linux-kernel - Re: [PATCH] staging: lustre: ldlm: use designated initializers

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Message-ID: <alpine.LFD.2.20.1612191614320.25173@casper.infradead.org>
Date:   Mon, 19 Dec 2016 16:22:58 +0000 (GMT)
From:   James Simmons <jsimmons@...radead.org>
To:     Kees Cook <keescook@...omium.org>
cc:     linux-kernel@...r.kernel.org, Oleg Drokin <oleg.drokin@...el.com>,
        Andreas Dilger <andreas.dilger@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "John L. Hammond" <john.hammond@...el.com>,
        Emoly Liu <emoly.liu@...el.com>,
        Vitaly Fertman <vitaly_fertman@...atex.com>,
        Bruno Faccini <bruno.faccini@...el.com>,
        Bruce Korb <bruce.korb@...il.com>,
        lustre-devel@...ts.lustre.org, devel@...verdev.osuosl.org
Subject: Re: [PATCH] staging: lustre: ldlm: use designated initializers


> Prepare to mark sensitive kernel structures for randomization by making
> sure they're using designated initializers. These were identified during
> allyesconfig builds of x86, arm, and arm64, with most initializer fixes
> extracted from grsecurity.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/staging/lustre/lustre/ldlm/ldlm_flock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c b/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
> index 722160784f83..f815827532dc 100644
> --- a/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
> +++ b/drivers/staging/lustre/lustre/ldlm/ldlm_flock.c
> @@ -143,7 +143,7 @@ static int ldlm_process_flock_lock(struct ldlm_lock *req, __u64 *flags,
>  	int added = (mode == LCK_NL);
>  	int overlaps = 0;
>  	int splitted = 0;
> -	const struct ldlm_callback_suite null_cbs = { NULL };
> +	const struct ldlm_callback_suite null_cbs = { };
>  
>  	CDEBUG(D_DLMTRACE,
>  	       "flags %#llx owner %llu pid %u mode %u start %llu end %llu\n",

Nak. Filling null_cbs with random data is a bad idea. If you look at 
ldlm_lock_create() where this is used you have

if (cbs) {
	lock->l_blocking_ast = cbs->lcs_blocking;
	lock->l_completion_ast = cbs->lcs_completion;
	lock->l_glimpse_ast = cbs->lcs_glimpse;
}

Having lock->l_* point to random addresses is a bad idea.
What really needs to be done is proper initialization of that
structure. A bunch of patches will be coming to address this.