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, 89 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
new file mode 100644
index 000000000..d5e596606
--- /dev/null
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Platform Security Processor (PSP) interface driver
+ *
+ * Copyright (C) 2017-2019 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ */
+
+#ifndef __SEV_DEV_H__
+#define __SEV_DEV_H__
+
+#include <linux/device.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/wait.h>
+#include <linux/dmapool.h>
+#include <linux/hw_random.h>
+#include <linux/bitops.h>
+#include <linux/interrupt.h>
+#include <linux/irqreturn.h>
+#include <linux/dmaengine.h>
+#include <linux/psp-sev.h>
+#include <linux/miscdevice.h>
+#include <linux/capability.h>
+
+#define SEV_CMDRESP_CMD			GENMASK(26, 16)
+#define SEV_CMD_COMPLETE		BIT(1)
+#define SEV_CMDRESP_IOC			BIT(0)
+
+struct sev_misc_dev {
+	struct kref refcount;
+	struct miscdevice misc;
+};
+
+struct sev_tio_status;
+
+struct sev_device {
+	struct device *dev;
+	struct psp_device *psp;
+
+	void __iomem *io_regs;
+
+	struct sev_vdata *vdata;
+
+	unsigned int int_rcvd;
+	wait_queue_head_t int_queue;
+	struct sev_misc_dev *misc;
+
+	u8 api_major;
+	u8 api_minor;
+	u8 build;
+
+	void *cmd_buf;
+	void *cmd_buf_backup;
+	bool cmd_buf_active;
+	bool cmd_buf_backup_active;
+
+	bool snp_initialized;
+
+	struct kobject *sev_kobj;
+	struct kobject *verify_mit;
+
+	struct sev_user_data_status sev_plat_status;
+
+	struct sev_user_data_snp_status snp_plat_status;
+	struct snp_feature_info snp_feat_info_0;
+
+	struct tsm_dev *tsmdev;
+	struct sev_tio_status *tio_status;
+};
+
+int sev_dev_init(struct psp_device *psp);
+void sev_dev_destroy(struct psp_device *psp);
+
+int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret);
+
+void sev_pci_init(void);
+void sev_pci_exit(void);
+
+struct page *snp_alloc_hv_fixed_pages(unsigned int num_2mb_pages);
+void snp_free_hv_fixed_pages(struct page *page);
+
+void sev_tsm_init_locked(struct sev_device *sev, void *tio_status_page);
+void sev_tsm_uninit(struct sev_device *sev);
+int sev_tio_cmd_buffer_len(int cmd);
+
+#endif /* __SEV_DEV_H */