linux-kernel - Re: [PATCH V2] lightnvm: protect target type list with correct locks

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Message-Id: <3891AF6A-D87D-4727-BF9C-E6689C232BC9@lightnvm.io>
Date:   Mon, 18 Sep 2017 09:53:43 +0200
From:   Javier González <jg@...htnvm.io>
To:     Rakesh Pandit <rakesh@...era.com>
Cc:     Matias Bjørling <mb@...htnvm.io>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] lightnvm: protect target type list with correct locks

> On 16 Sep 2017, at 20.39, Rakesh Pandit <rakesh@...era.com> wrote:
> 
> nvm_tgt_types list was protected by wrong lock for NVM_INFO ioctl call
> and can race with addition or removal of target types.  Also
> unregistering target type was not protected correctly.
> 
> Fixes: 5cd907853 ("lightnvm: remove nested lock conflict with mm")
> Signed-off-by: Rakesh Pandit <rakesh@...era.com>
> ---
> 
> V2: also add correct lock while unregistering and fix "Fixes" tag at
> end.  Note I found these while investigating another issue and
> skimming the core code but worth fixing.
> 
> drivers/lightnvm/core.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
> index 9f9a137..1b8338d 100644
> --- a/drivers/lightnvm/core.c
> +++ b/drivers/lightnvm/core.c
> @@ -589,9 +589,9 @@ void nvm_unregister_tgt_type(struct nvm_tgt_type *tt)
> 	if (!tt)
> 		return;
> 
> -	down_write(&nvm_lock);
> +	down_write(&nvm_tgtt_lock);
> 	list_del(&tt->list);
> -	up_write(&nvm_lock);
> +	up_write(&nvm_tgtt_lock);
> }
> EXPORT_SYMBOL(nvm_unregister_tgt_type);
> 
> @@ -1190,7 +1190,7 @@ static long nvm_ioctl_info(struct file *file, void __user *arg)
> 	info->version[1] = NVM_VERSION_MINOR;
> 	info->version[2] = NVM_VERSION_PATCH;
> 
> -	down_write(&nvm_lock);
> +	down_write(&nvm_tgtt_lock);
> 	list_for_each_entry(tt, &nvm_tgt_types, list) {
> 		struct nvm_ioctl_info_tgt *tgt = &info->tgts[tgt_iter];
> 
> @@ -1203,7 +1203,7 @@ static long nvm_ioctl_info(struct file *file, void __user *arg)
> 	}
> 
> 	info->tgtsize = tgt_iter;
> -	up_write(&nvm_lock);
> +	up_write(&nvm_tgtt_lock);
> 
> 	if (copy_to_user(arg, info, sizeof(struct nvm_ioctl_info))) {
> 		kfree(info);
> --
> 2.7.4

LGTM.

Reviewed-by: Javier González <javier@...xlabs.com>


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