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, 395 insertions, 0 deletions

diff --git a/drivers/video/console/sticon.c b/drivers/video/console/sticon.c
new file mode 100644
index 000000000..6f58e6a9e
--- /dev/null
+++ b/drivers/video/console/sticon.c
@@ -0,0 +1,395 @@
+/*
+ *  linux/drivers/video/console/sticon.c - console driver using HP's STI firmware
+ *
+ *	Copyright (C) 2000 Philipp Rumpf <prumpf@tux.org>
+ *	Copyright (C) 2002-2020 Helge Deller <deller@gmx.de>
+ *
+ *  Based on linux/drivers/video/vgacon.c and linux/drivers/video/fbcon.c,
+ *  which were
+ *
+ *	Created 28 Sep 1997 by Geert Uytterhoeven
+ *	Rewritten by Martin Mares <mj@ucw.cz>, July 1998
+ *	Copyright (C) 1991, 1992  Linus Torvalds
+ *			    1995  Jay Estabrook
+ *	Copyright (C) 1995 Geert Uytterhoeven
+ *	Copyright (C) 1993 Bjoern Brauel
+ *			   Roman Hodek
+ *	Copyright (C) 1993 Hamish Macdonald
+ *			   Greg Harp
+ *	Copyright (C) 1994 David Carter [carter@compsci.bristol.ac.uk]
+ *
+ *	      with work by William Rucklidge (wjr@cs.cornell.edu)
+ *			   Geert Uytterhoeven
+ *			   Jes Sorensen (jds@kom.auc.dk)
+ *			   Martin Apel
+ *	      with work by Guenther Kelleter
+ *			   Martin Schaller
+ *			   Andreas Schwab
+ *			   Emmanuel Marty (core@ggi-project.org)
+ *			   Jakub Jelinek (jj@ultra.linux.cz)
+ *			   Martin Mares <mj@ucw.cz>
+ *
+ *  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.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/errno.h>
+#include <linux/vt_kern.h>
+#include <linux/kd.h>
+#include <linux/selection.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/font.h>
+#include <linux/crc32.h>
+#include <linux/fb.h>
+
+#include <asm/io.h>
+
+#include <video/sticore.h>
+
+/* switching to graphics mode */
+#define BLANK 0
+static int vga_is_gfx;
+
+#define STI_DEF_FONT	sticon_sti->font
+
+/* borrowed from fbcon.c */
+#define FNTREFCOUNT(fd)	(fd->refcount)
+#define FNTCRC(fd)	(fd->crc)
+static struct sti_cooked_font *font_data[MAX_NR_CONSOLES];
+
+/* this is the sti_struct used for this console */
+static struct sti_struct *sticon_sti;
+
+static const char *sticon_startup(void)
+{
+    return "STI console";
+}
+
+static void sticon_putcs(struct vc_data *conp, const u16 *s, unsigned int count,
+			 unsigned int ypos, unsigned int xpos)
+{
+    if (vga_is_gfx || console_blanked)
+	    return;
+
+    if (conp->vc_mode != KD_TEXT)
+    	    return;
+
+    while (count--) {
+	sti_putc(sticon_sti, scr_readw(s++), ypos, xpos++,
+		 font_data[conp->vc_num]);
+    }
+}
+
+static void sticon_cursor(struct vc_data *conp, bool enable)
+{
+    unsigned short car1;
+
+    /* no cursor update if screen is blanked */
+    if (vga_is_gfx || console_blanked)
+	return;
+
+    car1 = conp->vc_screenbuf[conp->state.x + conp->state.y * conp->vc_cols];
+    if (!enable) {
+	sti_putc(sticon_sti, car1, conp->state.y, conp->state.x,
+		 font_data[conp->vc_num]);
+	return;
+    }
+
+    switch (CUR_SIZE(conp->vc_cursor_type)) {
+    case CUR_UNDERLINE:
+    case CUR_LOWER_THIRD:
+    case CUR_LOWER_HALF:
+    case CUR_TWO_THIRDS:
+    case CUR_BLOCK:
+	sti_putc(sticon_sti, (car1 & 255) + (0 << 8) + (7 << 11),
+		 conp->state.y, conp->state.x, font_data[conp->vc_num]);
+	break;
+    }
+}
+
+static bool sticon_scroll(struct vc_data *conp, unsigned int t,
+		unsigned int b, enum con_scroll dir, unsigned int count)
+{
+    struct sti_struct *sti = sticon_sti;
+
+    if (vga_is_gfx)
+        return false;
+
+    sticon_cursor(conp, false);
+
