linux-kernel - Re: [PATCH 1/2] pipe: Remove assertion from pipe

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Message-ID: <CAHk-=wgBLUeMUwfWGfqeihz4K=QhXxEgskOo6aUfTmLa=XMvzQ@mail.gmail.com>
Date:   Thu, 5 Dec 2019 09:42:06 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Eric Biggers <ebiggers@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] pipe: Remove assertion from pipe_poll()

On Thu, Dec 5, 2019 at 9:21 AM David Howells <dhowells@...hat.com> wrote:
>
> An assertion check was added to pipe_poll() to make sure that the ring
> occupancy isn't seen to overflow the ring size.  However, since no locks
> are held when the three values are read, it is possible for F_SETPIPE_SZ to
> intervene and muck up the calculation, thereby causing the oops.
>
> Fix this by simply removing the assertion and accepting that the
> calculation might be approximate.

This is not what the patch actually does.

The patch you sent only adds the wakeup when the pipe size changes.

Please re-generate both patches and re-send.

              Linus