linux-kernel - Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN

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Message-ID: <d65ee15211aa69a815bdc7cc4fc9e7c2e1bcba43.camel@perches.com>
Date:   Sun, 24 May 2020 10:38:02 -0700
From:   Joe Perches <joe@...ches.com>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into
 printk(KERN_DEBUG)

On Sun, 2020-05-24 at 23:50 +0900, Tetsuo Handa wrote:
> syzbot found a NULL pointer dereference bug inside mptcp_recvmsg() due to
> ssock == NULL, but this bug manifested inside selinux_socket_recvmsg()
> because pr_debug() was no-op [1].
> 
>   pr_debug("fallback-read subflow=%p",
>            mptcp_subflow_ctx(ssock->sk));
>   copied = sock_recvmsg(ssock, msg, flags);

> Since console loglevel used by syzkaller will not print KERN_DEBUG
> messages to consoles, always evaluating pr_devel()/pr_debug() messages
> will not cause too much console output. Thus, let's allow fuzzers to
> always evaluate pr_devel()/pr_debug() messages.

While I think this is rather unnecessary,
what about dev_dbg/netdev_dbg/netif_dbg et al ?