+    switch (dir) {
+    case SM_UP:
+	sti_bmove(sti, t + count, 0, t, 0, b - t - count, conp->vc_cols,
+		  font_data[conp->vc_num]);
+	sti_clear(sti, b - count, 0, count, conp->vc_cols,
+		  conp->vc_video_erase_char, font_data[conp->vc_num]);
+	break;
+
+    case SM_DOWN:
+	sti_bmove(sti, t, 0, t + count, 0, b - t - count, conp->vc_cols,
+		  font_data[conp->vc_num]);
+	sti_clear(sti, t, 0, count, conp->vc_cols,
+		  conp->vc_video_erase_char, font_data[conp->vc_num]);
+	break;
+    }
+
+    return false;
+}
+
+static void sticon_set_def_font(int unit)
+{
+	if (font_data[unit] != STI_DEF_FONT) {
+		if (--FNTREFCOUNT(font_data[unit]) == 0) {
+			kfree(font_data[unit]->raw_ptr);
+			kfree(font_data[unit]);
+		}
+		font_data[unit] = STI_DEF_FONT;
+	}
+}
+
+static int sticon_set_font(struct vc_data *vc, const struct console_font *op,
+			   unsigned int vpitch)
+{
+	struct sti_struct *sti = sticon_sti;
+	int vc_cols, vc_rows, vc_old_cols, vc_old_rows;
+	int unit = vc->vc_num;
+	int w = op->width;
+	int h = op->height;
+	int size, i, bpc, pitch;
+	struct sti_rom_font *new_font;
+	struct sti_cooked_font *cooked_font;
+	unsigned char *data = op->data, *p;
+
+	if ((w < 6) || (h < 6) || (w > 32) || (h > 32) || (vpitch != 32)
+	    || (op->charcount != 256 && op->charcount != 512))
+		return -EINVAL;
+	pitch = ALIGN(w, 8) / 8;
+	bpc = pitch * h;
+	size = bpc * op->charcount;
+
+	new_font = kmalloc(sizeof(*new_font) + size, STI_LOWMEM);
+	if (!new_font)
+		return -ENOMEM;
+
+	new_font->first_char = 0;
+	new_font->last_char = op->charcount - 1;
+	new_font->width = w;
+	new_font->height = h;
+	new_font->font_type = STI_FONT_HPROMAN8;
+	new_font->bytes_per_char = bpc;
+	new_font->underline_height = 0;
+	new_font->underline_pos = 0;
+
+	cooked_font = kzalloc_obj(*cooked_font);
+	if (!cooked_font) {
+		kfree(new_font);
+		return -ENOMEM;
+	}
+	cooked_font->raw = new_font;
+	cooked_font->raw_ptr = new_font;
+	cooked_font->width = w;
+	cooked_font->height = h;
+	FNTREFCOUNT(cooked_font) = 0;	/* usage counter */
+
+	p = (unsigned char *) new_font;
+	p += sizeof(*new_font);
+	for (i = 0; i < op->charcount; i++) {
+		memcpy(p, data, bpc);
+		data += pitch*32;
+		p += bpc;
+	}
+	FNTCRC(cooked_font) = crc32(0, new_font, size + sizeof(*new_font));
+	sti_font_convert_bytemode(sti, cooked_font);
+	new_font = cooked_font->raw_ptr;
+
+	/* check if font is already used by other console */
+	for (i = 0; i < MAX_NR_CONSOLES; i++) {
+		if (font_data[i] != STI_DEF_FONT
+		    && (FNTCRC(font_data[i]) == FNTCRC(cooked_font))) {
+			kfree(new_font);
+			kfree(cooked_font);
+			/* current font is the same as the new one */
+			if (i == unit)
+				return 0;
+			cooked_font = font_data[i];
+			new_font = cooked_font->raw_ptr;
+			break;
+		}
+	}
+
+	/* clear screen with old font: we now may have less rows */
+	vc_old_rows = vc->vc_rows;
+	vc_old_cols = vc->vc_cols;
+	sti_clear(sticon_sti, 0, 0, vc_old_rows, vc_old_cols,
+		  vc->vc_video_erase_char, font_data[vc->vc_num]);
+
+	/* delete old font in case it is a user font */
+	sticon_set_def_font(unit);
+
+	FNTREFCOUNT(cooked_font)++;
+	font_data[unit] = cooked_font;
+
+	vc_cols = sti_onscreen_x(sti) / cooked_font->width;
+	vc_rows = sti_onscreen_y(sti) / cooked_font->height;
+	vc_resize(vc, vc_cols, vc_rows);
+
+	/* need to repaint screen if cols & rows are same as old font */
+	if (vc_cols == vc_old_cols && vc_rows == vc_old_rows)
+		update_screen(vc);
+
+	return 0;
+}
+
+static int sticon_font_default(struct vc_data *vc, struct console_font *op,
