Re: glibc: SA 12.3 085 / SA 12.4 079

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Am 02.04.26 um 02:14 schrieb "Douglas R. Reno"
([email protected] via lfs-support Mailing List):
> On 3/23/26 3:55 PM, Rainer Fiebig ([email protected] via lfs-support
> Mailing List) wrote:
>> In SA 12.3 085 users are admonished to follow the full
>> glibc-update-procedure detailed in LFS although only a patch within the
>> same version was applied.  This seems a bit excessive to me - or is
>> glibc really that touchy that one cannot even apply a security-patch
>> without risking to ruin one's system?
>>
>> SA 12.4 079 seems a bit more relaxed in this respect as it also provides
>> a patch but doesn't mention the update-procedure.
>>
>> So - who's right here?  And I'm also wondering - probably naively - why
>> updating/upgrading glibc always has to be such a drama - after all they
>> claim that "The GNU C Library is designed to be a backwards compatible,
>> ..."[1].  Thanks.
>>
>> Rainer
>>
>>
>> [1] https://sourceware.org/glibc/
>>
>>
> 
> Hi Rainer,
> 
> Unfortunately the warning there is not excessive. If the update
> procedure is not followed, the system will get broken because 'make
> install' will crash and result in every program on the system returning
> a stack smashing error. This occurs because ld-linux-x86-64.so.2 isn't
> properly replaced because of the way the Makefile performs the
> installation.
> 
> The DESTDIR installation fixes the problem by installing the shared
> libraries first...

Right, so this step is essential.  I have it in my build-instructions
for glibc and the update-process is smooth, except for a little bump:
when I reboot the system, it stops during the shutdown with a message
like "a mount point is busy" or so (need to catch that the next time).
But after hitting "enter" the shutdown continues and everything from
then on is fine and as usual.

> 
> While glibc does advertise complete backwards compatibility, it will
> still fall over itself and break during the installation procedure if
> it's not followed carefully! However, after the procedure is followed,
> existing binaries don't break, so it is backwards compatible in that way :)

Now that is good news.  That the binaries can be expected to continue to
work after a glibc-update is the key-point, I'd say.  It's enough
"backward compatibility" for me and it takes the slight uneasiness out
of an update which otherwise remained for a while - even if one followed
the instructions.

> 
> I noticed that SA-12.4-079 didn't have the warning, so when I filed the
> advisory for SA-13.0-021, I copied the warning over to SA-12.4-079.

Nice.  And thanks for the info!

Rainer


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