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Message-ID: <202310090953.B7CE5CF4B@keescook>
Date: Mon, 9 Oct 2023 09:56:11 -0700
From: Kees Cook <keescook@...omium.org>
To: Ping-Ke Shih <pkshih@...ltek.com>
Cc: "kvalo@...nel.org" <kvalo@...nel.org>,
"llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
"trix@...hat.com" <trix@...hat.com>,
"nathan@...nel.org" <nathan@...nel.org>,
"ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
"gustavoars@...nel.org" <gustavoars@...nel.org>
Subject: Re: [PATCH] wifi: rtw89: coex: Annotate struct
rtw89_btc_btf_set_slot_table with __counted_by
On Sat, Oct 07, 2023 at 01:20:43AM +0000, Ping-Ke Shih wrote:
> On Fri, 2023-10-06 at 13:17 -0700, Kees Cook wrote:
> >
> > Prepare for the coming implementation by GCC and Clang of the __counted_by
> > attribute. Flexible array members annotated with __counted_by can have
> > their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> > array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> > functions).
> >
> > As found with Coccinelle[1], add __counted_by for struct
> > rtw89_btc_btf_set_slot_table.
> >
> > Cc: Ping-Ke Shih <pkshih@...ltek.com>
> > Cc: Kalle Valo <kvalo@...nel.org>
> > Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> > Cc: linux-wireless@...r.kernel.org
> > Cc: linux-hardening@...r.kernel.org
> > Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> > drivers/net/wireless/realtek/rtw89/coex.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/wireless/realtek/rtw89/coex.c b/drivers/net/wireless/realtek/rtw89/coex.c
> > index 4ba8b3df70ae..d66a1152c3f5 100644
> > --- a/drivers/net/wireless/realtek/rtw89/coex.c
> > +++ b/drivers/net/wireless/realtek/rtw89/coex.c
> > @@ -237,7 +237,7 @@ struct rtw89_btc_btf_set_report {
> > struct rtw89_btc_btf_set_slot_table {
> > u8 fver;
> > u8 tbl_num;
> > - u8 buf[];
> > + u8 buf[] __counted_by(tbl_num);
>
> This struct isn't defined properly. It should be
>
> struct rtw89_btc_btf_set_slot_table {
> u8 fver;
> u8 tbl_num;
> struct rtw89_btc_fbtc_slot tbl[] __counted_by(tbl_num);
> } __packed;
>
> And, we should modify rtw89_btc_fw_set_slots() as well.
>
> Another struct 'rtw89_btc_btf_set_mon_reg' has similar problem.
>
> So, NACK this patch. I will prepare one or two patches for them next week.
Ah-ha; thank you!
> By the way, I have question about __counted_by(). Can I apply it to little/big-
> endian 'num'? Like
>
> struct foo {
> ...
> __le32 num;
> __le32 data[] __counted_by(num);
> }
Unfortunately not yet. I hope to see it extended in the future to allow
for arbitrary expressions. For this first step, it only handles native
sizes.
--
Kees Cook
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