linux-kernel - Re: [PATCH 01/14] VFS: Add additional RESOLVE

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Date:   Mon, 9 Mar 2020 21:56:18 +0100
From:   Stefan Metzmacher <metze@...ba.org>
To:     David Howells <dhowells@...hat.com>, torvalds@...ux-foundation.org,
        viro@...iv.linux.org.uk
Cc:     Aleksa Sarai <cyphar@...har.com>, raven@...maw.net,
        mszeredi@...hat.com, christian@...uner.io, jannh@...gle.com,
        darrick.wong@...cle.com, kzak@...hat.com, jlayton@...hat.com,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/14] VFS: Add additional RESOLVE_* flags [ver #18]

Hi David,

> Add additional RESOLVE_* flags to correspond to AT_* flags that aren't
> currently implemented:
> 
> 	RESOLVE_NO_TRAILING_SYMLINKS    for AT_SYMLINK_NOFOLLOW
> 	RESOLVE_NO_TRAILING_AUTOMOUNTS  for AT_NO_AUTOMOUNT
> 	RESOLVE_EMPTY_PATH              for AT_EMPTY_PATH

Thanks for changing the names!

> This is necessary for fsinfo() to use RESOLVE_* flags instead of AT_* flags
> if the latter are to be considered deprecated for new system calls.
> 
> Also make openat2() handle RESOLVE_NO_TRAILING_SYMLINKS.
> 
> Automounting is currently forced by doing an open(), so adding support to
> openat2() for RESOLVE_NO_TRAILING_AUTOMOUNTS is not trivial.

lookup_flags &= ~LOOKUP_AUTOMOUNT won't work?

At least it should cause EINVAL (or something similar) instead of being
silently ignored. The same applies to RESOLVE_EMPTY_PATH, it should be
handled with some logic or also cause EINVAL.

vfs_statx()/vfs_stat_set_lookup_flags() seems to have a similar logic
using the AT_* flags.

metze



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