On Sat, 30 Aug 2025 at 00:33, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> So... Siddhesh, could you clarify the claim about breaking getmntent(3)?
> Does it or does it not happen on every system that has readonly AFS
> volumes mounted?
Hmm. Looking at various source trees using Debian code search, at
least dietlibc doesn't treat '#' specially at all.
And glibc seems to treat only a line that *starts* with a '#'
(possibly preceded by space/tab combinations) as an empty line.
klibc checks for '#' at the beginning of the file (without any
potential space skipping before)
Busybox seems to do the same "skip whitespace, then skip lines
starting with '#'" that glibc does.
So I think the '#'-escaping logic is wrong. We should only escape '#'
marks at the beginning of a line (since we already escape spaces and
tabs, the "preceded by whitespace" doesn't matter).
And that means that we shouldn't do it in 'mangle()' at all - because
it's irrelevant for any field but the first.
And the first field in /proc/mounts is that 'r->mnt_devname' (or
show_devname), and again, that should only trigger on the first
character, not every character.
Now, could there be other libraries that get this even worse wrong? Of
course. But
Linus
