Bug #20915
Updated by viralpraxis (Iaroslav Kurbatov) 23 days ago
I'm getting a segfault in the following example
```ruby
C = Class.new do
alias_method :new_to_s, :to_s
end
TracePoint.new(:c_call, &:parameters).enable { C.new.new_to_s }
```
Proposed fix: https://github.com/ruby/ruby/pull/12186
Ruby: `MRI 3.3.6`, also `ruby 3.4.0dev (2024-11-27T19:36:50Z master 7dd2afbe3a) +PRISM [x86_64-linux]`
The root cause of the issue lies in the `rb_tracearg_parameters` function within the `RUBY_EVENT_C_RETURN` branch.
Specifically, when the invoked method is an alias for a C function, `rb_method_entry_without_refinements(..., trace_arg->called_id, ...)` may return NULL.
In that case we can fallback to `trace_arg->id`.
Some additional context: before https://github.com/ruby/ruby/commit/837ef8911c638c3e2bdb6af710de7c1fac7b5f90 this code path used single `trace_arg->id` lookup, and the commit changed it to `trace_arg->called_id`. So we have to make both lookups to handle all edge cases.
Output:
```
[BUG] Segmentation fault at 0x0000000000000010
ruby 3.4.0dev (2024-11-27T19:36:50Z master 7dd2afbe3a) +PRISM [x86_64-linux]
-- Control frame information -----------------------------------------------
c:0005 p:0003 s:0022 e:000021 METHOD <internal:trace_point>:333 [FINISH]
c:0004 p:0006 s:0018 e:000016 BLOCK test.rb:5 [FINISH]
c:0003 p:0003 s:0014 e:000013 METHOD <internal:trace_point>:265
c:0002 p:0021 s:0006 e:000005 EVAL test.rb:5 [FINISH]
c:0001 p:0000 s:0003 E:001470 DUMMY [FINISH]
-- Ruby level backtrace information ----------------------------------------
test.rb:5:in '<main>'
<internal:trace_point>:265:in 'enable'
test.rb:5:in 'block in <main>'
<internal:trace_point>:333:in 'parameters'
-- Threading information ---------------------------------------------------
Total ractor count: 1
Ruby thread count for this ractor: 1
-- Machine register context ------------------------------------------------
RIP: 0x0000609a79ce6f16 RBP: 0x00007ffd98dc9030 RSP: 0x00007ffd98dc9020
RAX: 0x0000000000000000 RBX: 0x0000609a7b40bdf0 RCX: 0x000000000000b6d1
RDX: 0x0000000000000000 RDI: 0x0000000000000000 RSI: 0x0000000000000b6d
R8: 0x0000000000000000 R9: 0x000076e90ee24aa0 R10: 0x0000000000000001
R11: 0x0000000000000010 R12: 0x0000000000000002 R13: 0x0000000000000000
R14: 0x0000609a7b40be08 R15: 0x000076e90effeef8 EFL: 0x0000000000010202
-- C level backtrace information -------------------------------------------
./ruby(0x609a79e219f7) [0x609a79e219f7]
./ruby(0x609a79e2214b) [0x609a79e2214b]
./ruby(0x609a7a02e998) [0x609a7a02e998]
./ruby(0x609a79d61811) [0x609a79d61811]
/lib/x86_64-linux-gnu/libc.so.6(0x76e90f845320) [0x76e90f845320]
./ruby(0x609a79ce6f16) [0x609a79ce6f16]
./ruby(rb_tracearg_parameters+0x1a1) [0x609a79e25db2] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:943
./ruby(tracepoint_attr_parameters+0x21) [0x609a79e26252] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:1121
./ruby(0x609a79df8f0b) [0x609a79df8f0b]
