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, 461 insertions, 0 deletions

diff --git a/drivers/mtd/tests/pagetest.c b/drivers/mtd/tests/pagetest.c
new file mode 100644
index 000000000..6878700d2
--- /dev/null
+++ b/drivers/mtd/tests/pagetest.c
@@ -0,0 +1,461 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2006-2008 Nokia Corporation
+ *
+ * Test page read and write on MTD device.
+ *
+ * Author: Adrian Hunter <ext-adrian.hunter@nokia.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <asm/div64.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/err.h>
+#include <linux/mtd/mtd.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/prandom.h>
+
+#include "mtd_test.h"
+
+static int dev = -EINVAL;
+module_param(dev, int, S_IRUGO);
+MODULE_PARM_DESC(dev, "MTD device number to use");
+
+static struct mtd_info *mtd;
+static unsigned char *twopages;
+static unsigned char *writebuf;
+static unsigned char *boundary;
+static unsigned char *bbt;
+
+static int pgsize;
+static int bufsize;
+static int ebcnt;
+static int pgcnt;
+static int errcnt;
+static struct rnd_state rnd_state;
+
+static int write_eraseblock(int ebnum)
+{
+	loff_t addr = (loff_t)ebnum * mtd->erasesize;
+
+	prandom_bytes_state(&rnd_state, writebuf, mtd->erasesize);
+	cond_resched();
+	return mtdtest_write(mtd, addr, mtd->erasesize, writebuf);
+}
+
+static int verify_eraseblock(int ebnum)
+{
+	uint32_t j;
+	int err = 0, i;
+	loff_t addr0, addrn;
+	loff_t addr = (loff_t)ebnum * mtd->erasesize;
+
+	addr0 = 0;
+	for (i = 0; i < ebcnt && bbt[i]; ++i)
+		addr0 += mtd->erasesize;
+
+	addrn = mtd->size;
+	for (i = 0; i < ebcnt && bbt[ebcnt - i - 1]; ++i)
+		addrn -= mtd->erasesize;
+
+	prandom_bytes_state(&rnd_state, writebuf, mtd->erasesize);
+	for (j = 0; j < pgcnt - 1; ++j, addr += pgsize) {
+		/* Do a read to set the internal dataRAMs to different data */
+		err = mtdtest_read(mtd, addr0, bufsize, twopages);
+		if (err)
+			return err;
+		err = mtdtest_read(mtd, addrn - bufsize, bufsize, twopages);
+		if (err)
+			return err;
+		memset(twopages, 0, bufsize);
+		err = mtdtest_read(mtd, addr, bufsize, twopages);
+		if (err)
+			break;
+		if (memcmp(twopages, writebuf + (j * pgsize), bufsize)) {
+			pr_err("error: verify failed at %#llx\n",
+			       (long long)addr);
+			errcnt += 1;
+		}
+	}
+	/* Check boundary between eraseblocks */
+	if (addr <= addrn - pgsize - pgsize && !bbt[ebnum + 1]) {
+		struct rnd_state old_state = rnd_state;
+
+		/* Do a read to set the internal dataRAMs to different data */
+		err = mtdtest_read(mtd, addr0, bufsize, twopages);
+		if (err)
+			return err;
+		err = mtdtest_read(mtd, addrn - bufsize, bufsize, twopages);
+		if (err)
+			return err;
+		memset(twopages, 0, bufsize);
+		err = mtdtest_read(mtd, addr, bufsize, twopages);
+		if (err)
+			return err;
+		memcpy(boundary, writebuf + mtd->erasesize - pgsize, pgsize);
+		prandom_bytes_state(&rnd_state, boundary + pgsize, pgsize);
+		if (memcmp(twopages, boundary, bufsize)) {
+			pr_err("error: verify failed at %#llx\n",
+			       (long long)addr);
+			errcnt += 1;
+		}
+		rnd_state = old_state;
+	}
+	return err;
+}
+
+static int crosstest(void)
+{
+	int err = 0, i;
+	loff_t addr, addr0, addrn;
+	unsigned char *pp1, *pp2, *pp3, *pp4;
+
+	pr_info("crosstest\n");
+	pp1 = kcalloc(pgsize, 4, GFP_KERNEL);
+	if (!pp1)
+		return -ENOMEM;
+	pp2 = pp1 + pgsize;
+	pp3 = pp2 + pgsize;
+	pp4 = pp3 + pgsize;
+
+	addr0 = 0;
+	for (i = 0; i < ebcnt && bbt[i]; ++i)
+		addr0 += mtd->erasesize;
+
+	addrn = mtd->size;
+	for (i = 0; i < ebcnt && bbt[ebcnt - i - 1]; ++i)
+		addrn -= mtd->erasesize;
+
+	/* Read 2nd-to-last page to pp1 */
+	addr = addrn - pgsize - pgsize;
