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, 385 insertions, 0 deletions

diff --git a/scripts/dtc/dtc.c b/scripts/dtc/dtc.c
new file mode 100644
index 000000000..6dae60de0
--- /dev/null
+++ b/scripts/dtc/dtc.c
@@ -0,0 +1,385 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * (C) Copyright David Gibson <dwg@au1.ibm.com>, IBM Corporation.  2005.
+ */
+
+#include <sys/stat.h>
+
+#include "dtc.h"
+#include "srcpos.h"
+
+/*
+ * Command line options
+ */
+int quiet;		/* Level of quietness */
+unsigned int reservenum;/* Number of memory reservation slots */
+int minsize;		/* Minimum blob size */
+int padsize;		/* Additional padding to blob */
+int alignsize;		/* Additional padding to blob according to the alignsize */
+int phandle_format = PHANDLE_EPAPR;	/* Use linux,phandle or phandle properties */
+int generate_symbols;	/* enable symbols & fixup support */
+int generate_fixups;		/* suppress generation of fixups on symbol support */
+int auto_label_aliases;		/* auto generate labels -> aliases */
+int annotate;		/* Level of annotation: 1 for input source location
+			   >1 for full input source location. */
+
+static int is_power_of_2(int x)
+{
+	return (x > 0) && ((x & (x - 1)) == 0);
+}
+
+static void fill_fullpaths(struct node *tree, const char *prefix)
+{
+	struct node *child;
+	const char *unit;
+
+	tree->fullpath = join_path(prefix, tree->name);
+
+	unit = strchr(tree->name, '@');
+	if (unit)
+		tree->basenamelen = unit - tree->name;
+	else
+		tree->basenamelen = strlen(tree->name);
+
+	for_each_child(tree, child)
+		fill_fullpaths(child, tree->fullpath);
+}
+
+/* Usage related data. */
+static const char usage_synopsis[] = "dtc [options] <input file>";
+static const char usage_short_opts[] = "qI:O:o:V:d:R:S:p:a:fb:i:H:sW:E:@LAThv";
+static struct option const usage_long_opts[] = {
+	{"quiet",            no_argument, NULL, 'q'},
+	{"in-format",         a_argument, NULL, 'I'},
+	{"out",               a_argument, NULL, 'o'},
+	{"out-format",        a_argument, NULL, 'O'},
+	{"out-version",       a_argument, NULL, 'V'},
+	{"out-dependency",    a_argument, NULL, 'd'},
+	{"reserve",           a_argument, NULL, 'R'},
+	{"space",             a_argument, NULL, 'S'},
+	{"pad",               a_argument, NULL, 'p'},
+	{"align",             a_argument, NULL, 'a'},
+	{"boot-cpu",          a_argument, NULL, 'b'},
+	{"force",            no_argument, NULL, 'f'},
+	{"include",           a_argument, NULL, 'i'},
+	{"sort",             no_argument, NULL, 's'},
+	{"phandle",           a_argument, NULL, 'H'},
+	{"warning",           a_argument, NULL, 'W'},
+	{"error",             a_argument, NULL, 'E'},
+	{"symbols",	     no_argument, NULL, '@'},
+	{"local-fixups",     no_argument, NULL, 'L'},
+	{"auto-alias",       no_argument, NULL, 'A'},
+	{"annotate",         no_argument, NULL, 'T'},
+	{"help",             no_argument, NULL, 'h'},
+	{"version",          no_argument, NULL, 'v'},
+	{NULL,               no_argument, NULL, 0x0},
+};
+static const char * const usage_opts_help[] = {
+	"\n\tQuiet: -q suppress warnings, -qq errors, -qqq all",
+	"\n\tInput formats are:\n"
+	 "\t\tdts - device tree source text\n"
+	 "\t\tdtb - device tree blob\n"
+	 "\t\tfs  - /proc/device-tree style directory",
+	"\n\tOutput file",
+	"\n\tOutput formats are:\n"
+	 "\t\tdts - device tree source text\n"
+	 "\t\tdtb - device tree blob\n"
+#ifndef NO_YAML
+	 "\t\tyaml - device tree encoded as YAML\n"
+#endif
+	 "\t\tasm - assembler source",
