Date: Tue, 16 Feb 2016 19:05:27 -0500 From: Hugues Bruant <hugues@...ofs.com> To: musl@...ts.openwall.com Subject: Re: dynlink.c: bug in reclaim_gaps leading to segfault in __libc_exit_fini > > ==59== Invalid free() / delete / delete / realloc() > > ==59== at 0x4C92B0E: free (vg_replace_malloc.c:530) > > ==59== by 0x4056F68: reclaim_gaps (dynlink.c:488) > > ==59== by 0x405743D: map_library (dynlink.c:708) > > ==59== by 0x4057EF3: load_library (dynlink.c:1014) > > ==59== by 0x4058CA8: load_preload (dynlink.c:1112) > > ==59== by 0x4058CA8: __dls3 (dynlink.c:1581) > > ==59== by 0x405856A: __dls2 (dynlink.c:1383) > > ==59== by 0x405655E: ??? (in /lib/ld-musl-x86_64.so.1) > > ==59== by 0x3: ??? > > ==59== by 0xFFF000E3A: ??? > > ==59== by 0xFFF000E3E: ??? > > ==59== by 0xFFF000E44: ??? > > ==59== by 0xFFF000E86: ??? > > > > Afterwards, the program proceeds with no issue, until it exists, at which > > point a segfault is triggered when cleaning up shared libraries: > > > > this is not a bug. How confident of that are you? Something is reliably overwriting 32 bytes of a dso struct. Valgrind supposedly catches out-of-bounds writes to heap-allocated arrays so unless I'm mistaken, the absence of any other errors until the segfault suggests that there is no out-of-bounds write and the logical conclusion is that an allocation overlaps with the corrupted dso struct. The program is not using any threads so if I understand correctly it sohuld not be negatively affected by the small default stack size. In any case, I enabled -fstack-protector-all and -fstack-check and this did not reveal any issue so at this point I'm ruling out stack overflow as the source of the corruption. Quite frankly I'm hoping that the root cause is in libdmg-hfsplus because it would be much easier to fix than musl but the evidence does not point in that direction. Any suggestions for further investigation would be appreciated. Content of type "text/html" skipped
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