Re: [PATCH] libio: Implement internal function __libc_readline_unlocked

[Carlos O'Donell <carlos at redhat dot com>]

On 07/18/2018 12:54 PM, Joseph Myers wrote:
> On Fri, 6 Jul 2018, Carlos O'Donell wrote:
> 
>> We can change GLIBC_PRIVATE symbols at will. There is no stability
>> guarantee at all.
> 
> With the caveat that GLIBC_PRIVATE interface changes on a release branch 
> are dangerous, because they can affect upgrades on live systems (if a 
> running process started with old glibc, then there was an upgrade, then 
> the running process dlopens a library from the new glibc that depends on a 
> change to a GLIBC_PRIVATE interface provided by libc - see the issues when 
> some distributions tried to backport the CVE-2014-9761 fix).
Agreed, GLIBC_PRIVATE changes on a release branch are dangerous, and this is
not the case here.

I've seen similar problems in the last year with various backports we've done
from stable.

My opinion is that glibc upgrades are not carried out correctly by any of the
distributions, and I've outlined that in the FAQ:
https://sourceware.org/glibc/wiki/FAQ#How_do_I_install_all_of_the_GNU_C_Library_project_libraries_that_I_just_built.3F

I think I can reduce the upgrade race in Fedora by using a single symlink.

-- 
Cheers,
Carlos.