Re: [PATCH] git-compat-util: work around for access(X_OK) under root

From: Junio C Hamano <gitster@pobox.com>
Date: Apr 24, 2019, 00:55 UTC
Message-ID: <xmqqsgu843yv.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20190423235526.GF6316@genre.crustytoothpaste.net>

"brian m. carlson" <sandals@crustytoothpaste.net> writes:

Show 7 quoted lines

> What POSIX says on this is the following:
>
>   If any access permissions are checked, each shall be checked
>   individually, as described in XBD File Access Permissions, except that
>   where that description refers to execute permission for a process with
>   appropriate privileges, an implementation may indicate success for
>   X_OK even if execute permission is not granted to any user.

Do I take this "not granted to any user" as "no +x bit is set for owner, group or other", and "a process with appropriate privileges" as "running as root"?

The latter half feels iffy, if the system is still allowed to fail execution by "a process with appropriate privileges", leading to inconsistent answer from access(2) and behaviour by execv(2). But at least that explains what was observed.

Show 6 quoted lines

> I believe that's what's occurring here. Your commit message, however,
> should contain some text that explains that AIX takes this liberty
> provided by POSIX, and why that causes problems for Git (i.e., what
> problems the user will see). Ideally, the reader of the commit message
> will know the relevant details about this issue from your commit message
> without needing to consult the standard itself.

Very true.

Thanks.