Date: Fri, 31 May 2019 00:13:27 -0400 From: sva sva <azharivs@...il.com> To: musl@...ts.openwall.com Subject: Re: Hijacking malloc called within musl libc I am interposing all malloc/calloc/realloc/free/memalign but still the realloc in scandir gets called from musl's libc. Does that make sense? Vahid On Thu, May 30, 2019 at 6:30 PM Szabolcs Nagy <nsz@...t70.net> wrote: > * sva sva <azharivs@...il.com> [2019-05-30 16:39:48 -0400]: > > I am LD_PRELOADing an application my own malloc which eventually calls > the > > libc malloc. Everything is fine until the code hits malloc which is > called > > musl has explicit checks not to allow libc internal malloc > calls if user malloc is used (at least for memalign), > because mixing user malloc and libc malloc is problematic. > > this means that currently the common malloc wrapping methods > don't work on musl. (you can try to copy the musl malloc > implementation into an external library and work with that > instead of calling back to libc malloc, but it might need > some changes) > > > from musl's own libc which doesn't get overloaded. I want those to be > > overloaded as well. > > > > More specifically this is the part of libc for scandir code at > > src/dirent/scandir.c: > > tmp = realloc(names, len * sizeof *names); > > if you define malloc/calloc/realloc/memalign/free then > all musl internal calls to those functions will go to > your definitions (including the realloc in scandir). > > (if you only interpose a subset of the malloc functions > that's broken and cannot work) > > > > > I checked how this works for glibc, and apparently they use > > __libc_malloc/etc. internally and have malloc as a weak alias for that > > which is used every where including the rest of the standard library. > > However in musl, there is no such thing as a weak alias defined for > > malloc/etc. > > > > I am kind of stuck here so would appreciate some help. > > > > Thanks > > > > Vahid > Content of type "text/html" skipped
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