linux-kernel - Re: [PATCH] staging: r8188eu: Use kzalloc() with GFP

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Message-ID: <YgI40Dm/ar+IubIA@kroah.com>
Date:   Tue, 8 Feb 2022 10:33:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: r8188eu: Use kzalloc() with GFP_ATOMIC in
 atomic context

On Sun, Feb 06, 2022 at 11:59:43PM +0100, Fabio M. De Francesco wrote:
> Use the GFP_ATOMIC flag of kzalloc() with two memory allocation in
> rtw_set_key(). This function is called while holding spinlocks and with
> disabled bottom halves, therefore it is not allowed to sleep. With the
> GFP_ATOMIC type flag, the allocation is high priority and cannot sleep.
> 
> This issue is detected by Smatch which emits the following warning:
> drivers/staging/r8188eu/core/rtw_pwrctrl.c:79 ips_leave() warn: sleeping in atomic context
> drivers/staging/r8188eu/core/rtw_pwrctrl.c:81 ips_leave() warn: sleeping in atomic context
> 
> The calls chain (in reverse order) is the following:
> 
> rtw_set_key()
> -> ips_leave()
> -> -> rtw_pwr_wakeup()
> -> -> -> rtw_set_802_11_disassociate()
> 
> The disabilitation of bottom halves and the acquisition of a spinlock is in
> rtw_set_802_11_disassociate().
> 
> After the changes, the post-commit hook output the following messages:
> 
> CHECK: Prefer kzalloc(sizeof(*pcmd)...) over kzalloc(sizeof(struct cmd_obj)...)
> +       pcmd = kzalloc(sizeof(struct cmd_obj), GFP_ATOMIC);
> 
> CHECK: Prefer kzalloc(sizeof(*psetkeyparm)...) over kzalloc(sizeof(struct setkey_parm)...)
> +       psetkeyparm = kzalloc(sizeof(struct setkey_parm), GFP_ATOMIC).
> 
> According to the above "CHECK[S]", use the preferred style in the first
> kzalloc().
> 
> Fixes: 79f712ea994d ("staging: r8188eu: Remove wrappers for kalloc() and kzalloc()")
> Fixes: 15865124feed ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
>  drivers/staging/r8188eu/core/rtw_mlme.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_mlme.c b/drivers/staging/r8188eu/core/rtw_mlme.c
> index 038bddc361c3..860835e29b79 100644
> --- a/drivers/staging/r8188eu/core/rtw_mlme.c
> +++ b/drivers/staging/r8188eu/core/rtw_mlme.c
> @@ -1600,12 +1600,12 @@ int rtw_set_key(struct adapter *adapter, struct security_priv *psecuritypriv, in
>  	struct mlme_priv		*pmlmepriv = &adapter->mlmepriv;
>  	int	res = _SUCCESS;
>  
> -	pcmd = kzalloc(sizeof(struct cmd_obj), GFP_KERNEL);
> +	pcmd = kzalloc(sizeof(*pcmd), GFP_ATOMIC);
>  	if (!pcmd) {
>  		res = _FAIL;  /* try again */
>  		goto exit;
>  	}
> -	psetkeyparm = kzalloc(sizeof(struct setkey_parm), GFP_KERNEL);
> +	psetkeyparm = kzalloc(sizeof(*psetkeyparm), GFP_ATOMIC);

You are making two different changes here.  Please do the first patch to
change the sizeof() change to fix up checkpatch, and then the second one
for the GFP_ATOMIC change so that if there is a problem with either of
them we can only revert the offending change.

thanks,

greg k-h