Date: Tue, 8 Nov 2016 16:13:24 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Christoph Hellwig <hch@infradead.org>
Cc: Richard Weinberger <richard@nod.at>, drbd-dev@lists.linbit.com,
        linux-kernel@vger.kernel.org, lars.ellenberg@linbit.com,
        philipp.reisner@linbit.com, stable@vger.kernel.org,
        christoph.lechleitner@iteg.at, wolfgang.glas@iteg.at
Subject: Re: [PATCH] drbd: Fix kernel_sendmsg() usage
Message-ID: <20161108161324.GH19539@ZenIV.linux.org.uk>
References: <1478601789-15060-1-git-send-email-richard@nod.at>
 <20161108154924.GA19063@infradead.org>
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On Tue, Nov 08, 2016 at 07:49:24AM -0800, Christoph Hellwig wrote:
> On Tue, Nov 08, 2016 at 11:43:09AM +0100, Richard Weinberger wrote:
> > Don't pass a size larger than iov_len to kernel_sendmsg().
> > Otherwise it will cause a NULL pointer deref when kernel_sendmsg()
> > returns with rv < size.
> > 
> > Although the issue exists since day 0, only on non-ancient kernels
> > that contain change 57be5bdad759 ("ip: convert tcp_sendmsg() to iov_iter
> > primitives") it seems to trigger [0][1][2][3][4].
> 
> The real fix here is to convert it to the right primitive, e.g. take
> Al's patch from here:
> 
> https://git.kernel.org/cgit/linux/kernel/git/viro/vfs.git/commit/?h=work.sendmsg&id=7a4992299554a9e1ed3c4540bcfa9e40aa9a6376

_After_ the backport-friendly part, please.  And that's my ACK-by
on Richard's variant.