Re: [PATCH 3/5] staging: r8188eu: use helper to check for broadcast address

Dan Carpenter
2021-11-02T14:59:48Z

On Fri, Oct 22, 2021 at 11:21:10AM +0200, Martin Kaiser wrote:
> Thus wrote Michael Straube (straube.linux@gmail.com):
>
> > > > + !is_broadcast_ether_addr(GetAddr1Ptr(pframe)))
>
> > Hi Martin,
>
> > I'm not an expert regarding alignment. Is GetAddr1Ptr(pframe) always
> > __aligned(2) as required by is_broadcast_ether_addr?
>
> Hi Michael,
>
> thanks for spotting this. To be honest, I didn't look at this in much
> detail when I wrote the patch.
>
> I suppose the pframe comes from recvbuf2recvframe().
> precvframe = rtw_alloc_recvframe(pfree_recv_queue);
> with
> struct __queue *pfree_recv_queue = &precvpriv->free_recv_queue;
>
> This should be initialised in _rtw_init_recv_priv().
> rtw_init_queue(&precvpriv->free_recv_queue);
> ...
> precvpriv->precv_frame_buf = (u8 *)N_BYTE_ALIGMENT((size_t)(precvpriv->pallocated_frame_buf), RXFRAME_ALIGN_SZ);
> precvframe = (struct recv_frame *)precvpriv->precv_frame_buf;
> and the frames are added to the free_recv_queue.
> RXFRAME_ALIGN_SZ is 1<<8.
>
> So pframe should be 256-byte aligned.
> GetAddr1Ptr adds 4 to the start of pframe.
>
> I guess we're safe here.

Greg already applied this patch.

I'm not sure why you're looking at precvpriv->precv_frame_buf instead of
"precv_frame->rx_data"? Am I missing something? This is actually a bit
tricky for me to analyze because it gets set in two places:

drivers/staging/r8188eu/core/rtw_recv.c | recvframe_pull | (struct recv_frame)->rx_data | 0-u64max
drivers/staging/r8188eu/hal/usb_ops_linux.c | recvbuf2recvframe | (struct recv_frame)->rx_data | 0-u64max

But the fact that we're using GetAddr1Ptr() on it at all suggests that
it must be aligned and hopefully we've verified that the ->rx_data has
enough data etc... ? This code is much trickier than I like it to be.
Anyway, this patch doesn't introduce bugs that weren't present in the
original.

>
> > > > @@ -841,7 +840,7 @@ void odm_RSSIMonitorCheck(struct odm_dm_struct *pDM_Odm)
> > > > psta = pDM_Odm->pODM_StaInfo[i];
> > > > if (IS_STA_VALID(psta) &&
> > > > (psta->state & WIFI_ASOC_STATE) &&
> > > > - memcmp(psta->hwaddr, bcast_addr, ETH_ALEN) &&
> > > > + !is_broadcast_ether_addr(psta->hwaddr) &&
>
> > Perhaps we should add __aligned(2) to the hwaddr variable in struct
> > sta_info to be safe?
>
> > u8 hwaddr[ETH_ALEN] __aligned(2);
>
> Hmm, some of those arrays in other parts of the kernel have
> __aligned(2), others don't...
>
> Can anyone else give some guidance?

This array comes after a u32 and it's not packed so it's going to
__aligned(4) already.

regards,
dan carpenter