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From: Mike Gilbert <floppym@gentoo.org>
To: musl@lists.openwall.com
Cc: "Michael Gilbert (floppym)" <floppym@gentoo.org>
Subject: [musl] faccessat behavior on old kernels (<5.8)
Date: Mon, 19 Jun 2023 14:14:39 -0400	[thread overview]
Message-ID: <CAJ0EP43QiTHZMsmLFrE5qFCgyq+FE7QSk=povbPT-VjF=FEusA@mail.gmail.com> (raw)

I am not subscribed, so please CC me on replies.

I received a bug report on Gentoo Linux.

https://bugs.gentoo.org/908765

There appears to be a difference in behavior between musl and glibc
when running on Linux kernels that lack support for the faccessat2
system call.

On glibc, the following call returns 0. On musl, it returns -1 and
sets errno to EINVAL.

faccessat(AT_FDCWD, "/dev/null", F_OK, AT_SYMLINK_NOFOLLOW);

On older kernels, the underlying faccessat2 syscall returns -1 / ENOSYS.
glibc follows that up with an fstatat64 with equivalent arguments.
musl immediately fails with -1 / EINVAL.

Relevant code:

https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/faccessat.c;h=0ccbd778b5f4d61f9121b6aeb59782c21ae647a0;hb=a704fd9a133bfb10510e18702f48a6a9c88dbbd5#l36

https://git.musl-libc.org/cgit/musl/tree/src/unistd/faccessat.c?h=v1.2.4#n34

             reply	other threads:[~2023-06-19 18:28 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-06-19 18:14 Mike Gilbert [this message]
2023-06-19 21:49 ` Gabriel Ravier
2023-06-19 23:59   ` Rich Felker
2023-06-20  0:52     ` Mike Gilbert
2023-06-20  1:25       ` Rich Felker

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