw2 ram");
+	if (!info->screen_base) {
+		err = -ENOMEM;
+		goto out_unmap_regs;
+	}
+
+	bw2_blank(FB_BLANK_UNBLANK, info);
+
+	bw2_init_fix(info, linebytes);
+
+	err = register_framebuffer(info);
+	if (err < 0)
+		goto out_unmap_screen;
+
+	dev_set_drvdata(&op->dev, info);
+
+	printk(KERN_INFO "%pOF: bwtwo at %lx:%lx\n",
+	       dp, par->which_io, info->fix.smem_start);
+
+	return 0;
+
+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 bw2_regs));
+
+out_release_fb:
+	framebuffer_release(info);
+
+out_err:
+	return err;
+}
+
+static void bw2_remove(struct platform_device *op)
+{
+	struct fb_info *info = dev_get_drvdata(&op->dev);
+	struct bw2_par *par = info->par;
+
+	unregister_framebuffer(info);
+
+	of_iounmap(&op->resource[0], par->regs, sizeof(struct bw2_regs));
+	of_iounmap(&op->resource[0], info->screen_base, info->fix.smem_len);
+
+	framebuffer_release(info);
+}
+
+static const struct of_device_id bw2_match[] = {
+	{
+		.name = "bwtwo",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, bw2_match);
+
+static struct platform_driver bw2_driver = {
+	.driver = {
+		.name = "bw2",
+		.of_match_table = bw2_match,
+	},
+	.probe		= bw2_probe,
+	.remove		= bw2_remove,
+};
+
+static int __init bw2_init(void)
+{
+	if (fb_get_options("bw2fb", NULL))
+		return -ENODEV;
+
+	return platform_driver_register(&bw2_driver);
+}
+
+static void __exit bw2_exit(void)
+{
+	platform_driver_unregister(&bw2_driver);
+}
+
+module_init(bw2_init);
+module_exit(bw2_exit);
+
+MODULE_DESCRIPTION("framebuffer driver for BWTWO chipsets");
+MODULE_AUTHOR("David S. Miller <davem@davemloft.net>");
+MODULE_VERSION("2.0");
+MODULE_LICENSE("GPL");