[PATCH] elf: Remove __libc_enable_secure_decided
Fāng-ruì Sòng
maskray@google.com
Mon Apr 18 23:49:50 GMT 2022
On Mon, Apr 18, 2022 at 3:00 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Fangrui Song:
>
> > No functional change. __libc_enable_secure_decided is always 0 since
> > 73fc4e28b9464f0e13edc719a5372839970e7ddb.
> > ---
> > elf/enbl-secure.c | 7 ++-----
> > include/unistd.h | 1 -
> > 2 files changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/elf/enbl-secure.c b/elf/enbl-secure.c
> > index aa2a0bd877..6a0a6d0f0f 100644
> > --- a/elf/enbl-secure.c
> > +++ b/elf/enbl-secure.c
> > @@ -26,15 +26,12 @@
> > #include <startup.h>
> > #include <libc-internal.h>
> >
> > -/* If nonzero __libc_enable_secure is already set. */
> > -int __libc_enable_secure_decided;
> > /* Safest assumption, if somehow the initializer isn't run. */
> > int __libc_enable_secure = 1;
> >
> > void
> > __libc_init_secure (void)
> > {
> > - if (__libc_enable_secure_decided == 0)
> > - __libc_enable_secure = (startup_geteuid () != startup_getuid ()
> > - || startup_getegid () != startup_getgid ());
> > + __libc_enable_secure = (startup_geteuid () != startup_getuid ()
> > + || startup_getegid () != startup_getgid ());
> > }
>
> Thanks for catching this in time before a release, this would have
> turned into a minor security vulnerability.
>
> __libc_init_secure should not overwrite __libc_enable_secure on Linux
> because _dl_aux_init in dl-support.c already initializes it, and the
> real vs effective check does not always yield the right results (it
> exits AT_SECURE mode for a pure capabilities-based transition, for
> example).
>
> Hurd already overrides __libc_init_secure with an empty function. I
> think we should remove it completely. Then we can also simply
> <startup.h> a bit, I think. Would you be able to write a patch along
> those lines, or should I work on this?
>
> Thanks,
> Florian
>
Thanks for the analysis! I debugged it a bit and understand it better now.
Sent https://sourceware.org/pipermail/libc-alpha/2022-April/137942.html
for clean-up.
--
宋方睿
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