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, 245 insertions, 0 deletions

diff --git a/include/crypto/internal/kpp.h b/include/crypto/internal/kpp.h
new file mode 100644
index 000000000..0a6db8c4a
--- /dev/null
+++ b/include/crypto/internal/kpp.h
@@ -0,0 +1,245 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Key-agreement Protocol Primitives (KPP)
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ */
+#ifndef _CRYPTO_KPP_INT_H
+#define _CRYPTO_KPP_INT_H
+#include <crypto/kpp.h>
+#include <crypto/algapi.h>
+
+/**
+ * struct kpp_instance - KPP template instance
+ * @free: Callback getting invoked upon instance destruction. Must be set.
+ * @s: Internal. Generic crypto core instance state properly layout
+ *     to alias with @alg as needed.
+ * @alg: The &struct kpp_alg implementation provided by the instance.
+ */
+struct kpp_instance {
+	void (*free)(struct kpp_instance *inst);
+	union {
+		struct {
+			char head[offsetof(struct kpp_alg, base)];
+			struct crypto_instance base;
+		} s;
+		struct kpp_alg alg;
+	};
+};
+
+/**
+ * struct crypto_kpp_spawn - KPP algorithm spawn
+ * @base: Internal. Generic crypto core spawn state.
+ *
+ * Template instances can get a hold on some inner KPP algorithm by
+ * binding a &struct crypto_kpp_spawn via
+ * crypto_grab_kpp(). Transforms may subsequently get instantiated
+ * from the referenced inner &struct kpp_alg by means of
+ * crypto_spawn_kpp().
+ */
+struct crypto_kpp_spawn {
+	struct crypto_spawn base;
+};
+
+/*
+ * Transform internal helpers.
+ */
+static inline void *kpp_request_ctx(struct kpp_request *req)
+{
+	return req->__ctx;
+}
+
+static inline void *kpp_request_ctx_dma(struct kpp_request *req)
+{
+	unsigned int align = crypto_dma_align();
+
+	if (align <= crypto_tfm_ctx_alignment())
+		align = 1;
+
+	return PTR_ALIGN(kpp_request_ctx(req), align);
+}
+
+static inline void kpp_set_reqsize(struct crypto_kpp *kpp,
+				   unsigned int reqsize)
+{
+	kpp->reqsize = reqsize;
+}
+
+static inline void kpp_set_reqsize_dma(struct crypto_kpp *kpp,
+				       unsigned int reqsize)
+{
+	reqsize += crypto_dma_align() & ~(crypto_tfm_ctx_alignment() - 1);
+	kpp->reqsize = reqsize;
+}
+
+static inline void *kpp_tfm_ctx(struct crypto_kpp *tfm)
+{
+	return crypto_tfm_ctx(&tfm->base);
+}
+
+static inline void *kpp_tfm_ctx_dma(struct crypto_kpp *tfm)
+{
+	return crypto_tfm_ctx_dma(&tfm->base);
+}
+
+static inline void kpp_request_complete(struct kpp_request *req, int err)
+{
+	crypto_request_complete(&req->base, err);
+}
+
+static inline const char *kpp_alg_name(struct crypto_kpp *tfm)
+{
+	return crypto_kpp_tfm(tfm)->__crt_alg->cra_name;
+}
+
+/*
+ * Template instance internal helpers.
+ */
+/**
+ * kpp_crypto_instance() - Cast a &struct kpp_instance to the corresponding
+ *                         generic &struct crypto_instance.
+ * @inst: Pointer to the &struct kpp_instance to be cast.
+ * Return: A pointer to the &struct crypto_instance embedded in @inst.
+ */
+static inline struct crypto_instance *kpp_crypto_instance(
+	struct kpp_instance *inst)
+{
+	return &inst->s.base;
+}
+
+/**
+ * kpp_instance() - Cast a generic &struct crypto_instance to the corresponding
+ *                  &struct kpp_instance.
+ * @inst: Pointer to the &struct crypto_instance to be cast.
+ * Return: A pointer to the &struct kpp_instance @inst is embedded in.
+ */
+static inline struct kpp_instance *kpp_instance(struct crypto_instance *inst)
+{
+	return container_of(inst, struct kpp_instance, s.base);
+}
+
+/**
+ * kpp_alg_instance() - Get the &struct kpp_instance a given KPP transform has
+ *                      been instantiated from.
+ * @kpp: The KPP transform instantiated from some &struct kpp_instance.
