netdev - Re: [PATCH net] mptcp: avoid NULL-ptr derefence on fallback

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Date:   Tue, 26 May 2020 20:18:59 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, mathew.j.martineau@...ux.intel.com,
        kuba@...nel.org, mptcp@...ts.01.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH net] mptcp: avoid NULL-ptr derefence on fallback

From: Paolo Abeni <pabeni@...hat.com>
Date: Mon, 25 May 2020 16:38:47 +0200

> In the MPTCP receive path we must cope with TCP fallback
> on blocking recvmsg(). Currently in such code path we detect
> the fallback condition, but we don't fetch the struct socket
> required for fallback.
> 
> The above allowed syzkaller to trigger a NULL pointer
> dereference:
 ...
> Address the issue initializing the struct socket reference
> before entering the fallback code.
> 
> Reported-and-tested-by: syzbot+c6bfc3db991edc918432@...kaller.appspotmail.com
> Suggested-by: Ondrej Mosnacek <omosnace@...hat.com>
> Fixes: 8ab183deb26a ("mptcp: cope with later TCP fallback")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied and queued up for -stable, thanks.