linux-kernel - Re: [PATCH] NFC: llcp: fix nfc_llcp_send_ui

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Message-ID: <20180626051221.GC31439@jagdpanzerIV>
Date:   Tue, 26 Jun 2018 14:12:21 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Petr Mladek <pmladek@...e.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        linux-wireless@...r.kernel.org, netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzbot <syzbot+d29d18215e477cfbfbdd@...kaller.appspotmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCH] NFC: llcp: fix nfc_llcp_send_ui_frame() lockup

On (06/26/18 07:07), Dmitry Vyukov wrote:
[..]
> >  #include <net/nfc/nfc.h>
> > @@ -755,7 +756,8 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap,
> >                 pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT,
> >                                          frag_len + LLCP_HEADER_SIZE, &err);
> >                 if (pdu == NULL) {
> > -                       pr_err("Could not allocate PDU\n");
> > +                       pr_err_ratelimited("Could not allocate PDU\n");
> > +                       cond_resched();
> >                         continue;
> >                 }
> 
> 
> But this thread is still in an infinite (unkillable?) loop? If yes, we
> are waiting for the next syzbot report ;)

The loop is still infinite, correct, but we have a preemption point now.
Sure, net people can come with a much better solution, I'll be happy to
scratch my patch.

	-ss