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, 39 insertions, 0 deletions

diff --git a/Documentation/input/shape.svg b/Documentation/input/shape.svg
new file mode 100644
index 000000000..fc0af44db
--- /dev/null
+++ b/Documentation/input/shape.svg
@@ -0,0 +1,39 @@
+<svg width="7.95in" height="3.70in" version="1.1" viewBox="1956 1041 9354.492 4306.001" xmlns="http://www.w3.org/2000/svg">
+ <polyline transform="translate(-121.88 -68.4)" points="4200 3600 4200 3075 4950 2325 7425 2325 8250 3150 8250 3600" fill="none" stroke="#000" stroke-width="15"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4200 3675 4200 5400" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="8250 3675 8250 5400" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="3675 3600 8700 3600" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="8775 3600 10200 3600" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="8325 3150 9075 3150" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="7500 2325 10200 2325" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="3600 3600 3e3 3600" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4125 3075 3e3 3075" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4217 5400 8158 5400" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="8053 5430 8173 5400 8053 5370" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4322 5370 4202 5400 4322 5430" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="10125 2342 10125 3583" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="10095 3478 10125 3598 10155 3478" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="10155 2447 10125 2327 10095 2447" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="3e3 3167 3e3 3583" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="2970 3478 3e3 3598 3030 3478" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="3030 3272 3e3 3152 2970 3272" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="9075 3167 9075 3583" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="9045 3478 9075 3598 9105 3478" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="9105 3272 9075 3152 9045 3272" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4950 2325 4950 1200" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="7425 2325 7425 1200" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4200 3075 4200 2400 3600 1800 3600 1200" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="8250 3150 8250 2475 8775 1950 8775 1200" fill="none" stroke="#000" stroke-dasharray="40, 40" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="3617 1275 4933 1275" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="4828 1305 4948 1275 4828 1245" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="3722 1245 3602 1275 3722 1305" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="7442 1275 8683 1275" fill="none" stroke="#000" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="8578 1305 8698 1275 8578 1245" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <polyline transform="translate(-121.88 -68.4)" points="7547 1245 7427 1275 7547 1305" fill="none" stroke="#000" stroke-miterlimit="8" stroke-width="7"/>
+ <text x="5953.125" y="5256.6001" fill="#000000" font-family="sans-serif" font-size="144px" stroke-width=".025in" text-anchor="middle" xml:space="preserve">Effect duration</text>
+ <text x="10078.125" y="2931.5999" fill="#000000" font-family="sans-serif" font-size="144px" stroke-width=".025in" xml:space="preserve">Effect magnitude</text>
+ <text x="9028.125" y="3381.5999" fill="#000000" font-family="sans-serif" font-size="144px" stroke-width=".025in" xml:space="preserve">Fade level</text>
+ <text x="4153.125" y="1131.6" fill="#000000" font-family="sans-serif" font-size="144px" stroke-width=".025in" text-anchor="middle" xml:space="preserve">Attack length</text>
+ <text x="8053.125" y="1131.6" fill="#000000" font-family="sans-serif" font-size="144px" stroke-width=".025in" text-anchor="middle" xml:space="preserve">Fade length</text>
+ <text x="2803.125" y="3306.5999" fill="#000000" font-family="sans-serif" font-size="144px" stroke-width=".025in" text-anchor="end" xml:space="preserve">Attack level</text>
+</svg>