+	err = mtdtest_read(mtd, addr, pgsize, pp1);
+	if (err) {
+		kfree(pp1);
+		return err;
+	}
+
+	/* Read 3rd-to-last page to pp1 */
+	addr = addrn - pgsize - pgsize - pgsize;
+	err = mtdtest_read(mtd, addr, pgsize, pp1);
+	if (err) {
+		kfree(pp1);
+		return err;
+	}
+
+	/* Read first page to pp2 */
+	addr = addr0;
+	pr_info("reading page at %#llx\n", (long long)addr);
+	err = mtdtest_read(mtd, addr, pgsize, pp2);
+	if (err) {
+		kfree(pp1);
+		return err;
+	}
+
+	/* Read last page to pp3 */
+	addr = addrn - pgsize;
+	pr_info("reading page at %#llx\n", (long long)addr);
+	err = mtdtest_read(mtd, addr, pgsize, pp3);
+	if (err) {
+		kfree(pp1);
+		return err;
+	}
+
+	/* Read first page again to pp4 */
+	addr = addr0;
+	pr_info("reading page at %#llx\n", (long long)addr);
+	err = mtdtest_read(mtd, addr, pgsize, pp4);
+	if (err) {
+		kfree(pp1);
+		return err;
+	}
+
+	/* pp2 and pp4 should be the same */
+	pr_info("verifying pages read at %#llx match\n",
+	       (long long)addr0);
+	if (memcmp(pp2, pp4, pgsize)) {
+		pr_err("verify failed!\n");
+		errcnt += 1;
+	} else if (!err)
+		pr_info("crosstest ok\n");
+	kfree(pp1);
+	return err;
+}
+
+static int erasecrosstest(void)
+{
+	int err = 0, i, ebnum, ebnum2;
+	loff_t addr0;
+	char *readbuf = twopages;
+
+	pr_info("erasecrosstest\n");
+
+	ebnum = 0;
+	addr0 = 0;
+	for (i = 0; i < ebcnt && bbt[i]; ++i) {
+		addr0 += mtd->erasesize;
+		ebnum += 1;
+	}
+
+	ebnum2 = ebcnt - 1;
+	while (ebnum2 && bbt[ebnum2])
+		ebnum2 -= 1;
+
+	pr_info("erasing block %d\n", ebnum);
+	err = mtdtest_erase_eraseblock(mtd, ebnum);
+	if (err)
+		return err;
+
+	pr_info("writing 1st page of block %d\n", ebnum);
+	prandom_bytes_state(&rnd_state, writebuf, pgsize);
+	strcpy(writebuf, "There is no data like this!");
+	err = mtdtest_write(mtd, addr0, pgsize, writebuf);
+	if (err)
+		return err;
+
+	pr_info("reading 1st page of block %d\n", ebnum);
+	memset(readbuf, 0, pgsize);
+	err = mtdtest_read(mtd, addr0, pgsize, readbuf);
+	if (err)
+		return err;
+
+	pr_info("verifying 1st page of block %d\n", ebnum);
+	if (memcmp(writebuf, readbuf, pgsize)) {
+		pr_err("verify failed!\n");
+		errcnt += 1;
+		return -1;
+	}
+
+	pr_info("erasing block %d\n", ebnum);
+	err = mtdtest_erase_eraseblock(mtd, ebnum);
+	if (err)
+		return err;
+
+	pr_info("writing 1st page of block %d\n", ebnum);
+	prandom_bytes_state(&rnd_state, writebuf, pgsize);
+	strcpy(writebuf, "There is no data like this!");
+	err = mtdtest_write(mtd, addr0, pgsize, writebuf);
+	if (err)
+		return err;
+
+	pr_info("erasing block %d\n", ebnum2);
+	err = mtdtest_erase_eraseblock(mtd, ebnum2);
+	if (err)
+		return err;
+
+	pr_info("reading 1st page of block %d\n", ebnum);
+	memset(readbuf, 0, pgsize);
+	err = mtdtest_read(mtd, addr0, pgsize, readbuf);
+	if (err)
+		return err;
+
+	pr_info("verifying 1st page of block %d\n", ebnum);
+	if (memcmp(writebuf, readbuf, pgsize)) {
+		pr_err("verify failed!\n");
+		errcnt += 1;
+		return -1;
+	}
+
+	if (!err)
+		pr_info("erasecrosstest ok\n");
+	return err;
+}
+
+static int erasetest(void)
+{
+	int err = 0, i, ebnum, ok = 1;
+	loff_t addr0;
+
+	pr_info("erasetest\n");
+
+	ebnum = 0;
+	addr0 = 0;
+	for (i = 0; i < ebcnt && bbt[i]; ++i) {
+		addr0 += mtd->erasesize;
+		ebnum += 1;
+	}
+
+	pr_info("erasing block %d\n", ebnum);
+	err = mtdtest_erase_eraseblock(mtd, ebnum);
+	if (err)
+		return err;
+
+	pr_info("writing 1st page of block %d\n", ebnum);
+	prandom_bytes_state(&rnd_state, writebuf, pgsize);
+	err = mtdtest_write(mtd, addr0, pgsize, writebuf);
+	if (err)
+		return err;
+
+	pr_info("erasing block %d\n", ebnum);
+	err = mtdtest_erase_eraseblock(mtd, ebnum);
+	if (err)
+		return err;
+
