Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

[Florian Weimer]

* Paul Eggert:

> On 3/10/20 12:30 PM, Florian Weimer wrote:
>> The glibc implementation needs /proc to avoid the race.  There is no
>> way around that, otherwise we introduce a security vulnerability.
>
> It is unfortunate that we have dueling paranoia here. coreutils mknod is 
> paranoid so it uses lchmod to avoid a race, and then glibc lchmod is paranoid 
> so 
> it refuses to work with lchmod unless /proc is mounted.

I now wonder if neither gnulib nor glibc should pretend that they can
implement lchmod and fchmodat on Linux in a usable fashion.

I added the emulation to glibc mostly because it was in gnulib.
Otherwise, I would have insisted that a proper system call be
implemented first.