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, 123 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/sev-dev-tio.h b/drivers/crypto/ccp/sev-dev-tio.h
new file mode 100644
index 000000000..67512b3db
--- /dev/null
+++ b/drivers/crypto/ccp/sev-dev-tio.h
@@ -0,0 +1,123 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __PSP_SEV_TIO_H__
+#define __PSP_SEV_TIO_H__
+
+#include <linux/pci-tsm.h>
+#include <linux/pci-ide.h>
+#include <linux/tsm.h>
+#include <uapi/linux/psp-sev.h>
+
+struct sla_addr_t {
+	union {
+		u64 sla;
+		struct {
+			u64 page_type	:1,
+			    page_size	:1,
+			    reserved1	:10,
+			    pfn		:40,
+			    reserved2	:12;
+		};
+	};
+} __packed;
+
+#define SEV_TIO_MAX_COMMAND_LENGTH	128
+
+/* SPDM control structure for DOE */
+struct tsm_spdm {
+	unsigned long req_len;
+	void *req;
+	unsigned long rsp_len;
+	void *rsp;
+};
+
+/* Describes TIO device */
+struct tsm_dsm_tio {
+	u8 cert_slot;
+	struct sla_addr_t dev_ctx;
+	struct sla_addr_t req;
+	struct sla_addr_t resp;
+	struct sla_addr_t scratch;
+	struct sla_addr_t output;
+	size_t output_len;
+	size_t scratch_len;
+	struct tsm_spdm spdm;
+	struct sla_buffer_hdr *reqbuf; /* vmap'ed @req for DOE */
+	struct sla_buffer_hdr *respbuf; /* vmap'ed @resp for DOE */
+
+	int cmd;
+	int psp_ret;
+	u8 cmd_data[SEV_TIO_MAX_COMMAND_LENGTH];
+	void *data_pg; /* Data page for DEV_STATUS/TDI_STATUS/TDI_INFO/ASID_FENCE */
+
+#define TIO_IDE_MAX_TC	8
+	struct pci_ide *ide[TIO_IDE_MAX_TC];
+};
+
+/* Describes TSM structure for PF0 pointed by pci_dev->tsm */
+struct tio_dsm {
+	struct pci_tsm_pf0 tsm;
+	struct tsm_dsm_tio data;
+	struct sev_device *sev;
+};
+
+/* Data object IDs */
+#define SPDM_DOBJ_ID_NONE		0
+#define SPDM_DOBJ_ID_REQ		1
+#define SPDM_DOBJ_ID_RESP		2
+
+struct spdm_dobj_hdr {
+	u32 id;     /* Data object type identifier */
+	u32 length; /* Length of the data object, INCLUDING THIS HEADER */
+	struct { /* Version of the data object structure */
+		u8 minor;
+		u8 major;
+	} version;
+} __packed;
+
+/**
+ * struct sev_tio_status - TIO_STATUS command's info_paddr buffer
+ *
+ * @length: Length of this structure in bytes
+ * @tio_en: Indicates that SNP_INIT_EX initialized the RMP for SEV-TIO
+ * @tio_init_done: Indicates TIO_INIT has been invoked
+ * @spdm_req_size_min: Minimum SPDM request buffer size in bytes
+ * @spdm_req_size_max: Maximum SPDM request buffer size in bytes
+ * @spdm_scratch_size_min: Minimum SPDM scratch buffer size in bytes
+ * @spdm_scratch_size_max: Maximum SPDM scratch buffer size in bytes
+ * @spdm_out_size_min: Minimum SPDM output buffer size in bytes
+ * @spdm_out_size_max: Maximum for the SPDM output buffer size in bytes
+ * @spdm_rsp_size_min: Minimum SPDM response buffer size in bytes
+ * @spdm_rsp_size_max: Maximum SPDM response buffer size in bytes
+ * @devctx_size: Size of a device context buffer in bytes
+ * @tdictx_size: Size of a TDI context buffer in bytes
+ * @tio_crypto_alg: TIO crypto algorithms supported
+ */
+struct sev_tio_status {
+	u32 length;
+	u32 tio_en	  :1,
+	    tio_init_done :1,
+	    reserved	  :30;
+	u32 spdm_req_size_min;
+	u32 spdm_req_size_max;
+	u32 spdm_scratch_size_min;
+	u32 spdm_scratch_size_max;
+	u32 spdm_out_size_min;
+	u32 spdm_out_size_max;
+	u32 spdm_rsp_size_min;
+	u32 spdm_rsp_size_max;
+	u32 devctx_size;
+	u32 tdictx_size;
+	u32 tio_crypto_alg;
+	u8 reserved2[12];
+} __packed;
+
+int sev_tio_init_locked(void *tio_status_page);
+int sev_tio_continue(struct tsm_dsm_tio *dev_data);
+
+int sev_tio_dev_create(struct tsm_dsm_tio *dev_data, u16 device_id, u16 root_port_id,
+		       u8 segment_id);
+int sev_tio_dev_connect(struct tsm_dsm_tio *dev_data, u8 tc_mask, u8 ids[8], u8 cert_slot);
+int sev_tio_dev_disconnect(struct tsm_dsm_tio *dev_data, bool force);
+int sev_tio_dev_reclaim(struct tsm_dsm_tio *dev_data);
+
+#endif	/* __PSP_SEV_TIO_H__ */