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, 408 insertions, 0 deletions

diff --git a/drivers/video/fbdev/pmagb-b-fb.c b/drivers/video/fbdev/pmagb-b-fb.c
new file mode 100644
index 000000000..643249246
--- /dev/null
+++ b/drivers/video/fbdev/pmagb-b-fb.c
@@ -0,0 +1,408 @@
+/*
+ *	linux/drivers/video/pmagb-b-fb.c
+ *
+ *	PMAGB-B TURBOchannel Smart Frame Buffer (SFB) card support,
+ *	derived from:
+ *	"HP300 Topcat framebuffer support (derived from macfb of all things)
+ *	Phil Blundell <philb@gnu.org> 1998", the original code can be
+ *	found in the file hpfb.c in the same directory.
+ *
+ *	DECstation related code Copyright (C) 1999, 2000, 2001 by
+ *	Michael Engel <engel@unix-ag.org>,
+ *	Karsten Merker <merker@linuxtag.org> and
+ *	Harald Koerfgen.
+ *	Copyright (c) 2005, 2006  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.
+ */
+
+#include <linux/compiler.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/tc.h>
+#include <linux/types.h>
+
+#include <asm/io.h>
+
+#include <video/pmagb-b-fb.h>
+
+
+struct pmagbbfb_par {
+	volatile void __iomem *mmio;
+	volatile void __iomem *smem;
+	volatile u32 __iomem *sfb;
+	volatile u32 __iomem *dac;
+	unsigned int osc0;
+	unsigned int osc1;
+	int slot;
+};
+
+
+static const struct fb_var_screeninfo pmagbbfb_defined = {
+	.bits_per_pixel	= 8,
+	.red.length	= 8,
+	.green.length	= 8,
+	.blue.length	= 8,
+	.activate	= FB_ACTIVATE_NOW,
+	.height		= -1,
+	.width		= -1,
+	.accel_flags	= FB_ACCEL_NONE,
+	.sync		= FB_SYNC_ON_GREEN,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+static const struct fb_fix_screeninfo pmagbbfb_fix = {
+	.id		= "PMAGB-BA",
+	.smem_len	= (2048 * 1024),
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.visual		= FB_VISUAL_PSEUDOCOLOR,
+	.mmio_len	= PMAGB_B_FBMEM,
+};
+
+
+static inline void sfb_write(struct pmagbbfb_par *par, unsigned int reg, u32 v)
+{
+	writel(v, par->sfb + reg / 4);
+}
+
+static inline u32 sfb_read(struct pmagbbfb_par *par, unsigned int reg)
+{
+	return readl(par->sfb + reg / 4);
+}
+
+static inline void dac_write(struct pmagbbfb_par *par, unsigned int reg, u8 v)
+{
+	writeb(v, par->dac + reg / 4);
+}
+
+static inline u8 dac_read(struct pmagbbfb_par *par, unsigned int reg)
+{
+	return readb(par->dac + reg / 4);
+}
+
+static inline void gp0_write(struct pmagbbfb_par *par, u32 v)
+{
+	writel(v, par->mmio + PMAGB_B_GP0);
+}
+
+
+/*
+ * Set the palette.
+ */
+static int pmagbbfb_setcolreg(unsigned int regno, unsigned int red,
+			      unsigned int green, unsigned int blue,
+			      unsigned int transp, struct fb_info *info)
+{
+	struct pmagbbfb_par *par = info->par;
+
+	if (regno >= info->cmap.len)
+		return 1;
+
+	red   >>= 8;	/* The cmap fields are 16 bits    */
+	green >>= 8;	/* wide, but the hardware colormap */
+	blue  >>= 8;	/* registers are only 8 bits wide */
+
+	mb();
+	dac_write(par, BT459_ADDR_LO, regno);
+	dac_write(par, BT459_ADDR_HI, 0x00);
+	wmb();
+	dac_write(par, BT459_CMAP, red);
+	wmb();
+	dac_write(par, BT459_CMAP, green);
+	wmb();
+	dac_write(par, BT459_CMAP, blue);
+
+	return 0;
+}
+
+static const struct fb_ops pmagbbfb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg	= pmagbbfb_setcolreg,
+};
+
+
+/*
+ * Turn the hardware cursor off.
+ */
+static void pmagbbfb_erase_cursor(struct fb_info *info)
+{
+	struct pmagbbfb_par *par = info->par;
+
+	mb();
+	dac_write(par, BT459_ADDR_LO, 0x00);
+	dac_write(par, BT459_ADDR_HI, 0x03);
+	wmb();
+	dac_write(par, BT459_DATA, 0x00);
+}
+
+/*
+ * Set up screen parameters.
