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, 394 insertions, 0 deletions

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
new file mode 100644
index 000000000..9f3724429
--- /dev/null
+++ b/crypto/pcrypt.c
@@ -0,0 +1,394 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * pcrypt - Parallel crypto wrapper.
+ *
+ * Copyright (C) 2009 secunet Security Networks AG
+ * Copyright (C) 2009 Steffen Klassert <steffen.klassert@secunet.com>
+ */
+
+#include <crypto/algapi.h>
+#include <crypto/internal/aead.h>
+#include <linux/atomic.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/kobject.h>
+#include <linux/cpu.h>
+#include <crypto/pcrypt.h>
+
+static struct padata_instance *pencrypt;
+static struct padata_instance *pdecrypt;
+static struct kset           *pcrypt_kset;
+
+struct pcrypt_instance_ctx {
+	struct crypto_aead_spawn spawn;
+	struct padata_shell *psenc;
+	struct padata_shell *psdec;
+	atomic_t tfm_count;
+};
+
+struct pcrypt_aead_ctx {
+	struct crypto_aead *child;
+	unsigned int cb_cpu;
+};
+
+static inline struct pcrypt_instance_ctx *pcrypt_tfm_ictx(
+	struct crypto_aead *tfm)
+{
+	return aead_instance_ctx(aead_alg_instance(tfm));
+}
+
+static int pcrypt_aead_setkey(struct crypto_aead *parent,
+			      const u8 *key, unsigned int keylen)
+{
+	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(parent);
+
+	return crypto_aead_setkey(ctx->child, key, keylen);
+}
+
+static int pcrypt_aead_setauthsize(struct crypto_aead *parent,
+				   unsigned int authsize)
+{
+	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(parent);
+
+	return crypto_aead_setauthsize(ctx->child, authsize);
+}
+
+static void pcrypt_aead_serial(struct padata_priv *padata)
+{
+	struct pcrypt_request *preq = pcrypt_padata_request(padata);
+	struct aead_request *req = pcrypt_request_ctx(preq);
+
+	aead_request_complete(req->base.data, padata->info);
+}
+
+static void pcrypt_aead_done(void *data, int err)
+{
+	struct aead_request *req = data;
+	struct pcrypt_request *preq = aead_request_ctx(req);
+	struct padata_priv *padata = pcrypt_request_padata(preq);
+
+	if (err == -EINPROGRESS)
+		return;
+
+	padata->info = err;
+
+	padata_do_serial(padata);
+}
+
+static void pcrypt_aead_enc(struct padata_priv *padata)
+{
+	struct pcrypt_request *preq = pcrypt_padata_request(padata);
+	struct aead_request *req = pcrypt_request_ctx(preq);
+	int ret;
+
+	ret = crypto_aead_encrypt(req);
+
+	if (ret == -EINPROGRESS || ret == -EBUSY)
+		return;
+
+	padata->info = ret;
+	padata_do_serial(padata);
+}
+
+static int pcrypt_aead_encrypt(struct aead_request *req)
+{
+	int err;
+	struct pcrypt_request *preq = aead_request_ctx(req);
+	struct aead_request *creq = pcrypt_request_ctx(preq);
+	struct padata_priv *padata = pcrypt_request_padata(preq);
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(aead);
+	u32 flags = aead_request_flags(req);
+	struct pcrypt_instance_ctx *ictx;
+
+	ictx = pcrypt_tfm_ictx(aead);
+
+	memset(padata, 0, sizeof(struct padata_priv));
+
+	padata->parallel = pcrypt_aead_enc;
+	padata->serial = pcrypt_aead_serial;
+
+	aead_request_set_tfm(creq, ctx->child);
+	aead_request_set_callback(creq, flags & ~CRYPTO_TFM_REQ_MAY_SLEEP,
+				  pcrypt_aead_done, req);
+	aead_request_set_crypt(creq, req->src, req->dst,
+			       req->cryptlen, req->iv);
+	aead_request_set_ad(creq, req->assoclen);
+
+	err = padata_do_parallel(ictx->psenc, padata, &ctx->cb_cpu);
