From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF274143748 for ; Thu, 4 Jul 2024 23:25:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720135504; cv=none; b=d9itMUECDkWldLbaDGznMUgZn+1I1NawAOFg1T+n23fMJxQ/tht6J99zAZZGgtKBeo8NL15RdQTDNg4Btgj7X2ylTN2su1c3K99zg9RLKXazKVp0N2ZLtVdo14fTRKPvu+R7bI6TxJW8ofBEPlaYe9lnOGirCIya9OCSLsS3TWE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720135504; c=relaxed/simple; bh=h/MhLT48xCMPodi/QfEIU2H8ZaCUdDmFDJhZGxscQw0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KhxrAyH+QW9X36pzN3B0yHSGqayHw/kUqgFho6lg5//TE1dco//EbbGj6zYOM/dkbVD3QD3O9P+6zDDQXK1ZA6SlbNHGafMDaVFIAOh9F7uJrifrdrn+8dGfwgZCV6IZyoDhCRnwZjYV7VBk3wqHCcxa57PldkC+6z+yNa3RAw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mMY9OE+Y; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mMY9OE+Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62D23C3277B; Thu, 4 Jul 2024 23:25:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720135504; bh=h/MhLT48xCMPodi/QfEIU2H8ZaCUdDmFDJhZGxscQw0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mMY9OE+YBKmII3oiZLlmhKJuwEya5BjSfhAMfeQoUj9UzeanyfjO0yQcrc7dxSCl2 6hKiPb/dS/dVWO8vcxHPguE4i6N/DCMni7SfThs4k6P3qy37woRZVl9wAsOvSeE5rJ p5zuwut+XosjVlrYQLNcOJpNKD7zxnfHg5ikOe0UPIIrIxVDDO9Cl4/tI745nxGAe0 HDw/Xwv14HrWbEAWku7HKZJ5J6mS41QtSMJL2cxrrcwVIOGS/bob0frJXrKIB3+KD9 sGlJxiOCTcQs9tdVXzkrmQJIid7CE4bEibxeVoJLe/ff5ORFwa7php5N/WriA8umZ9 y+VHa+xIVvvDA== Date: Thu, 4 Jul 2024 16:25:03 -0700 From: Kees Cook To: Kalle Valo Cc: ath12k@lists.infradead.org, linux-wireless@vger.kernel.org Subject: Re: [PATCH RFC] wifi: ath12k: workaround fortify warnings in ath12k_wow_convert_8023_to_80211() Message-ID: <202407041551.1DC8C03D@keescook> References: <20240704144341.207317-1-kvalo@kernel.org> Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240704144341.207317-1-kvalo@kernel.org> On Thu, Jul 04, 2024 at 05:43:41PM +0300, Kalle Valo wrote: > From: Kalle Valo > > Johannes reported with GCC 11.4 there's a fortify warning below. The warning is > not seen with GCC 12.1 nor 13.2. Weirdly moving the other operand of sum to the > other side the warning goes away. This is safe to do as the value of the > operand is check earlier. But the code looks worse with this so I'm not sure > what to do. FWIW, this isn't fortify, but -Wrestrict. I would expect the same warnings even with CONFIG_FORTIFY_SOURCE disabled. Regardless, it's worth figuring out what's going on. It looks like this is GCC's value range tracker deciding it sees a way for things to go weird. I suspect they fixed -Wrestrict in later GCC versions. It might need to be version-limited... > In file included from ./include/linux/string.h:374, > from ./include/linux/bitmap.h:13, > from ./include/linux/cpumask.h:13, > from ./include/linux/sched.h:16, > from ./include/linux/delay.h:23, > from drivers/net/wireless/ath/ath12k/wow.c:7: > drivers/net/wireless/ath/ath12k/wow.c: In function ‘ath12k_wow_convert_8023_to_80211.constprop’: > ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ accessing 18446744073709551611 or more bytes at offsets 0 and 0 overlaps 9223372036854775799 bytes at offset -9223372036854775804 [-Werror=restrict] These huge negative values imply to me that GCC is looking at some signed values somewhere. > [...] > diff --git a/drivers/net/wireless/ath/ath12k/wow.c b/drivers/net/wireless/ath/ath12k/wow.c > index c5cba825a84a..e9588bb7561c 100644 > --- a/drivers/net/wireless/ath/ath12k/wow.c > +++ b/drivers/net/wireless/ath/ath12k/wow.c > @@ -186,7 +186,7 @@ ath12k_wow_convert_8023_to_80211(struct ath12k *ar, > if (eth_pkt_ofs < ETH_ALEN) { > pkt_ofs = eth_pkt_ofs + a1_ofs; > > - if (eth_pkt_ofs + eth_pat_len < ETH_ALEN) { > + if (eth_pat_len < ETH_ALEN - eth_pkt_ofs) { > memcpy(pat, eth_pat, eth_pat_len); > memcpy(bytemask, eth_bytemask, eth_pat_len); Both eth_pkt_ofs and eth_pat_len are size_t. ETH_ALEN isn't, but it would be promoted to size_t here. The value tracker should see that eth_pkt_ofs could be [0..ETH_ALEN). eth_pat_len is coming from an "int", though, so that might be the confusion. It may think eth_pat_len could be [0..UINT_MAX] (i.e. the full range of int within size_t). So [0..ETH_ALEN) + [0..UINT_MAX] < 6 might be doing something wrong in GCC 11.x, and it's not actually doing the size_t promotion correctly, or deciding something has wrapped and then thinking eth_pat_len could span a giant region of the address space, which freaks out -Wrestrict. i.e. it's seeing that for the "if" to be true, eth_pat_len could be large enough to wrap around the addition (though this shouldn't be possible for 64-bit size_t). So I could see how [0..UINT_MAX] < 6 - [0..ETH_ALEN) would make it happier: the right side is now [1..6], so eth_pat_len becomes [1..6). Reviewed-by: Kees Cook -- Kees Cook