Re: [musl] Bug: installed symlinks are unreadable on MacOS

[Tim Cuthbertson <tim@gfxmonk.net>]

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Yeah, setting it to `chmod 000` in just the symlink branch seems good to me
too.

Looking at the script more closely, `mode` is always set and so I'm unclear
why there is also a `umask 077` at all. Whatever permissions we create the
file with, we `chmod` it explicitly before doing anything else.

Is that line just there to undo the potential change to `umask` in the
mkdirp branch? If so, maybe that should be done explicitly by capturing the
old umask? e.g:

if test "$mkdirp" ; then
umaskorig="$(umask)"
umask 022
case "$2" in
*/*) mkdir -p "${dst%/*}" ;;
esac
umask "$umaskorig"
fi


On Thu, 1 Feb 2024 at 00:47, Rich Felker <dalias@libc.org> wrote:

> On Wed, Jan 31, 2024 at 01:30:21PM +1100, Tim Cuthbertson wrote:
> > I'm not subscribed to the mailing list, please CC me on replies.
> >
> > Installed symlinks (specifically ld-musl-x86_64.so.1 have permissions
> 0700
> > on MacOS, which means only the owner (typically root) can read them.
> >
> > Symlink permissions can't be anything but 0777 on Linux, but on Mac they
> > can be set, and in this case are being inherited from the 077 umask in
> > install.sh:
> >
> > ```
> > $ ls -l
> >
> /nix/store/fgkznmnz1swzp8ck75fa2zvj62pkjgvq-musl-x86_64-unknown-linux-musl-1.2.3/lib/ld-musl-x86_64.so.1
> > ls: cannot read symbolic link
> >
> '/nix/store/fgkznmnz1swzp8ck75fa2zvj62pkjgvq-musl-x86_64-unknown-linux-musl-1.2.3/lib/ld-musl-x86_64.so.1':
> > Permission denied
> > lrwx------ 1 root wheel 7 Jan  1  1970
> >
> /nix/store/fgkznmnz1swzp8ck75fa2zvj62pkjgvq-musl-x86_64-unknown-linux-musl-1.2.3/lib/ld-musl-x86_64.so.1
> > ```
> >
> > My fix (attached) is to use `umask 022`, which was already being used to
> > make directories. It's not practical to fix this by specifying the
> intended
> > permissions for this symlink, as setting link permissions requires the
> > nonstandard `-h` chmod flag, which presumably fails on other platforms.
> >
> > First discovered when cross-building on MacOS for linux:
> > https://github.com/NixOS/nixpkgs/issues/285141
> >
> > I've tested the fix works in nix. I am fairly confident the same issue
> > exists outside of Nix given the fix, but I haven't built musl before and
> > ran into unrelated errors.
> >
> > Thanks,
> >  - Tim
>
> Thanks for catching this. Do you think it might be better to put umask
> 000 inside the symlink case instead of just reusing the 022 from dir?
> 000 seems like what you actually want to fix the symlink behavior.
>
> Alternatively maybe we should set umask to the complement of the
> desired mode?
>
> Rich
>

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