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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 10 Apr 2017 23:10:19 -0700
Message-ID: <CA+55aFzB6kv5Ai4M=2BXu9fxGbP_TZvNEG0QN5BNhPS+-XqHrw@mail.gmail.com>
Subject: Re: [git pull] vfs fixes
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
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Hey Al,
 mind looking at fs/namei,c line 2186:

                if (likely(!nd_jump_root(nd)))
                        return s;
                nd->root.mnt = NULL;
-->             rcu_read_unlock();   <--
                return ERR_PTR(-ECHILD);

because that rcu_read_unlock() looks odd.

It looks odd because the lock part is

                if (flags & LOOKUP_RCU)
                        rcu_read_lock();

ie it's locked conditionally, and the code in between does not seem to
return every time LOOKUP_RCU is clear.

So mind giving this a look? Is it as obviously buggy as I think it is,
or is there something I'm missing?

              Linus