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, 306 insertions, 0 deletions

diff --git a/drivers/mtd/devices/ms02-nv.c b/drivers/mtd/devices/ms02-nv.c
new file mode 100644
index 000000000..453b3e05f
--- /dev/null
+++ b/drivers/mtd/devices/ms02-nv.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	Copyright (c) 2001 Maciej W. Rozycki
+ */
+
+#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include <asm/addrspace.h>
+#include <asm/bootinfo.h>
+#include <asm/dec/ioasic_addrs.h>
+#include <asm/dec/kn02.h>
+#include <asm/dec/kn03.h>
+#include <asm/io.h>
+#include <asm/paccess.h>
+
+#include "ms02-nv.h"
+
+
+static char version[] __initdata =
+	"ms02-nv.c: v.1.0.0  13 Aug 2001  Maciej W. Rozycki.\n";
+
+MODULE_AUTHOR("Maciej W. Rozycki <macro@linux-mips.org>");
+MODULE_DESCRIPTION("DEC MS02-NV NVRAM module driver");
+MODULE_LICENSE("GPL");
+
+
+/*
+ * Addresses we probe for an MS02-NV at.  Modules may be located
+ * at any 8MiB boundary within a 0MiB up to 112MiB range or at any 32MiB
+ * boundary within a 0MiB up to 448MiB range.  We don't support a module
+ * at 0MiB, though.
+ */
+static ulong ms02nv_addrs[] __initdata = {
+	0x07000000, 0x06800000, 0x06000000, 0x05800000, 0x05000000,
+	0x04800000, 0x04000000, 0x03800000, 0x03000000, 0x02800000,
+	0x02000000, 0x01800000, 0x01000000, 0x00800000
+};
+
+static const char ms02nv_name[] = "DEC MS02-NV NVRAM";
+static const char ms02nv_res_diag_ram[] = "Diagnostic RAM";
+static const char ms02nv_res_user_ram[] = "General-purpose RAM";
+static const char ms02nv_res_csr[] = "Control and status register";
+
+static struct mtd_info *root_ms02nv_mtd;
+
+
+static int ms02nv_read(struct mtd_info *mtd, loff_t from,
+			size_t len, size_t *retlen, u_char *buf)
+{
+	struct ms02nv_private *mp = mtd->priv;
+
+	memcpy(buf, mp->uaddr + from, len);
+	*retlen = len;
+	return 0;
+}
+
+static int ms02nv_write(struct mtd_info *mtd, loff_t to,
+			size_t len, size_t *retlen, const u_char *buf)
+{
+	struct ms02nv_private *mp = mtd->priv;
+
+	memcpy(mp->uaddr + to, buf, len);
+	*retlen = len;
+	return 0;
+}
+
+
+static inline uint ms02nv_probe_one(ulong addr)
+{
+	ms02nv_uint *ms02nv_diagp;
+	ms02nv_uint *ms02nv_magicp;
+	uint ms02nv_diag;
+	uint ms02nv_magic;
+	size_t size;
+
+	int err;
+
+	/*
+	 * The firmware writes MS02NV_ID at MS02NV_MAGIC and also
+	 * a diagnostic status at MS02NV_DIAG.
+	 */
+	ms02nv_diagp = (ms02nv_uint *)(CKSEG1ADDR(addr + MS02NV_DIAG));
+	ms02nv_magicp = (ms02nv_uint *)(CKSEG1ADDR(addr + MS02NV_MAGIC));
+	err = get_dbe(ms02nv_magic, ms02nv_magicp);
+	if (err)
+		return 0;
+	if (ms02nv_magic != MS02NV_ID)
+		return 0;
+
+	ms02nv_diag = *ms02nv_diagp;
+	size = (ms02nv_diag & MS02NV_DIAG_SIZE_MASK) << MS02NV_DIAG_SIZE_SHIFT;
+	if (size > MS02NV_CSR)
+		size = MS02NV_CSR;
+
+	return size;
+}
+
+static int __init ms02nv_init_one(ulong addr)
+{
+	struct mtd_info *mtd;
+	struct ms02nv_private *mp;
+	struct resource *mod_res;
+	struct resource *diag_res;
+	struct resource *user_res;
+	struct resource *csr_res;
+	ulong fixaddr;
+	size_t size, fixsize;
+
+	static int version_printed;
+
+	int ret = -ENODEV;
+
+	/* The module decodes 8MiB of address space. */
+	mod_res = kzalloc_obj(*mod_res);
+	if (!mod_res)
+		return -ENOMEM;
+
+	mod_res->name = ms02nv_name;
+	mod_res->start = addr;
+	mod_res->end = addr + MS02NV_SLOT_SIZE - 1;
+	mod_res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+	if (request_resource(&iomem_resource, mod_res) < 0)
+		goto err_out_mod_res;
+
+	size = ms02nv_probe_one(addr);
+	if (!size)
+		goto err_out_mod_res_rel;
+
+	if (!version_printed) {
+		printk(KERN_INFO "%s", version);
+		version_printed = 1;
+	}
+
+	ret = -ENOMEM;
+	mtd = kzalloc_obj(*mtd);
+	if (!mtd)
+		goto err_out_mod_res_rel;
