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, 73 insertions, 0 deletions

diff --git a/fs/smb/server/Kconfig b/fs/smb/server/Kconfig
new file mode 100644
index 000000000..221ec9717
--- /dev/null
+++ b/fs/smb/server/Kconfig
@@ -0,0 +1,73 @@
+config SMB_SERVER
+	tristate "SMB3 server support"
+	depends on INET
+	depends on MULTIUSER
+	depends on FILE_LOCKING
+	select NLS
+	select NLS_UTF8
+	select NLS_UCS2_UTILS
+	select CRYPTO
+	select CRYPTO_LIB_AES_CBC_MACS
+	select CRYPTO_LIB_ARC4
+	select CRYPTO_LIB_MD5
+	select CRYPTO_LIB_SHA256
+	select CRYPTO_LIB_SHA512
+	select CRYPTO_LIB_UTILS
+	select CRYPTO_AEAD2
+	select CRYPTO_CCM
+	select CRYPTO_GCM
+	select ASN1
+	select OID_REGISTRY
+	select CRC32
+	default n
+	help
+	  Choose Y here if you want to allow SMB3 compliant clients
+	  to access files residing on this system using SMB3 protocol.
+	  To compile the SMB3 server support as a module,
+	  choose M here: the module will be called ksmbd.
+
+	  You may choose to use a samba server instead, in which
+	  case you can choose N here.
+
+	  You also need to install user space programs which can be found
+	  in ksmbd-tools, available from
+	  https://github.com/cifsd-team/ksmbd-tools.
+	  More detail about how to run the ksmbd kernel server is
+	  available via the README file
+	  (https://github.com/cifsd-team/ksmbd-tools/blob/master/README).
+
+	  ksmbd kernel server includes support for auto-negotiation,
+	  Secure negotiate, Pre-authentication integrity, oplock/lease,
+	  compound requests, multi-credit, packet signing, RDMA(smbdirect),
+	  smb3 encryption, copy-offload, secure per-user session
+	  establishment via Kerberos or NTLMv2.
+
+if SMB_SERVER
+
+config SMB_SERVER_SMBDIRECT
+	bool "Support for SMB Direct protocol"
+	depends on SMB_SERVER && INFINIBAND && INFINIBAND_ADDR_TRANS
+	depends on SMB_SERVER=m || INFINIBAND=y
+	select SMBDIRECT
+	default n
+
+	help
+	  Enables SMB Direct support for SMB 3.0, 3.02 and 3.1.1.
+
+	  SMB Direct allows transferring SMB packets over RDMA. If unsure,
+	  say N.
+
+endif
+
+config SMB_SERVER_CHECK_CAP_NET_ADMIN
+	bool "Enable check network administration capability"
+	depends on SMB_SERVER
+	default y
+
+	help
+	  Prevent unprivileged processes to start the ksmbd kernel server.
+
+config SMB_SERVER_KERBEROS5
+	bool "Support for Kerberos 5"
+	depends on SMB_SERVER
+	default y