+			       const char *name)
+{
+	sticon_set_def_font(vc->vc_num);
+
+	return 0;
+}
+
+static int sticon_font_set(struct vc_data *vc, const struct console_font *font,
+			   unsigned int vpitch, unsigned int flags)
+{
+	return sticon_set_font(vc, font, vpitch);
+}
+
+static void sticon_init(struct vc_data *c, bool init)
+{
+    struct sti_struct *sti = sticon_sti;
+    int vc_cols, vc_rows;
+
+    sti_set(sti, 0, 0, sti_onscreen_y(sti), sti_onscreen_x(sti), 0);
+    vc_cols = sti_onscreen_x(sti) / sti->font->width;
+    vc_rows = sti_onscreen_y(sti) / sti->font->height;
+    c->vc_can_do_color = 1;
+
+    if (init) {
+	c->vc_cols = vc_cols;
+	c->vc_rows = vc_rows;
+    } else {
+	vc_resize(c, vc_cols, vc_rows);
+    }
+}
+
+static void sticon_deinit(struct vc_data *c)
+{
+    int i;
+
+    /* free memory used by user font */
+    for (i = 0; i < MAX_NR_CONSOLES; i++)
+	sticon_set_def_font(i);
+}
+
+static void sticon_clear(struct vc_data *conp, unsigned int sy, unsigned int sx,
+			 unsigned int width)
+{
+    sti_clear(sticon_sti, sy, sx, 1, width,
+	      conp->vc_video_erase_char, font_data[conp->vc_num]);
+}
+
+static bool sticon_switch(struct vc_data *conp)
+{
+    return true;	/* needs refreshing */
+}
+
+static bool sticon_blank(struct vc_data *c, enum vesa_blank_mode blank,
+			 bool mode_switch)
+{
+    if (blank == VESA_NO_BLANKING) {
+	if (mode_switch)
+	    vga_is_gfx = 0;
+	return true;
+    }
+    sti_clear(sticon_sti, 0, 0, c->vc_rows, c->vc_cols, BLANK,
+	      font_data[c->vc_num]);
+    if (mode_switch)
+	vga_is_gfx = 1;
+
+    return true;
+}
+
+static u8 sticon_build_attr(struct vc_data *conp, u8 color,
+			    enum vc_intensity intens,
+			    bool blink, bool underline, bool reverse,
+			    bool italic)
+{
+	u8 fg = color & 7;
+	u8 bg = (color & 0x70) >> 4;
+
+	if (reverse)
+		return (fg << 3) | bg;
+	else
+		return (bg << 3) | fg;
+}
+
+static void sticon_invert_region(struct vc_data *conp, u16 *p, int count)
+{
+    int col = 1; /* vga_can_do_color; */
+
+    while (count--) {
+	u16 a = scr_readw(p);
+
+	if (col)
+		a = ((a) & 0x88ff) | (((a) & 0x7000) >> 4) | (((a) & 0x0700) << 4);
+	else
+		a = ((a & 0x0700) == 0x0100) ? 0x7000 : 0x7700;
+
+	scr_writew(a, p++);
+    }
+}
+
+static const struct consw sti_con = {
+	.owner			= THIS_MODULE,
+	.con_startup		= sticon_startup,
+	.con_init		= sticon_init,
+	.con_deinit		= sticon_deinit,
+	.con_clear		= sticon_clear,
+	.con_putcs		= sticon_putcs,
+	.con_cursor		= sticon_cursor,
+	.con_scroll		= sticon_scroll,
+	.con_switch		= sticon_switch,
+	.con_blank		= sticon_blank,
+	.con_font_set		= sticon_font_set,
+	.con_font_default	= sticon_font_default,
+	.con_build_attr		= sticon_build_attr,
+	.con_invert_region	= sticon_invert_region,
+};
+
+
+
+static int __init sticonsole_init(void)
+{
+    int err, i;
+
+    /* already initialized ? */
+    if (sticon_sti)
+	 return 0;
+
+    sticon_sti = sti_get_rom(0);
+    if (!sticon_sti)
+	return -ENODEV;
+
+    for (i = 0; i < MAX_NR_CONSOLES; i++)
+	font_data[i] = STI_DEF_FONT;
+
+    pr_info("sticon: Initializing STI text console on %s at [%s]\n",
+	sticon_sti->sti_data->inq_outptr.dev_name,
+	sticon_sti->pa_path);
+    console_lock();
+    err = do_take_over_console(&sti_con, 0, MAX_NR_CONSOLES - 1,
+		PAGE0->mem_cons.cl_class != CL_DUPLEX);
+    console_unlock();
+
+    return err;
+}
+
+module_init(sticonsole_init);
+MODULE_DESCRIPTION("HP STI console driver");
+MODULE_LICENSE("GPL");