From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Joseph Myers <joseph@codesourcery.com>
Cc: "Cristian Rodríguez" <crrodriguez@opensuse.org>,
libc-alpha@sourceware.org
Subject: Re: [PATCH 2/2] linux: posix_spawn: return EINVAL on argc < 1
Date: Fri, 28 Jan 2022 20:05:17 -0300 [thread overview]
Message-ID: <fdaff035-8279-fd69-3e14-d4a772a3ac9b@linaro.org> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2201281753070.658852@digraph.polyomino.org.uk>
On 28/01/2022 15:03, Joseph Myers wrote:
> On Fri, 28 Jan 2022, Adhemerval Zanella via Libc-alpha wrote:
>
>> Since Linux is discussing changing on execve syscall [1], I think it would be
>> better to the same not only for posix_spawn, but rather to all execve
>> functions.
>>
>> And since all ends up calling execve, even posix_spawn, I think it would be
>> better to:
>>
>> 1. Make posix/execve.c call __execveat.
>> 1.1. It would also allow remove the Hurd implementation 'sysdeps/mach/hurd/execve.c'
>> 2. Add the proper check on generic, Linux, and Hurd implementation execveat.
>> 2.1. Maybe even add __execveat_internal that just issue the syscall and let the
>> generic wrapper handle the argument parsing.
>> 3. Add a regression test.
>>
>> I also think returning EINVAL is better than the kernel EFAULT one (it
>> seems that the last message on thread does settle for that).
>
> Apart from the need for a test, a note under "Deprecated and removed
> features, and other changes affecting compatibility" in NEWS, and
> documentation in the manual if there's an appropriate place for it to go
> (there is for execve; posix_spawn isn't documented in the manual at all),
We can add a note on deprecated and removed features, but I am not sure
if would make any difference now that kernels will changes the semantic
anyway and it will cause compatibility issues anyway.
> I'd also think it would be better in terms of application compatibility to
> construct an array { pathname, NULL } and pass that in place of argv when
> argv[0] is NULL (*not* when argv[0] is an empty string, I don't see a
> problem with an empty string there), rather than returning an error.
I am really not sure about keeping compatibility here, applications running
on newer kernels with older glibc will need to handle it anyway and I think
it is good move forward to mask this wrong usage. Also, other system already
explicit disallow it, so it is a good indication that portable programs should
not rely on this behavior.
> That's more similar in spirit to what we do with reopening fds 0, 1, 2 if
> not open at startup (but I'd also tend to think the kernel is a better
> place than libc to deal with this, given that anything the *calling*
> program does in userspace with execve can't avoid security issues in the
> *called* program with NULL argv[0] - in the case of fds 0, 1, 2 glibc is
> addressing the problem state directly in the *called* process).
>
> I don't think the "should" in the POSIX specification of posix_spawn is
> very relevant as a justification for the patch (it only requires things
> for Strictly Conforming POSIX Applications).
>
next prev parent reply other threads:[~2022-01-28 23:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-28 13:39 Cristian Rodríguez
2022-01-28 15:26 ` Cristian Rodríguez
2022-01-28 17:07 ` Adhemerval Zanella
2022-01-28 18:03 ` Joseph Myers
2022-01-28 23:05 ` Adhemerval Zanella [this message]
2022-01-28 23:26 ` Joseph Myers
2022-01-28 23:35 ` Cristian Rodríguez
2022-01-28 23:49 ` Joseph Myers
2022-01-29 1:04 ` Cristian Rodríguez
2022-03-23 14:40 ` Cristian Rodríguez
2022-01-28 19:08 ` Cristian Rodríguez
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