From: Andy Lutomirski <luto@amacapital.net>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Willy Tarreau <w@1wt.eu>, Ingo Molnar <mingo@kernel.org>,
"security@kernel.org" <security@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Brad Spengler <spender@grsecurity.net>
Subject: Re: [RFC PATCH] fs: Add user_file_or_path_at and use it for truncate
Date: Tue, 27 Aug 2013 16:13:12 -0700 [thread overview]
Message-ID: <CALCETrWi7_ObM58oeSUahzvNVsrjGSgsqfRSXWoUcEpYVby=Ng@mail.gmail.com> (raw)
In-Reply-To: <20130827230827.GI27005@ZenIV.linux.org.uk>
On Tue, Aug 27, 2013 at 4:08 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Tue, Aug 27, 2013 at 12:16:34PM -0700, Andy Lutomirski wrote:
>> This is an experiment to see if we can get nice semantics for all syscalls
>> that either follow symlinks or allow AT_EMPTY_PATH without jumping through
>> enormous hoops. This converts truncate (although you can't tell using
>> truncate from coreutils, because it actually uses open + ftruncate).
>>
>> The basic idea is that there's a new helper function
>> user_file_or_path_at. It takes an fd and a path and, depending on
>> flags, the emptiness of the path, and whether path is a magic /proc
>> symlink (or a symlink to a magic /proc/symlink), it returns either a
>> struct path or a struct file *.
>
> No.
I'm curious what's wrong with the general concept. (I agree that the
implementation is heinous.)
If I ever wanted to add a new *at syscall, I'd like to be able to do:
int sys_whateverat(int dfd, const char __user *name, int flags)
{
resolve_the_thing(dfd, name, flags);
if (it's a file) {
check fmode;
} else {
inode_permission();
}
actually_do_something(inode);
unreference_whatever_i_got();
return ret;
}
thereby killing the fwhatever and whateverat birds with one stone.
>
>> + path_get(&nd->path);
>> + if (nd->flags & LOOKUP_FILE) {
>> + if (nd->last_symlink_file)
>> + fput(nd->last_symlink_file);
>> + nd->last_symlink_file = file;
>
> This is ugly (and costs quite a bit of overhead)
>
>> -static int proc_cwd_link(struct dentry *dentry, struct path *path)
>> +static int proc_cwd_link(struct dentry *dentry, struct file_or_path *link)
>
> ... and this is even more vile. Vetoed, for being too ugly to live.
...phew. I wasn't looking forward to testing and debugging my crap :)
--Andy
next prev parent reply other threads:[~2013-08-27 23:13 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-21 19:14 [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY_PATH) Andy Lutomirski
[not found] ` <CA+55aFxi-ps2f2M8xPhfbuQ0pToqupPrDsLi2+GPUK2sqdYfUw@mail.gmail.com>
[not found] ` <CALCETrW7+LcexA6v6RQDKhni_yJAduOmiSDneCpq3v8sPDvwUQ@mail.gmail.com>
2013-08-21 20:16 ` Willy Tarreau
2013-08-22 18:48 ` Linus Torvalds
2013-08-22 18:53 ` Willy Tarreau
2013-08-22 19:05 ` Andy Lutomirski
2013-08-22 19:23 ` Linus Torvalds
2013-08-22 20:10 ` Andy Lutomirski
2013-08-22 20:15 ` Willy Tarreau
2013-08-22 20:22 ` Andy Lutomirski
2013-08-22 20:44 ` Linus Torvalds
2013-08-22 20:48 ` Andy Lutomirski
2013-08-22 20:54 ` Linus Torvalds
2013-08-22 20:58 ` Andy Lutomirski
2013-08-23 1:07 ` Al Viro
2013-08-25 3:37 ` Al Viro
2013-08-25 7:26 ` Andy Lutomirski
2013-08-25 14:23 ` Al Viro
2013-08-25 17:04 ` Andy Lutomirski
2013-08-25 19:57 ` Linus Torvalds
2013-08-25 20:06 ` Al Viro
2013-08-25 20:23 ` Linus Torvalds
2013-08-26 17:37 ` Linus Torvalds
2013-08-26 18:07 ` Linus Torvalds
2013-08-26 18:11 ` Andy Lutomirski
2013-08-27 19:16 ` [RFC PATCH] fs: Add user_file_or_path_at and use it for truncate Andy Lutomirski
2013-08-27 19:32 ` Linus Torvalds
2013-08-27 20:28 ` Andy Lutomirski
2013-08-28 6:16 ` Al Viro
2013-08-28 16:24 ` Linus Torvalds
2013-08-28 19:04 ` Andy Lutomirski
2013-08-28 19:59 ` Al Viro
2013-08-28 21:07 ` Andy Lutomirski
2013-08-27 23:08 ` Al Viro
2013-08-27 23:13 ` Andy Lutomirski [this message]
2013-08-24 18:29 ` /proc/pid/fd && anon_inode_fops Oleg Nesterov
2013-08-24 21:24 ` Willy Tarreau
2013-08-25 5:23 ` Al Viro
2013-08-25 6:50 ` Willy Tarreau
2013-08-25 18:51 ` Linus Torvalds
2013-08-25 19:48 ` Oleg Nesterov
2013-08-25 20:05 ` Linus Torvalds
2013-08-26 15:33 ` Oleg Nesterov
2013-08-26 16:37 ` Oleg Nesterov
2013-08-26 17:54 ` [PATCH] proc: make proc_fd_permission() thread-friendly Oleg Nesterov
2013-08-26 18:09 ` Linus Torvalds
2013-08-26 19:35 ` Linus Torvalds
2013-08-26 20:20 ` Willy Tarreau
2013-08-27 15:05 ` Oleg Nesterov
2013-08-27 14:39 ` [PATCH 0/1] proc: make /proc/self point to thread Oleg Nesterov
2013-08-27 14:40 ` [PATCH 1/1] " Oleg Nesterov
2013-08-27 16:39 ` Linus Torvalds
2013-08-27 17:49 ` Oleg Nesterov
2013-08-27 18:15 ` Linus Torvalds
2013-08-27 18:28 ` Oleg Nesterov
[not found] ` <CALCETrXP-mYBPRon=0NzexW1FK1Qxz2+Bwv7-WeHBQpvW7ywRg@mail.gmail.com>
2013-08-27 15:45 ` [PATCH] proc: make proc_fd_permission() thread-friendly Oleg Nesterov
2013-08-26 18:32 ` Eric W. Biederman
2013-08-26 18:46 ` Oleg Nesterov
2013-08-26 18:56 ` Oleg Nesterov
2013-08-26 19:10 ` Eric W. Biederman
2013-08-27 14:53 ` Oleg Nesterov
2013-08-25 18:32 ` /proc/pid/fd && anon_inode_fops Linus Torvalds
2013-08-25 19:11 ` Al Viro
2013-08-25 19:17 ` Andy Lutomirski
2013-09-03 15:58 ` Pavel Machek
2013-08-25 15:45 ` Oleg Nesterov
2013-08-22 19:39 ` [PATCH v2] vfs: Tighten up linkat(..., AT_EMPTY_PATH) Willy Tarreau
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