linux-kernel - Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets.

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Message-Id: <201908220742.x7M7gQJW078160@www262.sakura.ne.jp>
Date:   Thu, 22 Aug 2019 16:42:26 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
        syzbot <syzbot+0341f6a4d729d4e0acf1@...kaller.appspotmail.com>,
        jmorris@...ei.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, serge@...lyn.com,
        syzkaller-bugs@...glegroups.com, takedakn@...data.co.jp,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2] tomoyo: Don't check open/getattr permission on sockets.

Eric Biggers wrote:
> On Thu, Aug 22, 2019 at 03:55:31PM +0900, Tetsuo Handa wrote:
> > > Also, isn't the same bug in other places too?:
> > > 
> > > 	- tomoyo_path_chmod()
> > > 	- tomoyo_path_chown()
> > > 	- smack_inode_getsecurity()
> > > 	- smack_inode_setsecurity()
> > 
> > What's the bug? The file descriptor returned by open(O_PATH) cannot be
> > passed to read(2), write(2), fchmod(2), fchown(2), fgetxattr(2), mmap(2) etc.
> > 
> 
> chmod(2), chown(2), getxattr(2), and setxattr(2) take a path, not a fd.
> 

OK. Then, is the correct fix

  inode_lock(inode);
  if (SOCKET_I(inode)->sk) {
    // Can access SOCKET_I(sock)->sk->*
  } else {
    // Already close()d. Don't touch.
  }
  inode_unlock(inode);

thanks to

  commit 6d8c50dcb029872b ("socket: close race condition between sock_close() and sockfs_setattr()")
  commit ff7b11aa481f682e ("net: socket: set sock->sk to NULL after calling proto_ops::release()")

changes?