+	mp = kzalloc_obj(*mp);
+	if (!mp)
+		goto err_out_mtd;
+
+	mtd->priv = mp;
+	mp->resource.module = mod_res;
+
+	/* Firmware's diagnostic NVRAM area. */
+	diag_res = kzalloc_obj(*diag_res);
+	if (!diag_res)
+		goto err_out_mp;
+
+	diag_res->name = ms02nv_res_diag_ram;
+	diag_res->start = addr;
+	diag_res->end = addr + MS02NV_RAM - 1;
+	diag_res->flags = IORESOURCE_BUSY;
+	request_resource(mod_res, diag_res);
+
+	mp->resource.diag_ram = diag_res;
+
+	/* User-available general-purpose NVRAM area. */
+	user_res = kzalloc_obj(*user_res);
+	if (!user_res)
+		goto err_out_diag_res;
+
+	user_res->name = ms02nv_res_user_ram;
+	user_res->start = addr + MS02NV_RAM;
+	user_res->end = addr + size - 1;
+	user_res->flags = IORESOURCE_BUSY;
+	request_resource(mod_res, user_res);
+
+	mp->resource.user_ram = user_res;
+
+	/* Control and status register. */
+	csr_res = kzalloc_obj(*csr_res);
+	if (!csr_res)
+		goto err_out_user_res;
+
+	csr_res->name = ms02nv_res_csr;
+	csr_res->start = addr + MS02NV_CSR;
+	csr_res->end = addr + MS02NV_CSR + 3;
+	csr_res->flags = IORESOURCE_BUSY;
+	request_resource(mod_res, csr_res);
+
+	mp->resource.csr = csr_res;
+
+	mp->addr = phys_to_virt(addr);
+	mp->size = size;
+
+	/*
+	 * Hide the firmware's diagnostic area.  It may get destroyed
+	 * upon a reboot.  Take paging into account for mapping support.
+	 */
+	fixaddr = (addr + MS02NV_RAM + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
+	fixsize = (size - (fixaddr - addr)) & ~(PAGE_SIZE - 1);
+	mp->uaddr = phys_to_virt(fixaddr);
+
+	mtd->type = MTD_RAM;
+	mtd->flags = MTD_CAP_RAM;
+	mtd->size = fixsize;
+	mtd->name = ms02nv_name;
+	mtd->owner = THIS_MODULE;
+	mtd->_read = ms02nv_read;
+	mtd->_write = ms02nv_write;
+	mtd->writesize = 1;
+
+	ret = -EIO;
+	if (mtd_device_register(mtd, NULL, 0)) {
+		printk(KERN_ERR
+			"ms02-nv: Unable to register MTD device, aborting!\n");
+		goto err_out_csr_res;
+	}
+
+	printk(KERN_INFO "mtd%d: %s at 0x%08lx, size %zuMiB.\n",
+		mtd->index, ms02nv_name, addr, size >> 20);
+
+	mp->next = root_ms02nv_mtd;
+	root_ms02nv_mtd = mtd;
+
+	return 0;
+
+
+err_out_csr_res:
+	release_resource(csr_res);
+	kfree(csr_res);
+err_out_user_res:
+	release_resource(user_res);
+	kfree(user_res);
+err_out_diag_res:
+	release_resource(diag_res);
+	kfree(diag_res);
+err_out_mp:
+	kfree(mp);
+err_out_mtd:
+	kfree(mtd);
+err_out_mod_res_rel:
+	release_resource(mod_res);
+err_out_mod_res:
+	kfree(mod_res);
+	return ret;
+}
+
+static void __exit ms02nv_remove_one(void)
+{
+	struct mtd_info *mtd = root_ms02nv_mtd;
+	struct ms02nv_private *mp = mtd->priv;
+
+	root_ms02nv_mtd = mp->next;
+
+	mtd_device_unregister(mtd);
+
+	release_resource(mp->resource.csr);
+	kfree(mp->resource.csr);
+	release_resource(mp->resource.user_ram);
+	kfree(mp->resource.user_ram);
+	release_resource(mp->resource.diag_ram);
+	kfree(mp->resource.diag_ram);
+	release_resource(mp->resource.module);
+	kfree(mp->resource.module);
+	kfree(mp);
+	kfree(mtd);
+}
+
+
+static int __init ms02nv_init(void)
+{
+	volatile u32 *csr;
+	uint stride = 0;
+	int count = 0;
+	int i;
+
+	switch (mips_machtype) {
+	case MACH_DS5000_200:
+		csr = (volatile u32 *)CKSEG1ADDR(KN02_SLOT_BASE + KN02_CSR);
+		if (*csr & KN02_CSR_BNK32M)
+			stride = 2;
+		break;
+	case MACH_DS5000_2X0:
+	case MACH_DS5900:
+		csr = (volatile u32 *)CKSEG1ADDR(KN03_SLOT_BASE + IOASIC_MCR);
+		if (*csr & KN03_MCR_BNK32M)
+			stride = 2;
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(ms02nv_addrs); i++)
+		if (!ms02nv_init_one(ms02nv_addrs[i] << stride))
+			count++;
+
+	return (count > 0) ? 0 : -ENODEV;
+}
+
+static void __exit ms02nv_cleanup(void)
+{
+	while (root_ms02nv_mtd)
+		ms02nv_remove_one();
+}
+
+
+module_init(ms02nv_init);
+module_exit(ms02nv_cleanup);