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, 301 insertions, 0 deletions

diff --git a/drivers/video/fbdev/pmag-aa-fb.c b/drivers/video/fbdev/pmag-aa-fb.c
new file mode 100644
index 000000000..acfc8c70c
--- /dev/null
+++ b/drivers/video/fbdev/pmag-aa-fb.c
@@ -0,0 +1,301 @@
+/*
+ *	linux/drivers/video/pmag-aa-fb.c
+ *	Copyright 2002 Karsten Merker <merker@debian.org>
+ *
+ *	PMAG-AA TurboChannel framebuffer card support ... derived from
+ *	pmag-ba-fb.c, which is Copyright (C) 1999, 2000, 2001 by
+ *	Michael Engel <engel@unix-ag.org>, Karsten Merker <merker@debian.org>
+ *	and Harald Koerfgen <hkoerfg@web.de>, which itself is derived from
+ *	"HP300 Topcat framebuffer support (derived from macfb of all things)
+ *	Phil Blundell <philb@gnu.org> 1998"
+ *	Copyright (c) 2016  Maciej W. Rozycki
+ *
+ *	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.
+ *
+ *	2002-09-28  Karsten Merker <merker@linuxtag.org>
+ *		Version 0.01: First try to get a PMAG-AA running.
+ *
+ *	2003-02-24  Thiemo Seufer  <seufer@csv.ica.uni-stuttgart.de>
+ *		Version 0.02: Major code cleanup.
+ *
+ *	2003-09-21  Thiemo Seufer  <seufer@csv.ica.uni-stuttgart.de>
+ *		Hardware cursor support.
+ *
+ *	2016-02-21  Maciej W. Rozycki  <macro@linux-mips.org>
+ *		Version 0.03: Rewritten for the new FB and TC APIs.
+ */
+
+#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/tc.h>
+#include <linux/timer.h>
+
+#include "bt455.h"
+#include "bt431.h"
+
+/* Version information */
+#define DRIVER_VERSION "0.03"
+#define DRIVER_AUTHOR "Karsten Merker <merker@linuxtag.org>"
+#define DRIVER_DESCRIPTION "PMAG-AA Framebuffer Driver"
+
+/*
+ * Bt455 RAM DAC register base offset (rel. to TC slot base address).
+ */
+#define PMAG_AA_BT455_OFFSET		0x100000
+
+/*
+ * Bt431 cursor generator offset (rel. to TC slot base address).
+ */
+#define PMAG_AA_BT431_OFFSET		0x180000
+
+/*
+ * Begin of PMAG-AA framebuffer memory relative to TC slot address,
+ * resolution is 1280x1024x1 (8 bits deep, but only LSB is used).
+ */
+#define PMAG_AA_ONBOARD_FBMEM_OFFSET	0x200000
+
+struct aafb_par {
+	void __iomem *mmio;
+	struct bt455_regs __iomem *bt455;
+	struct bt431_regs __iomem *bt431;
+};
+
+static const struct fb_var_screeninfo aafb_defined = {
+	.xres		= 1280,
+	.yres		= 1024,
+	.xres_virtual	= 2048,
+	.yres_virtual	= 1024,
+	.bits_per_pixel	= 8,
+	.grayscale	= 1,
+	.red.length	= 0,
+	.green.length	= 1,
+	.blue.length	= 0,
+	.activate	= FB_ACTIVATE_NOW,
+	.accel_flags	= FB_ACCEL_NONE,
+	.pixclock	= 7645,
+	.left_margin	= 224,
+	.right_margin	= 32,
+	.upper_margin	= 33,
+	.lower_margin	= 3,
+	.hsync_len	= 160,
+	.vsync_len	= 3,
+	.sync		= FB_SYNC_ON_GREEN,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+static const struct fb_fix_screeninfo aafb_fix = {
+	.id		= "PMAG-AA",
+	.smem_len	= (2048 * 1024),
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.visual		= FB_VISUAL_MONO10,
+	.ypanstep	= 1,
+	.ywrapstep	= 1,
+	.line_length	= 2048,
+	.mmio_len	= PMAG_AA_ONBOARD_FBMEM_OFFSET - PMAG_AA_BT455_OFFSET,
+};
+
+static int aafb_cursor(struct fb_info *info, struct fb_cursor *cursor)
+{
+	struct aafb_par *par = info->par;
+
+	if (cursor->image.height > BT431_CURSOR_SIZE ||
+	    cursor->image.width > BT431_CURSOR_SIZE) {
+		bt431_erase_cursor(par->bt431);
+		return -EINVAL;
+	}
+
+	if (!cursor->enable)
+		bt431_erase_cursor(par->bt431);
+
+	if (cursor->set & FB_CUR_SETPOS)
+		bt431_position_cursor(par->bt431,
+				      cursor->image.dx, cursor->image.dy);
+	if (cursor->set & FB_CUR_SETCMAP) {
+		u8 fg = cursor->image.fg_color ? 0xf : 0x0;
+		u8 bg = cursor->image.bg_color ? 0xf : 0x0;
+
+		bt455_write_cmap_entry(par->bt455, 8, bg);
+		bt455_write_cmap_next(par->bt455, bg);
+		bt455_write_ovly_next(par->bt455, fg);
+	}
+	if (cursor->set & (FB_CUR_SETSIZE | FB_CUR_SETSHAPE | FB_CUR_SETIMAGE))
+		bt431_set_cursor(par->bt431,
+				 cursor->image.data, cursor->mask, cursor->rop,