./ruby(0x609a79df9904) [0x609a79df9904]
./ruby(0x609a79df9983) [0x609a79df9983]
./ruby(0x609a79e0147e) [0x609a79e0147e]
./ruby(0x609a79e15d9c) [0x609a79e15d9c]
./ruby(0x609a79e09991) [0x609a79e09991]
./ruby(0x609a79e091bd) [0x609a79e091bd]
./ruby(0x609a79e0ad1f) [0x609a79e0ad1f]
./ruby(0x609a79e0ba2b) [0x609a79e0ba2b]
./ruby(rb_funcall_with_block_kw) [0x609a79e0c7ef]
./ruby(0x609a79d8d877) [0x609a79d8d877]
./ruby(0x609a79df3832) [0x609a79df3832]
./ruby(0x609a79e13238) [0x609a79e13238]
./ruby(0x609a79e13888) [0x609a79e13888]
./ruby(rb_proc_call_with_block_kw) [0x609a79ce3b6a]
./ruby(rb_proc_call_with_block) [0x609a79ce3bcf]
./ruby(tp_call_trace+0x8d) [0x609a79e2641c] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:1188
./ruby(exec_hooks_body+0x114) [0x609a79e245d7] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:354
./ruby(exec_hooks_protected+0x166) [0x609a79e24838] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:401
./ruby(rb_exec_event_hooks+0x12d) [0x609a79e249e2] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:446
./ruby(0x609a79ddbefe) [0x609a79ddbefe]
./ruby(0x609a79deef34) [0x609a79deef34]
./ruby(0x609a79def260) [0x609a79def260]
./ruby(0x609a79def38d) [0x609a79def38d]
./ruby(0x609a79def7d4) [0x609a79def7d4]
./ruby(0x609a79df243b) [0x609a79df243b]
./ruby(0x609a79df0646) [0x609a79df0646]
./ruby(0x609a79df2c0d) [0x609a79df2c0d]
./ruby(0x609a79df2ee7) [0x609a79df2ee7]
./ruby(0x609a79df30e9) [0x609a79df30e9]
./ruby(0x609a79df580a) [0x609a79df580a]
./ruby(0x609a79dfd8dd) [0x609a79dfd8dd]
./ruby(0x609a79e15d9c) [0x609a79e15d9c]
./ruby(0x609a79e12a8c) [0x609a79e12a8c]
./ruby(0x609a79e12c48) [0x609a79e12c48]
./ruby(0x609a79e12c86) [0x609a79e12c86]
./ruby(0x609a79e0cc8c) [0x609a79e0cc8c]
./ruby(rb_yield) [0x609a79e0cce0]
./ruby(rb_ensure) [0x609a79c20ea4]
./ruby(tracepoint_enable_m+0x1a5) [0x609a79e26c05] /home/viralpraxis/Documents/open_source/ruby/vm_trace.c:1414
./ruby(0x609a79df8fd7) [0x609a79df8fd7]
./ruby(0x609a79df9904) [0x609a79df9904]
./ruby(0x609a79df99d1) [0x609a79df99d1]
./ruby(0x609a79e01583) [0x609a79e01583]
./ruby(0x609a79e15d9c) [0x609a79e15d9c]
./ruby(rb_iseq_eval_main) [0x609a79e16bcb]
./ruby(0x609a79c1f112) [0x609a79c1f112]
./ruby(ruby_run_node) [0x609a79c1f283]
./ruby(0x609a79c1aae4) [0x609a79c1aae4]
./ruby(0x609a79c1ab45) [0x609a79c1ab45]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_call_main+0x7a) [0x76e90f82a1ca] ../sysdeps/nptl/libc_start_call_main.h:58
/lib/x86_64-linux-gnu/libc.so.6(call_init+0x0) [0x76e90f82a28b] ../csu/libc-start.c:360
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main_impl) ../csu/libc-start.c:347
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main) (null):0
[0x609a79c1a9c5]
-- Other runtime information -----------------------------------------------
* Loaded script: test.rb
* Loaded features:
0 enumerator.so
1 thread.rb
2 fiber.so
3 rational.so
4 complex.so
5 ruby2_keywords.rb
```