+ */
+static void pmagbbfb_screen_setup(struct fb_info *info)
+{
+	struct pmagbbfb_par *par = info->par;
+
+	info->var.xres = ((sfb_read(par, SFB_REG_VID_HOR) >>
+			   SFB_VID_HOR_PIX_SHIFT) & SFB_VID_HOR_PIX_MASK) * 4;
+	info->var.xres_virtual = info->var.xres;
+	info->var.yres = (sfb_read(par, SFB_REG_VID_VER) >>
+			  SFB_VID_VER_SL_SHIFT) & SFB_VID_VER_SL_MASK;
+	info->var.yres_virtual = info->var.yres;
+	info->var.left_margin = ((sfb_read(par, SFB_REG_VID_HOR) >>
+				  SFB_VID_HOR_BP_SHIFT) &
+				 SFB_VID_HOR_BP_MASK) * 4;
+	info->var.right_margin = ((sfb_read(par, SFB_REG_VID_HOR) >>
+				   SFB_VID_HOR_FP_SHIFT) &
+				  SFB_VID_HOR_FP_MASK) * 4;
+	info->var.upper_margin = (sfb_read(par, SFB_REG_VID_VER) >>
+				  SFB_VID_VER_BP_SHIFT) & SFB_VID_VER_BP_MASK;
+	info->var.lower_margin = (sfb_read(par, SFB_REG_VID_VER) >>
+				  SFB_VID_VER_FP_SHIFT) & SFB_VID_VER_FP_MASK;
+	info->var.hsync_len = ((sfb_read(par, SFB_REG_VID_HOR) >>
+				SFB_VID_HOR_SYN_SHIFT) &
+			       SFB_VID_HOR_SYN_MASK) * 4;
+	info->var.vsync_len = (sfb_read(par, SFB_REG_VID_VER) >>
+			       SFB_VID_VER_SYN_SHIFT) & SFB_VID_VER_SYN_MASK;
+
+	info->fix.line_length = info->var.xres;
+};
+
+/*
+ * Determine oscillator configuration.
+ */
+static void pmagbbfb_osc_setup(struct fb_info *info)
+{
+	static unsigned int pmagbbfb_freqs[] = {
+		130808, 119843, 104000, 92980, 74370, 72800,
+		69197, 66000, 65000, 50350, 36000, 32000, 25175
+	};
+	struct pmagbbfb_par *par = info->par;
+	struct tc_bus *tbus = to_tc_dev(info->device)->bus;
+	u32 count0 = 8, count1 = 8, counttc = 16 * 256 + 8;
+	u32 freq0, freq1, freqtc = tc_get_speed(tbus) / 250;
+	int i, j;
+
+	gp0_write(par, 0);				/* select Osc0 */
+	for (j = 0; j < 16; j++) {
+		mb();
+		sfb_write(par, SFB_REG_TCCLK_COUNT, 0);
+		mb();
+		for (i = 0; i < 100; i++) {	/* nominally max. 20.5us */
+			if (sfb_read(par, SFB_REG_TCCLK_COUNT) == 0)
+				break;
+			udelay(1);
+		}
+		count0 += sfb_read(par, SFB_REG_VIDCLK_COUNT);
+	}
+
+	gp0_write(par, 1);				/* select Osc1 */
+	for (j = 0; j < 16; j++) {
+		mb();
+		sfb_write(par, SFB_REG_TCCLK_COUNT, 0);
+
+		for (i = 0; i < 100; i++) {	/* nominally max. 20.5us */
+			if (sfb_read(par, SFB_REG_TCCLK_COUNT) == 0)
+				break;
+			udelay(1);
+		}
+		count1 += sfb_read(par, SFB_REG_VIDCLK_COUNT);
+	}
+
+	freq0 = (freqtc * count0 + counttc / 2) / counttc;
+	par->osc0 = freq0;
+	if (freq0 >= pmagbbfb_freqs[0] - (pmagbbfb_freqs[0] + 32) / 64 &&
+	    freq0 <= pmagbbfb_freqs[0] + (pmagbbfb_freqs[0] + 32) / 64)
+		par->osc0 = pmagbbfb_freqs[0];
+
+	freq1 = (par->osc0 * count1 + count0 / 2) / count0;
+	par->osc1 = freq1;
+	for (i = 0; i < ARRAY_SIZE(pmagbbfb_freqs); i++)
+		if (freq1 >= pmagbbfb_freqs[i] -
+			     (pmagbbfb_freqs[i] + 128) / 256 &&
+		    freq1 <= pmagbbfb_freqs[i] +
+			     (pmagbbfb_freqs[i] + 128) / 256) {
+			par->osc1 = pmagbbfb_freqs[i];
+			break;
+		}
+
+	if (par->osc0 - par->osc1 <= (par->osc0 + par->osc1 + 256) / 512 ||
+	    par->osc1 - par->osc0 <= (par->osc0 + par->osc1 + 256) / 512)
+		par->osc1 = 0;
+
+	gp0_write(par, par->osc1 != 0);			/* reselect OscX */
+
+	info->var.pixclock = par->osc1 ?
