linux-kernel - Re: [PATCH 1/2] staging: r8188eu: properly handle the kzalloc()

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Date:   Thu, 31 Mar 2022 08:03:08 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     xkernel.wang@...mail.com
Cc:     Larry.Finger@...inger.net, phil@...lpotter.co.uk,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] staging: r8188eu: properly handle the kzalloc()

On Wed, Mar 30, 2022 at 11:16:07PM +0800, xkernel.wang@...mail.com wrote:
> From: Xiaoke Wang <xkernel.wang@...mail.com>
> 
> kzalloc() is a memory allocation function which can return NULL when
> some internal memory errors happen. So it is better to handle the return
> of it to prevent potential wrong memory access.
> For the kzalloc() in go_add_group_info_attr(), since there is a lack
> of error handlers along the call chain it lies and the lifetime of
> `pdata_attr` is only in go_add_group_info_attr(), `pdata_attr` is roughly
> changed to a local variable on stack like the other functions in 
> rtw_p2p.c, such as `u8 p2pie[MAX_P2P_IE_LEN] = { 0x00 };` in 
> issue_p2p_presence_resp().
> 
> Signed-off-by: Xiaoke Wang <xkernel.wang@...mail.com>
> ---
>  drivers/staging/r8188eu/core/rtw_p2p.c     |  6 ++----
>  drivers/staging/r8188eu/core/rtw_xmit.c    | 12 +++++++++---
>  drivers/staging/r8188eu/include/rtw_xmit.h |  2 +-
>  3 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_p2p.c b/drivers/staging/r8188eu/core/rtw_p2p.c
> index e2b6cf2..f1a5df8 100644
> --- a/drivers/staging/r8188eu/core/rtw_p2p.c
> +++ b/drivers/staging/r8188eu/core/rtw_p2p.c
> @@ -27,15 +27,14 @@ static u32 go_add_group_info_attr(struct wifidirect_info *pwdinfo, u8 *pbuf)
>  	struct list_head *phead, *plist;
>  	u32 len = 0;
>  	u16 attr_len = 0;
> -	u8 tmplen, *pdata_attr, *pstart, *pcur;
> +	u8 pdata_attr[MAX_P2P_IE_LEN] = { 0x00 };

You just created a huge variable on the stack.  Are you _SURE_ that is
ok?

Have you tested this change to make sure it works?  If not, I can't take
it, sorry.

greg k-h