+	"\n\tBlob version to produce, defaults to "stringify(DEFAULT_FDT_VERSION)" (for dtb and asm output)",
+	"\n\tOutput dependency file",
+	"\n\tMake space for <number> reserve map entries (for dtb and asm output)",
+	"\n\tMake the blob at least <bytes> long (extra space)",
+	"\n\tAdd padding to the blob of <bytes> long (extra space)",
+	"\n\tMake the blob align to the <bytes> (extra space)",
+	"\n\tSet the physical boot cpu",
+	"\n\tTry to produce output even if the input tree has errors",
+	"\n\tAdd a path to search for include files",
+	"\n\tSort nodes and properties before outputting (useful for comparing trees)",
+	"\n\tValid phandle formats are:\n"
+	 "\t\tlegacy - \"linux,phandle\" properties only\n"
+	 "\t\tepapr  - \"phandle\" properties only\n"
+	 "\t\tboth   - Both \"linux,phandle\" and \"phandle\" properties",
+	"\n\tEnable/disable warnings (prefix with \"no-\")",
+	"\n\tEnable/disable errors (prefix with \"no-\")",
+	"\n\tEnable generation of symbols",
+	"\n\tPossibly generates a __local_fixups__ and a __fixups__ node at the root node",
+	"\n\tEnable auto-alias of labels",
+	"\n\tAnnotate output .dts with input source file and line (-T -T for more details)",
+	"\n\tPrint this help and exit",
+	"\n\tPrint version and exit",
+	NULL,
+};
+
+static const char *guess_type_by_name(const char *fname, const char *fallback)
+{
+	const char *s;
+
+	s = strrchr(fname, '.');
+	if (s == NULL)
+		return fallback;
+	if (!strcasecmp(s, ".dts"))
+		return "dts";
+	if (!strcasecmp(s, ".yaml"))
+		return "yaml";
+	if (!strcasecmp(s, ".dtbo"))
+		return "dtb";
+	if (!strcasecmp(s, ".dtb"))
+		return "dtb";
+	return fallback;
+}
+
+static const char *guess_input_format(const char *fname, const char *fallback)
+{
+	struct stat statbuf;
+	fdt32_t magic;
+	FILE *f;
+
+	if (stat(fname, &statbuf) != 0)
+		return fallback;
+
+	if (S_ISDIR(statbuf.st_mode))
+		return "fs";
+
+	if (!S_ISREG(statbuf.st_mode))
+		return fallback;
+
+	f = fopen(fname, "r");
+	if (f == NULL)
+		return fallback;
+	if (fread(&magic, 4, 1, f) != 1) {
+		fclose(f);
+		return fallback;
+	}
+	fclose(f);
+
+	if (fdt32_to_cpu(magic) == FDT_MAGIC)
+		return "dtb";
+
+	return guess_type_by_name(fname, fallback);
+}
+
+int main(int argc, char *argv[])
+{
+	struct dt_info *dti;
+	const char *inform = NULL;
+	const char *outform = NULL;
+	const char *outname = "-";
+	const char *depname = NULL;
+	bool force = false, sort = false;
+	const char *arg;
+	int opt;
+	FILE *outf = NULL;
+	int outversion = DEFAULT_FDT_VERSION;
+	long long cmdline_boot_cpuid = -1;
+
+	quiet      = 0;
+	reservenum = 0;
+	minsize    = 0;
+	padsize    = 0;
+	alignsize  = 0;
+
+	while ((opt = util_getopt_long()) != EOF) {
+		switch (opt) {
+		case 'I':
+			inform = optarg;
+			break;
+		case 'O':
+			outform = optarg;
+			break;
+		case 'o':
+			outname = optarg;
+			break;
+		case 'V':
+			outversion = strtol(optarg, NULL, 0);
+			break;
+		case 'd':
+			depname = optarg;
+			break;
+		case 'R':
+			reservenum = strtoul(optarg, NULL, 0);
+			break;
+		case 'S':
+			minsize = strtol(optarg, NULL, 0);
+			break;
+		case 'p':
+			padsize = strtol(optarg, NULL, 0);
+			break;
+		case 'a':
+			alignsize = strtol(optarg, NULL, 0);
+			if (!is_power_of_2(alignsize))
+				die("Invalid argument \"%d\" to -a option\n",
+				    alignsize);
+			break;
+		case 'f':
+			force = true;
+			break;
+		case 'q':
+			quiet++;
+			break;
+		case 'b':
+			cmdline_boot_cpuid = strtoll(optarg, NULL, 0);
+			break;
+		case 'i':
