From: Aleksa Sarai <asarai@suse.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Song Liu <songliubraving@fb.com>,
linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Alexei Starovoitov <ast@kernel.org>,
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Tycho Andersen <tycho@tycho.ws>,
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Andrew Morton <akpm@linux-foundation.org>,
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Martin KaFai Lau <kafai@fb.com>
Subject: Re: [PATCH v16 06/12] namei: LOOKUP_NO_XDEV: block mountpoint crossing
Date: Sun, 17 Nov 2019 04:24:15 +1100 [thread overview]
Message-ID: <20191116172415.brmuonasi3ef6leg@yavin.dot.cyphar.com> (raw)
In-Reply-To: <20191116010144.GY26530@ZenIV.linux.org.uk>
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On 2019-11-16, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Sat, Nov 16, 2019 at 11:27:56AM +1100, Aleksa Sarai wrote:
>
> > @@ -1383,6 +1398,8 @@ static int follow_dotdot_rcu(struct nameidata *nd)
> > return -ECHILD;
> > if (&mparent->mnt == nd->path.mnt)
> > break;
> > + if (unlikely(nd->flags & LOOKUP_NO_XDEV))
> > + return -EXDEV;
> > /* we know that mountpoint was pinned */
> > nd->path.dentry = mountpoint;
> > nd->path.mnt = &mparent->mnt;
> > @@ -1397,6 +1414,8 @@ static int follow_dotdot_rcu(struct nameidata *nd)
> > return -ECHILD;
> > if (!mounted)
> > break;
> > + if (unlikely(nd->flags & LOOKUP_NO_XDEV))
> > + return -EXDEV;
> > nd->path.mnt = &mounted->mnt;
> > nd->path.dentry = mounted->mnt.mnt_root;
> > inode = nd->path.dentry->d_inode;
>
> I really don't think we should return hard errors from that function.
> Let the caller redo it in refwalk mode.
I suspected as much, though my reason for not changing it was that the
mount_lock check should ensure that the cached status of whether ".." is
a mountpoint crossing is correct. But I guess this is more about being
safe than sorry, rather than an actual bug?
> It's not the fast path, especially for this kind of errors. Matter of
> fact, I'm not sure about -ENOENT returned in another failure case
> there - it's probably OK, but again, -ECHILD would be just as good.
I can switch the -ENOENT too if you like.
--
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>
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next prev parent reply other threads:[~2019-11-16 17:45 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-16 0:27 [PATCH v16 00/12] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 01/12] nsfs: clean-up ns_get_path() signature to return int Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 02/12] namei: allow nd_jump_link() to produce errors Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:37 ` Al Viro
2019-11-16 0:37 ` Al Viro
2019-11-16 18:09 ` Aleksa Sarai
2019-11-16 18:09 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 03/12] namei: allow set_root() " Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 04/12] namei: LOOKUP_NO_SYMLINKS: block symlink resolution Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 05/12] namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 06/12] namei: LOOKUP_NO_XDEV: block mountpoint crossing Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 1:01 ` Al Viro
2019-11-16 17:24 ` Aleksa Sarai [this message]
2019-11-16 0:27 ` [PATCH v16 07/12] namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 08/12] namei: LOOKUP_IN_ROOT: chroot-like " Aleksa Sarai
2019-11-16 0:27 ` Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 09/12] namei: LOOKUP_{IN_ROOT, BENEATH}: permit limited ".." resolution Aleksa Sarai
2019-11-16 0:27 ` [PATCH v16 09/12] namei: LOOKUP_{IN_ROOT,BENEATH}: " Aleksa Sarai
2019-11-16 1:03 ` Al Viro
2019-11-16 16:38 ` Aleksa Sarai
2019-11-16 0:28 ` [PATCH v16 10/12] open: introduce openat2(2) syscall Aleksa Sarai
2019-11-16 0:28 ` Aleksa Sarai
2019-11-16 0:28 ` [PATCH v16 11/12] selftests: add openat2(2) selftests Aleksa Sarai
2019-11-16 0:28 ` Aleksa Sarai
2019-11-16 0:28 ` [PATCH v16 12/12] Documentation: path-lookup: include new LOOKUP flags Aleksa Sarai
2019-11-16 0:28 ` Aleksa Sarai
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