+	if (!err)
+		return -EINPROGRESS;
+	if (err == -EBUSY) {
+		/* try non-parallel mode */
+		aead_request_set_callback(creq, flags, req->base.complete,
+					  req->base.data);
+		return crypto_aead_encrypt(creq);
+	}
+
+	return err;
+}
+
+static void pcrypt_aead_dec(struct padata_priv *padata)
+{
+	struct pcrypt_request *preq = pcrypt_padata_request(padata);
+	struct aead_request *req = pcrypt_request_ctx(preq);
+	int ret;
+
+	ret = crypto_aead_decrypt(req);
+
+	if (ret == -EINPROGRESS || ret == -EBUSY)
+		return;
+
+	padata->info = ret;
+	padata_do_serial(padata);
+}
+
+static int pcrypt_aead_decrypt(struct aead_request *req)
+{
+	int err;
+	struct pcrypt_request *preq = aead_request_ctx(req);
+	struct aead_request *creq = pcrypt_request_ctx(preq);
+	struct padata_priv *padata = pcrypt_request_padata(preq);
+	struct crypto_aead *aead = crypto_aead_reqtfm(req);
+	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(aead);
+	u32 flags = aead_request_flags(req);
+	struct pcrypt_instance_ctx *ictx;
+
+	ictx = pcrypt_tfm_ictx(aead);
+
+	memset(padata, 0, sizeof(struct padata_priv));
+
+	padata->parallel = pcrypt_aead_dec;
+	padata->serial = pcrypt_aead_serial;
+
+	aead_request_set_tfm(creq, ctx->child);
+	aead_request_set_callback(creq, flags & ~CRYPTO_TFM_REQ_MAY_SLEEP,
+				  pcrypt_aead_done, req);
+	aead_request_set_crypt(creq, req->src, req->dst,
+			       req->cryptlen, req->iv);
+	aead_request_set_ad(creq, req->assoclen);
+
+	err = padata_do_parallel(ictx->psdec, padata, &ctx->cb_cpu);
+	if (!err)
+		return -EINPROGRESS;
+	if (err == -EBUSY) {
+		/* try non-parallel mode */
+		aead_request_set_callback(creq, flags, req->base.complete,
+					  req->base.data);
+		return crypto_aead_decrypt(creq);
+	}
+
+	return err;
+}
+
+static int pcrypt_aead_init_tfm(struct crypto_aead *tfm)
+{
+	int cpu_index;
+	struct aead_instance *inst = aead_alg_instance(tfm);
+	struct pcrypt_instance_ctx *ictx = aead_instance_ctx(inst);
+	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(tfm);
+	struct crypto_aead *cipher;
+
+	cpu_index = (unsigned int)atomic_inc_return(&ictx->tfm_count) %
+		    cpumask_weight(cpu_online_mask);
+
+	ctx->cb_cpu = cpumask_nth(cpu_index, cpu_online_mask);
+	cipher = crypto_spawn_aead(&ictx->spawn);
+
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	ctx->child = cipher;
+	crypto_aead_set_reqsize(tfm, sizeof(struct pcrypt_request) +
+				     sizeof(struct aead_request) +
+				     crypto_aead_reqsize(cipher));
+
+	return 0;
+}
+
+static void pcrypt_aead_exit_tfm(struct crypto_aead *tfm)
+{
+	struct pcrypt_aead_ctx *ctx = crypto_aead_ctx(tfm);
+
+	crypto_free_aead(ctx->child);
+}
+
+static void pcrypt_free(struct aead_instance *inst)
+{
+	struct pcrypt_instance_ctx *ctx = aead_instance_ctx(inst);
+
+	crypto_drop_aead(&ctx->spawn);
+	padata_free_shell(ctx->psdec);
+	padata_free_shell(ctx->psenc);
+	kfree(inst);
+}
+
+static int pcrypt_init_instance(struct crypto_instance *inst,
+				struct crypto_alg *alg)
+{
+	if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
+		     "pcrypt(%s)", alg->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
+		return -ENAMETOOLONG;
+
+	memcpy(inst->alg.cra_name, alg->cra_name, CRYPTO_MAX_ALG_NAME);
+
+	inst->alg.cra_priority = alg->cra_priority + 100;
+	inst->alg.cra_blocksize = alg->cra_blocksize;
+	inst->alg.cra_alignmask = alg->cra_alignmask;
+
+	return 0;
+}
+
