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Bug #21303
closed
heap-buffer-overflow of Array#difference via mutating hash method
Description
Hi, we found a heap-buffer-overflow of Array#difference via mutating hash
method. Here is the PoC.
class C
def hash
$a.clear
return 0
end
def eql?(other)
return true
end
end
$b = (1..20).to_a
$a = (1..10000).to_a
$a.push(C.new)
$a.difference($b, $b)
Specifically, calling Array#difference on an array with an object whose hash
method mutates the array causes memory corruption. Here, C#hash clears $a while
difference is iterating over it, breaking internal invariants and leading to a
crash or invalid memory access.
To reproduce, compile the recent Ruby with ASAN, and run the PoC.
$ ruby -v
ruby 3.0.2p107 (2021-07-07 revision 0db68f0233) [x86_64-linux-gnu]
$ ruby array_difference.rb
`RubyGems' were not loaded.
`error_highlight' was not loaded.
`did_you_mean' was not loaded.
`syntax_suggest' was not loaded.
=================================================================
==88761==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x51100001d500 at pc 0x598237a7f324 bp 0x7ffc9d9f0150 sp 0x7ffc9d9f0148
READ of size 8 at 0x51100001d500 thread T0
#0 0x598237a7f323 in RARRAY_AREF /media/test/ruby/build/../internal/array.h:147:11
#1 0x598237a7f323 in rb_ary_difference_multi /media/test/ruby/build/../array.c:5616:52
#2 0x598237a0ab3b in vm_call_cfunc_with_frame_ /media/test/ruby/build/../vm_insnhelper.c:3797:11
#3 0x5982379f34e3 in vm_call_method_each_type /media/test/ruby/build/../vm_insnhelper.c:4775:16
#4 0x5982379f2fd3 in vm_call_method /media/test/ruby/build/../vm_insnhelper.c
#5 0x5982379b91d8 in vm_sendish /media/test/ruby/build/../vm_insnhelper.c:5972:15
#6 0x5982379b91d8 in vm_exec_core /media/test/ruby/build/../insns.def:899:11
#7 0x5982379b1a47 in rb_vm_exec /media/test/ruby/build/../vm.c
#8 0x598237683ce0 in rb_ec_exec_node /media/test/ruby/build/../eval.c:281:9
#9 0x598237683ce0 in ruby_run_node /media/test/ruby/build/../eval.c:319:30
#10 0x59823767f3a0 in rb_main /media/test/ruby/build/../main.c:42:12
#11 0x59823767f3a0 in main /media/test/ruby/build/../main.c:62:12
#12 0x7f619c429d8f in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#13 0x7f619c429e3f in __libc_start_main csu/../csu/libc-start.c:392:3
#14 0x5982375a7d54 in _start (/media/test/ruby/build/ruby+0x148d54) (BuildId: 58c97094e0527fad484552e230da980d80ffa516)
Address 0x51100001d500 is a wild pointer inside of access range of size 0x000000000008.
SUMMARY: AddressSanitizer: heap-buffer-overflow /media/test/ruby/build/../internal/array.h:147:11 in RARRAY_AREF
Shadow bytes around the buggy address:
0x51100001d280: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d300: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d380: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d400: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d480: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x51100001d500:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d580: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d600: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d680: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d700: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x51100001d780: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==88761==ABORTING
../triaged/array_difference.rb:16: [BUG] ASAN error
ruby 3.5.0dev (2025-05-02T21:28:25Z master 36c64b3be8) +PRISM [x86_64-linux]
-- Control frame information -----------------------------------------------
c:0003 p:---- s:0012 e:000011 CFUNC :difference
c:0002 p:0048 s:0006 e:000005 EVAL ../triaged/array_difference.rb:16 [FINISH]
c:0001 p:0000 s:0003 E:000540 DUMMY [FINISH]
-- Ruby level backtrace information ----------------------------------------
../triaged/array_difference.rb:16:in '<main>'
../triaged/array_difference.rb:16:in 'difference'
-- Threading information ---------------------------------------------------
Total ractor count: 1
Ruby thread count for this ractor: 1
-- C level backtrace information -------------------------------------------
./ruby(___interceptor_backtrace) [0x5982375ec006]
/media/test/ruby/build/ruby(rb_print_backtrace+0x14) [0x598237d3a337] /media/test/ruby/build/../vm_dump.c:839
/media/test/ruby/build/ruby(rb_vm_bugreport) /media/test/ruby/build/../vm_dump.c:1171
/media/test/ruby/build/ruby(rb_bug_without_die_internal+0x23c) [0x598237c8e76c] /media/test/ruby/build/../error.c:1097
/media/test/ruby/build/ruby(rb_bug_without_die+0x127) [0x598237c8e487] /media/test/ruby/build/../error.c:1106
./ruby(0x598237665bc6) [0x598237665bc6]
./ruby(0x598237646c9f) [0x598237646c9f]
./ruby(0x598237649ce5) [0x598237649ce5]
./ruby(__asan_report_load8) [0x59823764a988]
/media/test/ruby/build/ruby(rb_ary_difference_multi+0xb64) [0x598237a7f324] ../internal/array.h:147
/media/test/ruby/build/ruby(vm_cfp_consistent_p+0x0) [0x598237a0ab3c] ../vm_insnhelper.c:3797
/media/test/ruby/build/ruby(vm_call_cfunc_with_frame_) ../vm_insnhelper.c:3799
/media/test/ruby/build/ruby(vm_call_method_each_type+0x264) [0x5982379f34e4] ../vm_insnhelper.c:4775
./ruby(vm_call_method+0x2d4) [0x5982379f2fd4]
/media/test/ruby/build/ruby(vm_sendish+0x1c8) [0x5982379b91d9] ../vm_insnhelper.c:5972
/media/test/ruby/build/ruby(vm_exec_core) ../insns.def:899
./ruby(vm_exec_loop+0x0) [0x5982379b1a48]
/media/test/ruby/build/ruby(rb_vm_exec) /media/test/ruby/build/../vm.c:2621
/media/test/ruby/build/ruby(rb_ec_exec_node+0x53) [0x598237683ce1] /media/test/ruby/build/../eval.c:281
/media/test/ruby/build/ruby(ruby_run_node) /media/test/ruby/build/../eval.c:319
/media/test/ruby/build/ruby(rb_main+0x29) [0x59823767f3a1] /media/test/ruby/build/../main.c:42
/media/test/ruby/build/ruby(main) /media/test/ruby/build/../main.c:62
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_call_main+0x80) [0x7f619c429d90] ../sysdeps/nptl/libc_start_call_main.h:58
/lib/x86_64-linux-gnu/libc.so.6(call_init+0x0) [0x7f619c429e40] ../csu/libc-start.c:392
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main_impl) ../csu/libc-start.c:379
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main) (null):0
./ruby(_start) [0x5982375a7d55]
-- Other runtime information -----------------------------------------------
* Loaded script: ../triaged/array_difference.rb
* Loaded features:
0 enumerator.so
1 thread.rb
2 fiber.so
3 rational.so
4 complex.so
5 ruby2_keywords.rb
6 set.rb
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