+			srcfile_add_search_path(optarg);
+			break;
+		case 'v':
+			util_version();
+		case 'H':
+			if (streq(optarg, "legacy"))
+				phandle_format = PHANDLE_LEGACY;
+			else if (streq(optarg, "epapr"))
+				phandle_format = PHANDLE_EPAPR;
+			else if (streq(optarg, "both"))
+				phandle_format = PHANDLE_BOTH;
+			else
+				die("Invalid argument \"%s\" to -H option\n",
+				    optarg);
+			break;
+
+		case 's':
+			sort = true;
+			break;
+
+		case 'W':
+			parse_checks_option(true, false, optarg);
+			break;
+
+		case 'E':
+			parse_checks_option(false, true, optarg);
+			break;
+
+		case '@':
+			generate_symbols = 1;
+			break;
+
+		case 'L':
+			generate_fixups = 1;
+			break;
+
+		case 'A':
+			auto_label_aliases = 1;
+			break;
+		case 'T':
+			annotate++;
+			break;
+
+		case 'h':
+			usage(NULL);
+		default:
+			usage("unknown option");
+		}
+	}
+
+	if (argc > (optind+1))
+		usage("missing files");
+	else if (argc < (optind+1))
+		arg = "-";
+	else
+		arg = argv[optind];
+
+	/* minsize and padsize are mutually exclusive */
+	if (minsize && padsize)
+		die("Can't set both -p and -S\n");
+
+	if (depname) {
+		depfile = fopen(depname, "w");
+		if (!depfile)
+			die("Couldn't open dependency file %s: %s\n", depname,
+			    strerror(errno));
+
+		fprint_path_escaped(depfile, outname);
+		fputc(':', depfile);
+	}
+
+	if (inform == NULL)
+		inform = guess_input_format(arg, "dts");
+	if (outform == NULL) {
+		outform = guess_type_by_name(outname, NULL);
+		if (outform == NULL) {
+			if (streq(inform, "dts"))
+				outform = "dtb";
+			else
+				outform = "dts";
+		}
+	}
+	if (annotate && (!streq(inform, "dts") || !streq(outform, "dts")))
+		die("--annotate requires -I dts -O dts\n");
+	if (streq(inform, "dts"))
+		dti = dt_from_source(arg);
+	else if (streq(inform, "fs"))
+		dti = dt_from_fs(arg);
+	else if(streq(inform, "dtb"))
+		dti = dt_from_blob(arg);
+	else
+		die("Unknown input format \"%s\"\n", inform);
+
+	dti->outname = outname;
+
+	if (depfile) {
+		fputc('\n', depfile);
+		fclose(depfile);
+	}
+
+	if (cmdline_boot_cpuid != -1)
+		dti->boot_cpuid_phys = cmdline_boot_cpuid;
+
+	fill_fullpaths(dti->dt, "");
+
+	/* on a plugin, generate by default */
+	if (dti->dtsflags & DTSF_PLUGIN) {
+		generate_fixups = 1;
+	}
+
+	process_checks(force, dti);
+
+	if (auto_label_aliases)
+		generate_label_tree(dti, "aliases", false);
+
+	generate_labels_from_tree(dti, "__symbols__");
+
+	if (generate_symbols)
+		generate_label_tree(dti, "__symbols__", true);
+
+	fixup_phandles(dti, "__fixups__");
+	local_fixup_phandles(dti, "__local_fixups__");
+
+	if (generate_fixups) {
+		generate_fixups_tree(dti, "__fixups__");
+		generate_local_fixups_tree(dti, "__local_fixups__");
+	}
+
+	if (sort)
+		sort_tree(dti);
+
+	if (streq(outname, "-")) {
+		outf = stdout;
+	} else {
+		outf = fopen(outname, "wb");
+		if (! outf)
+			die("Couldn't open output file %s: %s\n",
+			    outname, strerror(errno));
+	}
+
+	if (streq(outform, "dts")) {
+		dt_to_source(outf, dti);
+#ifndef NO_YAML
+	} else if (streq(outform, "yaml")) {
+		if (!streq(inform, "dts"))
+			die("YAML output format requires dts input format\n");
+		dt_to_yaml(outf, dti);
+#endif
+	} else if (streq(outform, "dtb")) {
+		dt_to_blob(outf, dti, outversion);
+	} else if (streq(outform, "asm")) {
+		dt_to_asm(outf, dti, outversion);
+	} else if (streq(outform, "null")) {
+		/* do nothing */
+	} else {
+		die("Unknown output format \"%s\"\n", outform);
+	}
+
+	exit(0);
+}