+			     (1000000000 + par->osc1 / 2) / par->osc1 :
+			     (1000000000 + par->osc0 / 2) / par->osc0;
+};
+
+
+static int pmagbbfb_probe(struct device *dev)
+{
+	struct tc_dev *tdev = to_tc_dev(dev);
+	resource_size_t start, len;
+	struct fb_info *info;
+	struct pmagbbfb_par *par;
+	char freq0[12], freq1[12];
+	u32 vid_base;
+	int err;
+
+	info = framebuffer_alloc(sizeof(struct pmagbbfb_par), dev);
+	if (!info)
+		return -ENOMEM;
+
+	par = info->par;
+	dev_set_drvdata(dev, info);
+
+	if (fb_alloc_cmap(&info->cmap, 256, 0) < 0) {
+		printk(KERN_ERR "%s: Cannot allocate color map\n",
+		       dev_name(dev));
+		err = -ENOMEM;
+		goto err_alloc;
+	}
+
+	info->fbops = &pmagbbfb_ops;
+	info->fix = pmagbbfb_fix;
+	info->var = pmagbbfb_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_cmap;
+	}
+
+	/* MMIO mapping setup.  */
+	info->fix.mmio_start = start;
+	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->sfb = par->mmio + PMAGB_B_SFB;
+	par->dac = par->mmio + PMAGB_B_BT459;
+
+	/* Frame buffer mapping setup.  */
+	info->fix.smem_start = start + PMAGB_B_FBMEM;
+	par->smem = ioremap(info->fix.smem_start, info->fix.smem_len);
+	if (!par->smem) {
+		printk(KERN_ERR "%s: Cannot map FB\n", dev_name(dev));
+		err = -ENOMEM;
+		goto err_mmio_map;
+	}
+	vid_base = sfb_read(par, SFB_REG_VID_BASE);
+	info->screen_base = (void __iomem *)par->smem + vid_base * 0x1000;
+	info->screen_size = info->fix.smem_len - 2 * vid_base * 0x1000;
+
+	pmagbbfb_erase_cursor(info);
+	pmagbbfb_screen_setup(info);
+	pmagbbfb_osc_setup(info);
+
+	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);
+
+	snprintf(freq0, sizeof(freq0), "%u.%03uMHz",
+		 par->osc0 / 1000, par->osc0 % 1000);
+	snprintf(freq1, sizeof(freq1), "%u.%03uMHz",
+		 par->osc1 / 1000, par->osc1 % 1000);
+
+	fb_info(info, "%s frame buffer device at %s\n",
+		info->fix.id, dev_name(dev));
+	fb_info(info, "Osc0: %s, Osc1: %s, Osc%u selected\n",
+		freq0, par->osc1 ? freq1 : "disabled", par->osc1 != 0);
+
+	return 0;
+
+
+err_smem_map:
+	iounmap(par->smem);
+
+err_mmio_map:
+	iounmap(par->mmio);
+
+err_resource:
+	release_mem_region(start, len);
+
+err_cmap:
+	fb_dealloc_cmap(&info->cmap);
+
+err_alloc:
+	framebuffer_release(info);
+	return err;
+}
+
+static int pmagbbfb_remove(struct device *dev)
+{
+	struct tc_dev *tdev = to_tc_dev(dev);
+	struct fb_info *info = dev_get_drvdata(dev);
+	struct pmagbbfb_par *par = info->par;
+	resource_size_t start, len;
+
+	put_device(dev);
+	unregister_framebuffer(info);
+	iounmap(par->smem);
+	iounmap(par->mmio);
+	start = tdev->resource.start;
+	len = tdev->resource.end - start + 1;
+	release_mem_region(start, len);
+	fb_dealloc_cmap(&info->cmap);
+	framebuffer_release(info);
+	return 0;
+}
+
+
+/*
+ * Initialize the framebuffer.
+ */
+static const struct tc_device_id pmagbbfb_tc_table[] = {
+	{ "DEC     ", "PMAGB-BA" },
+	{ }
+};
+MODULE_DEVICE_TABLE(tc, pmagbbfb_tc_table);
+
+static struct tc_driver pmagbbfb_driver = {
+	.id_table	= pmagbbfb_tc_table,
+	.driver		= {
+		.name	= "pmagbbfb",
+		.bus	= &tc_bus_type,
+		.probe	= pmagbbfb_probe,
+		.remove	= pmagbbfb_remove,
+	},
+};
+
+static int __init pmagbbfb_init(void)
+{
+#ifndef MODULE
+	if (fb_get_options("pmagbbfb", NULL))
+		return -ENXIO;
+#endif
+	return tc_register_driver(&pmagbbfb_driver);
+}
+
+static void __exit pmagbbfb_exit(void)
+{
+	tc_unregister_driver(&pmagbbfb_driver);
+}
+
+
+module_init(pmagbbfb_init);
+module_exit(pmagbbfb_exit);
+
+MODULE_LICENSE("GPL");