ruby-core

Issue #19575 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 3.0: REQUIRED, 3.1: REQUIRED, 3.2: REQUIRED to 3.0: REQUIRED, 3.1: REQUIRED, 3.2: DONE

ruby_3_2 cb8d656100659eaee44042ca680886c30892df04 merged revision(s) a84c99468f26a9f79fec57926d561ed906505eac.

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Bug #19575: Crash in Time on 32-bit systems
https://bugs.ruby-lang.org/issues/19575#change-103891

* Author: peterzhu2118 (Peter Zhu)
* Status: Closed
* Priority: Normal
* Backport: 3.0: REQUIRED, 3.1: REQUIRED, 3.2: DONE
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GitHub PR: https://github.com/ruby/ruby/pull/7650

struct vtm is packed causing it to have a size that is not aligned on 32-bit systems. When allocating it on the stack, it will have unaligned addresses which means that the fields won't be marked by the GC when scanning the stack (since the GC only marks aligned addresses). This can cause crashes when the fields are heap allocated objects like Bignums.

The proposed fix moves the flags in struct time_object into struct vtm for space efficiency and removes the need for packing.

This is an example of a crash:

    ruby(rb_print_backtrace+0xd) [0x56848945] ../src/vm_dump.c:785
    ruby(rb_vm_bugreport) ../src/vm_dump.c:1101
    ruby(rb_assert_failure+0x7a) [0x56671857] ../src/error.c:878
    ruby(vm_search_cc+0x0) [0x56666e47] ../src/vm_method.c:1366
    ruby(rb_vm_search_method_slowpath) ../src/vm_insnhelper.c:2090
    ruby(callable_method_entry+0x5) [0x568232d3] ../src/vm_method.c:1406
    ruby(rb_callable_method_entry) ../src/vm_method.c:1413
    ruby(gccct_method_search_slowpath) ../src/vm_eval.c:427
    ruby(gccct_method_search+0x20f) [0x568237ef] ../src/vm_eval.c:476
    ruby(opt_equality_by_mid_slowpath+0x2c) [0x5682388c] ../src/vm_insnhelper.c:2338
    ruby(rb_equal+0x37) [0x566fe577] ../src/object.c:133
    ruby(rb_big_eq+0x34) [0x56876ee4] ../src/bignum.c:5554
    ruby(rb_int_equal+0x14) [0x566f3ed4] ../src/numeric.c:4640
    ruby(rb_int_equal) ../src/numeric.c:4634
    ruby(vm_call0_cfunc_with_frame+0x6d) [0x568303c2] ../src/vm_eval.c:148
    ruby(vm_call0_cfunc) ../src/vm_eval.c:162
    ruby(vm_call0_body) ../src/vm_eval.c:208
    ruby(rb_funcallv_scope+0xd1) [0x56833971] ../src/vm_eval.c:85
    ruby(RB_TEST+0x0) [0x567e8488] ../src/time.c:78
    ruby(eq) ../src/time.c:78
    ruby(small_vtm_sub) ../src/time.c:1523
    ruby(timelocalw+0x23b) [0x567f3e9b] ../src/time.c:1593
    ruby(time_s_alloc+0x0) [0x567f536b] ../src/time.c:3698
    ruby(time_new_timew) ../src/time.c:2694
    ruby(time_s_mktime) ../src/time.c:3698



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