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, 254 insertions, 0 deletions

diff --git a/crypto/algboss.c b/crypto/algboss.c
new file mode 100644
index 000000000..8b936cae6
--- /dev/null
+++ b/crypto/algboss.c
@@ -0,0 +1,254 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Create default crypto algorithm instances.
+ *
+ * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <crypto/internal/aead.h>
+#include <linux/completion.h>
+#include <linux/ctype.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/rtnetlink.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include "internal.h"
+
+struct cryptomgr_param {
+	struct rtattr *tb[CRYPTO_MAX_ATTRS + 2];
+
+	struct {
+		struct rtattr attr;
+		struct crypto_attr_type data;
+	} type;
+
+	struct {
+		struct rtattr attr;
+		struct crypto_attr_alg data;
+	} attrs[CRYPTO_MAX_ATTRS];
+
+	char template[CRYPTO_MAX_ALG_NAME];
+
+	struct crypto_larval *larval;
+
+	u32 otype;
+	u32 omask;
+};
+
+struct crypto_test_param {
+	char driver[CRYPTO_MAX_ALG_NAME];
+	char alg[CRYPTO_MAX_ALG_NAME];
+	u32 type;
+};
+
+static int cryptomgr_probe(void *data)
+{
+	struct cryptomgr_param *param = data;
+	struct crypto_template *tmpl;
+	int err = -ENOENT;
+
+	tmpl = crypto_lookup_template(param->template);
+	if (!tmpl)
+		goto out;
+
+	do {
+		err = tmpl->create(tmpl, param->tb);
+	} while (err == -EAGAIN && !signal_pending(current));
+
+	crypto_tmpl_put(tmpl);
+
+out:
+	param->larval->adult = ERR_PTR(err);
+	param->larval->alg.cra_flags |= CRYPTO_ALG_DEAD;
+	complete_all(&param->larval->completion);
+	crypto_alg_put(&param->larval->alg);
+	kfree(param);
+	module_put_and_kthread_exit(0);
+}
+
+static int cryptomgr_schedule_probe(struct crypto_larval *larval)
+{
+	struct task_struct *thread;
+	struct cryptomgr_param *param;
+	const char *name = larval->alg.cra_name;
+	const char *p;
+	unsigned int len;
+	int i;
+
+	if (!try_module_get(THIS_MODULE))
+		goto err;
+
+	param = kzalloc_obj(*param);
+	if (!param)
+		goto err_put_module;
+
+	for (p = name; isalnum(*p) || *p == '-' || *p == '_'; p++)
+		;
+
+	len = p - name;
+	if (!len || *p != '(')
+		goto err_free_param;
+
+	memcpy(param->template, name, len);
+
+	i = 0;
+	for (;;) {
+		name = ++p;
+
+		for (; isalnum(*p) || *p == '-' || *p == '_'; p++)
+			;
+
+		if (*p == '(') {
+			int recursion = 0;
+
+			for (;;) {
+				if (!*++p)
+					goto err_free_param;
+				if (*p == '(')
+					recursion++;
+				else if (*p == ')' && !recursion--)
+					break;
+			}
+
+			p++;
+		}
+
+		len = p - name;
+		if (!len)
+			goto err_free_param;
+
+		param->attrs[i].attr.rta_len = sizeof(param->attrs[i]);
+		param->attrs[i].attr.rta_type = CRYPTOA_ALG;
+		memcpy(param->attrs[i].data.name, name, len);
+
+		param->tb[i + 1] = &param->attrs[i].attr;
+		i++;
+
+		if (i >= CRYPTO_MAX_ATTRS)
+			goto err_free_param;
+
+		if (*p == ')')
+			break;
+
+		if (*p != ',')
+			goto err_free_param;
+	}
+
+	param->tb[i + 1] = NULL;
+
+	param->type.attr.rta_len = sizeof(param->type);
+	param->type.attr.rta_type = CRYPTOA_TYPE;
+	param->type.data.type = larval->alg.cra_flags & ~CRYPTO_ALG_TESTED;
+	param->type.data.mask = larval->mask & ~CRYPTO_ALG_TESTED;
+	param->tb[0] = &param->type.attr;
+
+	param->otype = larval->alg.cra_flags;
+	param->omask = larval->mask;
+
+	crypto_alg_get(&larval->alg);
+	param->larval = larval;
+
+	thread = kthread_run(cryptomgr_probe, param, "cryptomgr_probe");
+	if (IS_ERR(thread))
+		goto err_put_larval;
+
+	return NOTIFY_STOP;
+
+err_put_larval:
+	crypto_alg_put(&larval->alg);
+err_free_param:
+	kfree(param);
+err_put_module:
+	module_put(THIS_MODULE);
+err:
+	return NOTIFY_OK;
+}
+
+static int cryptomgr_test(void *data)
+{
+	struct crypto_test_param *param = data;
+	u32 type = param->type;
+	int err;
+
+	err = alg_test(param->driver, param->alg, type, CRYPTO_ALG_TESTED);
+
+	crypto_alg_tested(param->driver, err);
+
+	kfree(param);
+	module_put_and_kthread_exit(0);
+}
+
+static int cryptomgr_schedule_test(struct crypto_alg *alg)
+{
+	struct task_struct *thread;
+	struct crypto_test_param *param;
+
+	if (!IS_ENABLED(CONFIG_CRYPTO_SELFTESTS))
+		return NOTIFY_DONE;
+
+	if (!try_module_get(THIS_MODULE))
+		goto err;
+
+	param = kzalloc_obj(*param);
+	if (!param)
+		goto err_put_module;
+
+	memcpy(param->driver, alg->cra_driver_name, sizeof(param->driver));
+	memcpy(param->alg, alg->cra_name, sizeof(param->alg));
+	param->type = alg->cra_flags;
+
+	thread = kthread_run(cryptomgr_test, param, "cryptomgr_test");
+	if (IS_ERR(thread))
+		goto err_free_param;
+
+	return NOTIFY_STOP;
+
+err_free_param:
+	kfree(param);
+err_put_module:
+	module_put(THIS_MODULE);
+err:
+	return NOTIFY_OK;
+}
+
+static int cryptomgr_notify(struct notifier_block *this, unsigned long msg,
+			    void *data)
+{
+	switch (msg) {
+	case CRYPTO_MSG_ALG_REQUEST:
+		return cryptomgr_schedule_probe(data);
+	case CRYPTO_MSG_ALG_REGISTER:
+		return cryptomgr_schedule_test(data);
+	case CRYPTO_MSG_ALG_LOADED:
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block cryptomgr_notifier = {
+	.notifier_call = cryptomgr_notify,
+};
+
+static int __init cryptomgr_init(void)
+{
+	return crypto_register_notifier(&cryptomgr_notifier);
+}
+
+static void __exit cryptomgr_exit(void)
+{
+	int err = crypto_unregister_notifier(&cryptomgr_notifier);
+	BUG_ON(err);
+}
+
+module_init(cryptomgr_init);
+module_exit(cryptomgr_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Crypto Algorithm Manager");