Re: [PATCH] wifi: brcmfmac: Replace 1-element arrays with flexible arrays

[Juerg Haefliger <juerg.haefliger@canonical.com>]

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On Wed, 13 Sep 2023 10:02:12 -0600
"Gustavo A. R. Silva" <gustavo@embeddedor.com> wrote:

> On 9/13/23 00:54, Juerg Haefliger wrote:
> > Since commit 2d47c6956ab3 ("ubsan: Tighten UBSAN_BOUNDS on GCC"),
> > UBSAN_BOUNDS no longer pretends 1-element arrays are unbounded. Walking
> > 'element' and 'channel_list' will trigger warnings, so make them proper
> > flexible arrays.
> > 
> > False positive warnings were:
> > 
> >    UBSAN: array-index-out-of-bounds in drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:6984:20
> >    index 1 is out of range for type '__le32 [1]'
> > 
> >    UBSAN: array-index-out-of-bounds in drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c:1126:27
> >    index 1 is out of range for type '__le16 [1]'
> > 
> > for these lines of code:
> > 
> >    6884  ch.chspec = (u16)le32_to_cpu(list->element[i]);
> > 
> >    1126  params_le->channel_list[i] = cpu_to_le16(chanspec);
> > 
> > Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
> > ---
> >   .../wireless/broadcom/brcm80211/brcmfmac/fwil_types.h    | 9 +++++++--
> >   1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h
> > index bece26741d3a..ed723a5b5d54 100644
> > --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h
> > +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h
> > @@ -442,7 +442,12 @@ struct brcmf_scan_params_v2_le {
> >   				 * fixed parameter portion is assumed, otherwise
> >   				 * ssid in the fixed portion is ignored
> >   				 */
> > -	__le16 channel_list[1];	/* list of chanspecs */
> > +	union {
> > +		__le16 padding;	/* Reserve space for at least 1 entry for abort
> > +				 * which uses an on stack brcmf_scan_params_v2_le
> > +				 */
> > +		DECLARE_FLEX_ARRAY(__le16, channel_list);	/* chanspecs */
> > +	};
> >   };
> >   
> >   struct brcmf_scan_results {
> > @@ -702,7 +707,7 @@ struct brcmf_sta_info_le {
> >   
> >   struct brcmf_chanspec_list {
> >   	__le32	count;		/* # of entries */
> > -	__le32	element[1];	/* variable length uint32 list */
> > +	DECLARE_FLEX_ARRAY(__le32, element);	/* variable length uint32 list */  
> 
> If no padding is needed, as in the other case, then DFA() is not necessary.
> Just remove the 1 from the array declaration:
> 
>   struct brcmf_chanspec_list {
>          __le32  count;          /* # of entries */
> -       __le32  element[1];     /* variable length uint32 list */
> +       __le32  element[];      /* variable length uint32 list */
>   };

Ah, I wasn't sure if that is still acceptable. Will send a v2.

...Juerg

 
> --
> Gustavo
> 
> >   };
> >   
> >   /*  


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