+	pr_info("reading 1st page of block %d\n", ebnum);
+	err = mtdtest_read(mtd, addr0, pgsize, twopages);
+	if (err)
+		return err;
+
+	pr_info("verifying 1st page of block %d is all 0xff\n",
+	       ebnum);
+	for (i = 0; i < pgsize; ++i)
+		if (twopages[i] != 0xff) {
+			pr_err("verifying all 0xff failed at %d\n",
+			       i);
+			errcnt += 1;
+			ok = 0;
+			break;
+		}
+
+	if (ok && !err)
+		pr_info("erasetest ok\n");
+
+	return err;
+}
+
+static int __init mtd_pagetest_init(void)
+{
+	int err = 0;
+	uint64_t tmp;
+	uint32_t i;
+
+	printk(KERN_INFO "\n");
+	printk(KERN_INFO "=================================================\n");
+
+	if (dev < 0) {
+		pr_info("Please specify a valid mtd-device via module parameter\n");
+		pr_crit("CAREFUL: This test wipes all data on the specified MTD device!\n");
+		return -EINVAL;
+	}
+
+	pr_info("MTD device: %d\n", dev);
+
+	mtd = get_mtd_device(NULL, dev);
+	if (IS_ERR(mtd)) {
+		err = PTR_ERR(mtd);
+		pr_err("error: cannot get MTD device\n");
+		return err;
+	}
+
+	if (!mtd_type_is_nand(mtd)) {
+		pr_info("this test requires NAND flash\n");
+		goto out;
+	}
+
+	tmp = mtd->size;
+	do_div(tmp, mtd->erasesize);
+	ebcnt = tmp;
+	pgcnt = mtd->erasesize / mtd->writesize;
+	pgsize = mtd->writesize;
+
+	pr_info("MTD device size %llu, eraseblock size %u, "
+	       "page size %u, count of eraseblocks %u, pages per "
+	       "eraseblock %u, OOB size %u\n",
+	       (unsigned long long)mtd->size, mtd->erasesize,
+	       pgsize, ebcnt, pgcnt, mtd->oobsize);
+
+	err = -ENOMEM;
+	bufsize = pgsize * 2;
+	writebuf = kmalloc(mtd->erasesize, GFP_KERNEL);
+	if (!writebuf)
+		goto out;
+	twopages = kmalloc(bufsize, GFP_KERNEL);
+	if (!twopages)
+		goto out;
+	boundary = kmalloc(bufsize, GFP_KERNEL);
+	if (!boundary)
+		goto out;
+
+	bbt = kzalloc(ebcnt, GFP_KERNEL);
+	if (!bbt)
+		goto out;
+	err = mtdtest_scan_for_bad_eraseblocks(mtd, bbt, 0, ebcnt);
+	if (err)
+		goto out;
+
+	/* Erase all eraseblocks */
+	pr_info("erasing whole device\n");
+	err = mtdtest_erase_good_eraseblocks(mtd, bbt, 0, ebcnt);
+	if (err)
+		goto out;
+	pr_info("erased %u eraseblocks\n", ebcnt);
+
+	/* Write all eraseblocks */
+	prandom_seed_state(&rnd_state, 1);
+	pr_info("writing whole device\n");
+	for (i = 0; i < ebcnt; ++i) {
+		if (bbt[i])
+			continue;
+		err = write_eraseblock(i);
+		if (err)
+			goto out;
+		if (i % 256 == 0)
+			pr_info("written up to eraseblock %u\n", i);
+
+		err = mtdtest_relax();
+		if (err)
+			goto out;
+	}
+	pr_info("written %u eraseblocks\n", i);
+
+	/* Check all eraseblocks */
+	prandom_seed_state(&rnd_state, 1);
+	pr_info("verifying all eraseblocks\n");
+	for (i = 0; i < ebcnt; ++i) {
+		if (bbt[i])
+			continue;
+		err = verify_eraseblock(i);
+		if (err)
+			goto out;
+		if (i % 256 == 0)
+			pr_info("verified up to eraseblock %u\n", i);
+
+		err = mtdtest_relax();
+		if (err)
+			goto out;
+	}
+	pr_info("verified %u eraseblocks\n", i);
+
+	err = crosstest();
+	if (err)
+		goto out;
+
+	if (ebcnt > 1) {
+		err = erasecrosstest();
+		if (err)
+			goto out;
+	} else {
+		pr_info("skipping erasecrosstest, 2 erase blocks needed\n");
+	}
+
+	err = erasetest();
+	if (err)
+		goto out;
+
+	pr_info("finished with %d errors\n", errcnt);
+out:
+
+	kfree(bbt);
+	kfree(boundary);
+	kfree(twopages);
+	kfree(writebuf);
+	put_mtd_device(mtd);
+	if (err)
+		pr_info("error %d occurred\n", err);
+	printk(KERN_INFO "=================================================\n");
+	return err;
+}
+module_init(mtd_pagetest_init);
+
+static void __exit mtd_pagetest_exit(void)
+{
+	return;
+}
+module_exit(mtd_pagetest_exit);
+
+MODULE_DESCRIPTION("NAND page test");
+MODULE_AUTHOR("Adrian Hunter");
+MODULE_LICENSE("GPL");