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, 88 insertions, 0 deletions

diff --git a/Documentation/crypto/libcrypto-hash.rst b/Documentation/crypto/libcrypto-hash.rst
new file mode 100644
index 000000000..fa4c54236
--- /dev/null
+++ b/Documentation/crypto/libcrypto-hash.rst
@@ -0,0 +1,88 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Hash functions, MACs, and XOFs
+==============================
+
+AES-CMAC and AES-XCBC-MAC
+-------------------------
+
+This API provides support for the AES-CMAC and AES-XCBC-MAC message
+authentication codes.
+
+.. kernel-doc:: include/crypto/aes-cbc-macs.h
+
+BLAKE2b
+-------
+
+This API provides support for the BLAKE2b cryptographic hash function.
+
+.. kernel-doc:: include/crypto/blake2b.h
+
+BLAKE2s
+-------
+
+This API provides support for the BLAKE2s cryptographic hash function.
+
+.. kernel-doc:: include/crypto/blake2s.h
+
+GHASH and POLYVAL
+-----------------
+
+This API provides support for the GHASH and POLYVAL universal hash functions.
+These algorithms are used only as internal components of other algorithms.
+
+.. kernel-doc:: include/crypto/gf128hash.h
+
+MD5
+---
+
+This API provides support for the MD5 cryptographic hash function and HMAC-MD5.
+This algorithm is obsolete and is supported only for backwards compatibility.
+
+.. kernel-doc:: include/crypto/md5.h
+
+NH
+--
+
+This API provides support for the NH universal hash function.  This algorithm is
+used only as an internal component of other algorithms.
+
+.. kernel-doc:: include/crypto/nh.h
+
+Poly1305
+--------
+
+This API provides support for the Poly1305 universal hash function.  This
+algorithm is used only as an internal component of other algorithms.
+
+.. kernel-doc:: include/crypto/poly1305.h
+
+SHA-1
+-----
+
+This API provides support for the SHA-1 cryptographic hash function and
+HMAC-SHA1.  This algorithm is obsolete and is supported only for backwards
+compatibility.
+
+.. kernel-doc:: include/crypto/sha1.h
+
+SHA-2
+-----
+
+This API provides support for the SHA-2 family of cryptographic hash functions,
+including SHA-224, SHA-256, SHA-384, and SHA-512.  This also includes their
+corresponding HMACs: HMAC-SHA224, HMAC-SHA256, HMAC-SHA384, and HMAC-SHA512.
+
+.. kernel-doc:: include/crypto/sha2.h
+
+SHA-3
+-----
+
+The SHA-3 API is documented in :ref:`sha3`.
+
+SM3
+---
+
+This API provides support for the SM3 cryptographic hash function.
+
+.. kernel-doc:: include/crypto/sm3.h