linux-kernel - Re: [PATCH] lightnvm: pblk: Fix two sleep-in-atomic-context bugs in pblk_line_submit_smeta

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Message-ID: <cbff381f-c2c7-5656-b121-eb1ec3c75da4@lightnvm.io>
Date:   Tue, 4 Sep 2018 12:11:51 +0200
From:   Matias Bjørling <mb@...htnvm.io>
To:     baijiaju1990@...il.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        javier@...xlabs.com, hans.holmberg@...xlabs.com
Subject: Re: [PATCH] lightnvm: pblk: Fix two sleep-in-atomic-context bugs in
 pblk_line_submit_smeta_io()

On 09/01/2018 01:53 PM, Jia-Ju Bai wrote:
> The driver may sleep with holding a spinlock.
> 
> The function call paths (from bottom to top) in Linux-4.16 are:
> 
> [FUNC] nvm_dev_dma_alloc(GFP_KERNEL)
> drivers/lightnvm/pblk-core.c, 754:
> 	nvm_dev_dma_alloc in pblk_line_submit_smeta_io
> drivers/lightnvm/pblk-core.c, 1048:
> 	pblk_line_submit_smeta_io in pblk_line_init_bb
> drivers/lightnvm/pblk-core.c, 1434:
> 	pblk_line_init_bb in pblk_line_replace_data
> drivers/lightnvm/pblk-recovery.c, 980:
> 	pblk_line_replace_data in pblk_recov_l2p
> drivers/lightnvm/pblk-recovery.c, 976:
> 	spin_lock in pblk_recov_l2p
> 
> [FUNC] bio_map_kern(GFP_KERNEL)
> drivers/lightnvm/pblk-core.c, 762:
> 	bio_map_kern in pblk_line_submit_smeta_io
> drivers/lightnvm/pblk-core.c, 1048:
> 	pblk_line_submit_smeta_io in pblk_line_init_bb
> drivers/lightnvm/pblk-core.c, 1434:
> 	pblk_line_init_bb in pblk_line_replace_data
> drivers/lightnvm/pblk-recovery.c, 980:
> 	pblk_line_replace_data in pblk_recov_l2p
> drivers/lightnvm/pblk-recovery.c, 976:
> 	spin_lock in pblk_recov_l2p
> 
> To fix these bugs, GFP_KERNEL is replaced with GFP_ATOMIC.
> 
> These bugs are found by my static analysis tool DSAC.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> ---
>   drivers/lightnvm/pblk-core.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> index ed9cc977c8b3..5d915c93b6cf 100644
> --- a/drivers/lightnvm/pblk-core.c
> +++ b/drivers/lightnvm/pblk-core.c
> @@ -802,7 +802,7 @@ static int pblk_line_submit_smeta_io(struct pblk *pblk, struct pblk_line *line,
>   
>   	memset(&rqd, 0, sizeof(struct nvm_rq));
>   
> -	rqd.meta_list = nvm_dev_dma_alloc(dev->parent, GFP_KERNEL,
> +	rqd.meta_list = nvm_dev_dma_alloc(dev->parent, GFP_ATOMIC,
>   							&rqd.dma_meta_list);
>   	if (!rqd.meta_list)
>   		return -ENOMEM;
> @@ -810,7 +810,7 @@ static int pblk_line_submit_smeta_io(struct pblk *pblk, struct pblk_line *line,
>   	rqd.ppa_list = rqd.meta_list + pblk_dma_meta_size;
>   	rqd.dma_ppa_list = rqd.dma_meta_list + pblk_dma_meta_size;
>   
> -	bio = bio_map_kern(dev->q, line->smeta, lm->smeta_len, GFP_KERNEL);
> +	bio = bio_map_kern(dev->q, line->smeta, lm->smeta_len, GFP_ATOMIC);
>   	if (IS_ERR(bio)) {
>   		ret = PTR_ERR(bio);
>   		goto free_ppa_list;
> 

Javier,

What do you think? I'm OK with applying this, but one could also move 
the allocs outside the spinlocks?

-Matias