+				 cursor->image.width, cursor->image.height);
+
+	if (cursor->enable)
+		bt431_enable_cursor(par->bt431);
+
+	return 0;
+}
+
+/* 0 unblanks, any other blanks. */
+
+static int aafb_blank(int blank, struct fb_info *info)
+{
+	struct aafb_par *par = info->par;
+	u8 val = blank ? 0x00 : 0x0f;
+
+	bt455_write_cmap_entry(par->bt455, 1, val);
+	return 0;
+}
+
+static const struct fb_ops aafb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_blank	= aafb_blank,
+	.fb_cursor	= aafb_cursor,
+};
+
+static int pmagaafb_probe(struct device *dev)
+{
+	struct tc_dev *tdev = to_tc_dev(dev);
+	resource_size_t start, len;
+	struct fb_info *info;
+	struct aafb_par *par;
+	int err;
+
+	info = framebuffer_alloc(sizeof(struct aafb_par), dev);
+	if (!info)
+		return -ENOMEM;
+
+	par = info->par;
+	dev_set_drvdata(dev, info);
+
+	info->fbops = &aafb_ops;
+	info->fix = aafb_fix;
+	info->var = aafb_defined;
+
+	/* Request the I/O MEM resource. */
+	start = tdev->resource.start;
+	len = tdev->resource.end - start + 1;
+	if (!request_mem_region(start, len, dev_name(dev))) {
+		printk(KERN_ERR "%s: Cannot reserve FB region\n",
+		       dev_name(dev));
+		err = -EBUSY;
+		goto err_alloc;
+	}
+
+	/* MMIO mapping setup. */
+	info->fix.mmio_start = start + PMAG_AA_BT455_OFFSET;
+	par->mmio = ioremap(info->fix.mmio_start, info->fix.mmio_len);
+	if (!par->mmio) {
+		printk(KERN_ERR "%s: Cannot map MMIO\n", dev_name(dev));
+		err = -ENOMEM;
+		goto err_resource;
+	}
+	par->bt455 = par->mmio - PMAG_AA_BT455_OFFSET + PMAG_AA_BT455_OFFSET;
+	par->bt431 = par->mmio - PMAG_AA_BT455_OFFSET + PMAG_AA_BT431_OFFSET;
+
+	/* Frame buffer mapping setup. */
+	info->fix.smem_start = start + PMAG_AA_ONBOARD_FBMEM_OFFSET;
+	info->screen_base = ioremap(info->fix.smem_start,
+					    info->fix.smem_len);
+	if (!info->screen_base) {
+		printk(KERN_ERR "%s: Cannot map FB\n", dev_name(dev));
+		err = -ENOMEM;
+		goto err_mmio_map;
+	}
+	info->screen_size = info->fix.smem_len;
+
+	/* Init colormap. */
+	bt455_write_cmap_entry(par->bt455, 0, 0x0);
+	bt455_write_cmap_next(par->bt455, 0xf);
+
+	/* Init hardware cursor. */
+	bt431_erase_cursor(par->bt431);
+	bt431_init_cursor(par->bt431);
+
+	err = register_framebuffer(info);
+	if (err < 0) {
+		printk(KERN_ERR "%s: Cannot register framebuffer\n",
+		       dev_name(dev));
+		goto err_smem_map;
+	}
+
+	get_device(dev);
+
+	pr_info("fb%d: %s frame buffer device at %s\n",
+		info->node, info->fix.id, dev_name(dev));
+
+	return 0;
+
+
+err_smem_map:
+	iounmap(info->screen_base);
+
+err_mmio_map:
+	iounmap(par->mmio);
+
+err_resource:
+	release_mem_region(start, len);
+
+err_alloc:
+	framebuffer_release(info);
+	return err;
+}
+
+static int pmagaafb_remove(struct device *dev)
+{
+	struct tc_dev *tdev = to_tc_dev(dev);
+	struct fb_info *info = dev_get_drvdata(dev);
+	struct aafb_par *par = info->par;
+	resource_size_t start, len;
+
+	put_device(dev);
+	unregister_framebuffer(info);
+	iounmap(info->screen_base);
+	iounmap(par->mmio);
+	start = tdev->resource.start;
+	len = tdev->resource.end - start + 1;
+	release_mem_region(start, len);
+	framebuffer_release(info);
+	return 0;
+}
+
+/*
+ * Initialise the framebuffer.
+ */
+static const struct tc_device_id pmagaafb_tc_table[] = {
+	{ "DEC     ", "PMAG-AA " },
+	{ }
+};
+MODULE_DEVICE_TABLE(tc, pmagaafb_tc_table);
+
+static struct tc_driver pmagaafb_driver = {
+	.id_table	= pmagaafb_tc_table,
+	.driver		= {
+		.name	= "pmagaafb",
+		.bus	= &tc_bus_type,
+		.probe	= pmagaafb_probe,
+		.remove	= pmagaafb_remove,
+	},
+};
+
+static int __init pmagaafb_init(void)
+{
+#ifndef MODULE
+	if (fb_get_options("pmagaafb", NULL))
+		return -ENXIO;
+#endif
+	return tc_register_driver(&pmagaafb_driver);
+}
+
+static void __exit pmagaafb_exit(void)
+{
+	tc_unregister_driver(&pmagaafb_driver);
+}
+
+module_init(pmagaafb_init);
+module_exit(pmagaafb_exit);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESCRIPTION);
+MODULE_LICENSE("GPL");