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List:       opensuse-factory
Subject:    Re: FORTIFY_SOURCE=3
From:       Martin_Liška <mliska () suse ! cz>
Date:       2022-05-16 6:44:48
Message-ID: e9237547-526d-1a0f-3d95-b34ee721bb4a () suse ! cz
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On 5/14/22 00:48, Aaron Puchert wrote:
> Am 13.05.22 um 15:19 schrieb Dominique Leuenberger / DimStar:
> > * Attempting to build the distro using FORTIFY_SOURCE=3 instead of
> > FORTIFY_SOURCE=2
> 
> Is that really a good default though? The RedHat blog [1] writes
> 
> > Earlier _FORTIFY_SOURCE levels rely on constant object sizes; because
> > of this, the runtime overhead is negligible. _FORTIFY_SOURCE=3,
> > however, changes that because expressions used to compute the object
> > size can be arbitrarily complex. Complex expressions can add
> > arbitrarily more runtime overhead. Further, consider the possibility
> > of do_something in the previous example being called in a loop; the
> > overhead gets magnified.

Hi.

We hope the overhead will be reasonable even though it's not so constant
as FS=2. If there are affected packages, we can drop the fortification level
for them.

Martin

> This was a good enough reason to not sneak
> > this new functionality in under the hood. The new level lets
> > developers tinker around with it and decide whether the overhead was
> > acceptable for their use case.
> 
> [1] <https://developers.redhat.com/blog/2021/04/16/broadening-compiler-checks-for-buffer-overflows-in-_fortify_source#what_s_next_for__fortify_source>
> 


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