+ * Return: The &struct kpp_instance associated with @kpp.
+ */
+static inline struct kpp_instance *kpp_alg_instance(struct crypto_kpp *kpp)
+{
+	return kpp_instance(crypto_tfm_alg_instance(&kpp->base));
+}
+
+/**
+ * kpp_instance_ctx() - Get a pointer to a &struct kpp_instance's implementation
+ *                      specific context data.
+ * @inst: The &struct kpp_instance whose context data to access.
+ *
+ * A KPP template implementation may allocate extra memory beyond the
+ * end of a &struct kpp_instance instantiated from &crypto_template.create().
+ * This function provides a means to obtain a pointer to this area.
+ *
+ * Return: A pointer to the implementation specific context data.
+ */
+static inline void *kpp_instance_ctx(struct kpp_instance *inst)
+{
+	return crypto_instance_ctx(kpp_crypto_instance(inst));
+}
+
+/*
+ * KPP algorithm (un)registration functions.
+ */
+/**
+ * crypto_register_kpp() -- Register key-agreement protocol primitives algorithm
+ *
+ * Function registers an implementation of a key-agreement protocol primitive
+ * algorithm
+ *
+ * @alg:	algorithm definition
+ *
+ * Return: zero on success; error code in case of error
+ */
+int crypto_register_kpp(struct kpp_alg *alg);
+
+/**
+ * crypto_unregister_kpp() -- Unregister key-agreement protocol primitive
+ * algorithm
+ *
+ * Function unregisters an implementation of a key-agreement protocol primitive
+ * algorithm
+ *
+ * @alg:	algorithm definition
+ */
+void crypto_unregister_kpp(struct kpp_alg *alg);
+
+/**
+ * kpp_register_instance() - Register a KPP template instance.
+ * @tmpl: The instantiating template.
+ * @inst: The KPP template instance to be registered.
+ * Return: %0 on success, negative error code otherwise.
+ */
+int kpp_register_instance(struct crypto_template *tmpl,
+			  struct kpp_instance *inst);
+
+/*
+ * KPP spawn related functions.
+ */
+/**
+ * crypto_grab_kpp() - Look up a KPP algorithm and bind a spawn to it.
+ * @spawn: The KPP spawn to bind.
+ * @inst: The template instance owning @spawn.
+ * @name: The KPP algorithm name to look up.
+ * @type: The type bitset to pass on to the lookup.
+ * @mask: The mask bismask to pass on to the lookup.
+ * Return: %0 on success, a negative error code otherwise.
+ */
+int crypto_grab_kpp(struct crypto_kpp_spawn *spawn,
+		    struct crypto_instance *inst,
+		    const char *name, u32 type, u32 mask);
+
+/**
+ * crypto_drop_kpp() - Release a spawn previously bound via crypto_grab_kpp().
+ * @spawn: The spawn to release.
+ */
+static inline void crypto_drop_kpp(struct crypto_kpp_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+/**
+ * crypto_spawn_kpp_alg() - Get the algorithm a KPP spawn has been bound to.
+ * @spawn: The spawn to get the referenced &struct kpp_alg for.
+ *
+ * This function as well as the returned result are safe to use only
+ * after @spawn has been successfully bound via crypto_grab_kpp() and
+ * up to until the template instance owning @spawn has either been
+ * registered successfully or the spawn has been released again via
+ * crypto_drop_spawn().
+ *
+ * Return: A pointer to the &struct kpp_alg referenced from the spawn.
+ */
+static inline struct kpp_alg *crypto_spawn_kpp_alg(
+	struct crypto_kpp_spawn *spawn)
+{
+	return container_of(spawn->base.alg, struct kpp_alg, base);
+}
+
+/**
+ * crypto_spawn_kpp() - Create a transform from a KPP spawn.
+ * @spawn: The spawn previously bound to some &struct kpp_alg via
+ *         crypto_grab_kpp().
+ *
+ * Once a &struct crypto_kpp_spawn has been successfully bound to a
+ * &struct kpp_alg via crypto_grab_kpp(), transforms for the latter
+ * may get instantiated from the former by means of this function.
+ *
+ * Return: A pointer to the freshly created KPP transform on success
+ * or an ``ERR_PTR()`` otherwise.
+ */
+static inline struct crypto_kpp *crypto_spawn_kpp(
+	struct crypto_kpp_spawn *spawn)
+{
+	return crypto_spawn_tfm2(&spawn->base);
+}
+
+#endif