+static int pcrypt_create_aead(struct crypto_template *tmpl, struct rtattr **tb,
+			      struct crypto_attr_type *algt)
+{
+	struct pcrypt_instance_ctx *ctx;
+	struct aead_instance *inst;
+	struct aead_alg *alg;
+	u32 mask = crypto_algt_inherited_mask(algt);
+	int err;
+
+	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
+	if (!inst)
+		return -ENOMEM;
+
+	err = -ENOMEM;
+
+	ctx = aead_instance_ctx(inst);
+	ctx->psenc = padata_alloc_shell(pencrypt);
+	if (!ctx->psenc)
+		goto err_free_inst;
+
+	ctx->psdec = padata_alloc_shell(pdecrypt);
+	if (!ctx->psdec)
+		goto err_free_inst;
+
+	err = crypto_grab_aead(&ctx->spawn, aead_crypto_instance(inst),
+			       crypto_attr_alg_name(tb[1]), 0, mask);
+	if (err)
+		goto err_free_inst;
+
+	alg = crypto_spawn_aead_alg(&ctx->spawn);
+	err = pcrypt_init_instance(aead_crypto_instance(inst), &alg->base);
+	if (err)
+		goto err_free_inst;
+
+	inst->alg.base.cra_flags |= CRYPTO_ALG_ASYNC;
+
+	inst->alg.ivsize = crypto_aead_alg_ivsize(alg);
+	inst->alg.maxauthsize = crypto_aead_alg_maxauthsize(alg);
+
+	inst->alg.base.cra_ctxsize = sizeof(struct pcrypt_aead_ctx);
+
+	inst->alg.init = pcrypt_aead_init_tfm;
+	inst->alg.exit = pcrypt_aead_exit_tfm;
+
+	inst->alg.setkey = pcrypt_aead_setkey;
+	inst->alg.setauthsize = pcrypt_aead_setauthsize;
+	inst->alg.encrypt = pcrypt_aead_encrypt;
+	inst->alg.decrypt = pcrypt_aead_decrypt;
+
+	inst->free = pcrypt_free;
+
+	err = aead_register_instance(tmpl, inst);
+	if (err) {
+err_free_inst:
+		pcrypt_free(inst);
+	}
+	return err;
+}
+
+static int pcrypt_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct crypto_attr_type *algt;
+
+	algt = crypto_get_attr_type(tb);
+	if (IS_ERR(algt))
+		return PTR_ERR(algt);
+
+	switch (algt->type & algt->mask & CRYPTO_ALG_TYPE_MASK) {
+	case CRYPTO_ALG_TYPE_AEAD:
+		return pcrypt_create_aead(tmpl, tb, algt);
+	}
+
+	return -EINVAL;
+}
+
+static int pcrypt_sysfs_add(struct padata_instance *pinst, const char *name)
+{
+	int ret;
+
+	pinst->kobj.kset = pcrypt_kset;
+	ret = kobject_add(&pinst->kobj, NULL, "%s", name);
+	if (!ret)
+		kobject_uevent(&pinst->kobj, KOBJ_ADD);
+
+	return ret;
+}
+
+static int pcrypt_init_padata(struct padata_instance **pinst, const char *name)
+{
+	int ret = -ENOMEM;
+
+	*pinst = padata_alloc(name);
+	if (!*pinst)
+		return ret;
+
+	ret = pcrypt_sysfs_add(*pinst, name);
+	if (ret)
+		padata_free(*pinst);
+
+	return ret;
+}
+
+static struct crypto_template pcrypt_tmpl = {
+	.name = "pcrypt",
+	.create = pcrypt_create,
+	.module = THIS_MODULE,
+};
+
+static int __init pcrypt_init(void)
+{
+	int err = -ENOMEM;
+
+	pcrypt_kset = kset_create_and_add("pcrypt", NULL, kernel_kobj);
+	if (!pcrypt_kset)
+		goto err;
+
+	err = pcrypt_init_padata(&pencrypt, "pencrypt");
+	if (err)
+		goto err_unreg_kset;
+
+	err = pcrypt_init_padata(&pdecrypt, "pdecrypt");
+	if (err)
+		goto err_deinit_pencrypt;
+
+	return crypto_register_template(&pcrypt_tmpl);
+
+err_deinit_pencrypt:
+	padata_free(pencrypt);
+err_unreg_kset:
+	kset_unregister(pcrypt_kset);
+err:
+	return err;
+}
+
+static void __exit pcrypt_exit(void)
+{
+	crypto_unregister_template(&pcrypt_tmpl);
+
+	padata_free(pencrypt);
+	padata_free(pdecrypt);
+
+	kset_unregister(pcrypt_kset);
+}
+
+module_init(pcrypt_init);
+module_exit(pcrypt_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");
+MODULE_DESCRIPTION("Parallel crypto wrapper");
+MODULE_ALIAS_CRYPTO("pcrypt");