[PATCH] io: statx, fstatat64: allow using NULL as path

[Sam James]

Sam James <sam@gentoo.org> writes:

> On Wed, 25 Sep 2024 22:23:14 +0800, Xi Ruoyao wrote:
>>> [...]
>>  I'd suggest to separate this into two patches.  The first one drops the
>> __nonnull(...) on the path, the second one implements the fallback.  The
>> first patch would be so obvious to be applied then.
>
> Paul has fixed this today in gnulib:
>
> commit 6db27b4dd36eda618db20e997ff56bbed7fce3cb
> Author:     Paul Eggert <eggert@cs.ucla.edu>
> AuthorDate: Tue Jun 16 09:45:39 2026 -0700
> Commit:     Paul Eggert <eggert@cs.ucla.edu>
> CommitDate: Tue Jun 16 09:53:22 2026 -0700
>
>     fstatat etc.: fix wrong machine code for calls
>
>     Without this fix, compilers can generate incorrect machine code
>     for functions that call to fstatat-like functions, as the
>     compilers incorrectly assume that the calls’ arguments cannot be
>     null pointers.  This assumption became false with the release of
>     Linux kernel 6.11 (2024).
>     * lib/sys_stat.in.h (fchmodat, fstatat, utimensat):
>     * lib/unistd.in.h (faccessat, fchownat): Do not mark file args
>     with _GL_ARG_NONNULL, as the args are allowed to be null pointers
>     in Linux kernel 6.11+, possibly with glibc 2.41+ involved.
>
> Miao Wang, do you intend to pursue this patch, or Paul, do you intend to
> submit a similar change (the attribute fix is what I care about, anyway)
> on the glibc side? If not, I can look at syncing it.

Ah, I see we had:

commit 55618e13968a60b89e5b226a23afaa8f17c5ef48
Author:     Miao Wang <shankerwangmiao@gmail.com>
AuthorDate: Mon Dec 23 10:30:43 2024 +0100
Commit:     Florian Weimer <fweimer@redhat.com>
CommitDate: Mon Dec 23 10:30:43 2024 +0100

    io: statx, fstatat: Drop nonnull attribute on the path argument

    Since Linux 6.11 the kernel allows path to be NULL if flags &
    AT_EMPTY_PATH.  Let's allow users to take the advantage if they don't
    care running on old kernels.

    Signed-off-by: Miao Wang <shankerwangmiao@gmail.com>
    Signed-off-by: Xi Ruoyao <xry111@xry111.site>
    Reviewed-by: Florian Weimer <fweimer@redhat.com>

But say, fchmodat is still wrong in io/sys/stat.h.

>
> sam
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