Date: Wed, 27 Jul 2005 20:01:52 -0400 (EDT) From: William Josephson <freebsd-D20050727@morphisms.net> To: freebsd-current@FreeBSD.org Subject: dlinfo/rtld.c bug Message-ID: <20050728000152.871E026@mero.morphisms.net>
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I've run across a bug in the ELF dynamic linker in FreeBSD 4.x
and FreeBSD 5.4. Although I haven't had a chance to compile or
install FreeBSD 6 yet, the bug appears to be in the ELF dynamic
linker in at least FreeBSD 4 through -CURRENT. The problem is
that do_search_info in libexec/rtld-elf/rtld.c does not account
for the space required by Dl_serpath structures with either the
RTLD_DI_SERINFOSIZE, or the RTLD_DI_SERINFO requests. The
example program in the dlinfo man page happens to work, but a
simple loop copying the path strings into a buffer allocated with
malloc will corrupt the heap. The program below illustrates the
problem. Given that the arithmetic in do_search_info is easily
fixed, it might be worth patching before the upcoming release.
#include <link.h>
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
char *s;
Dl_serinfo *p;
Dl_serinfo info;
memset(&info, 0, sizeof(info));
dlinfo(RTLD_SELF, RTLD_DI_SERINFOSIZE, (void*)&info);
p = malloc(info.dls_size);
memset(p, 0, info.dls_size);
p->dls_cnt = info.dls_cnt;
p->dls_size = info.dls_size;
dlinfo(RTLD_SELF, RTLD_DI_SERINFO, (void*)p);
s = p->dls_serpath[p->dls_cnt-1].dls_name;
s += strlen(s)+1;
printf("%d %d %d %d %d\n", info.dls_size, (char*)s-(char*)p,
((char*)s-(char*)p)-info.dls_size, sizeof(Dl_serpath),
info.dls_cnt*sizeof(Dl_serpath));
return 0;
}
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