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 761F11EA6F for ; Mon, 8 Jul 2024 15:51:55 +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=1720453915; cv=none; b=Eh2i2Ndy68wZW0PNY1eYmIr58cIz7hI+QGw194XeWX4GFDqPAdddNBDA1UAV2Hz1+FDv0Fx78WjmHYbW5UhkPpQNuEBS5bsZ1O4cX7P17u610XUTnSUkAUq5sGxzG0FOCq6FVr3ppfWNCWiVNHwG+mWzMEJijLb0lTzooVm0qaA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720453915; c=relaxed/simple; bh=VGT2Ll0BJ6zWJMZY1Uv8uMUUvBNnE0W8cZ1/Ln03WAc=; h=From:To:Cc:Subject:References:Date:In-Reply-To:Message-ID: MIME-Version:Content-Type; b=gdEFZM3O63hq207bTsMX1UzgHPx2ZCxgeexOE+dZ3lo4/6hMEM9FsRglro38OcuBfIN0uakp/66oDqu/Br2NttCKABXpcFV2Sy8tYBrRSv3JlUVw2cWbv+zfGV8cHUgujlDa8VnfsxiVFSwTeBg4cMaMsvo21aL5h6jMdTkZ4gY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=G53aqs6p; 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="G53aqs6p" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A098C116B1; Mon, 8 Jul 2024 15:51:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720453915; bh=VGT2Ll0BJ6zWJMZY1Uv8uMUUvBNnE0W8cZ1/Ln03WAc=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=G53aqs6pvr+E27anDXTsc3DQ93BiQ/wQUgGNZbayBnD8ooU5VY7HB9wYDSNp3Dyxo vtviRHLFubYLrGXG5rwG2001IifslRPTGwfI8CSZlbB1TLW3+dlV/6nzHt9y/RVO3X u14+U7Ydyaj9STh8ztCxv09L7F9eSgltA7dDcHlIhXaIHQP4Hfm3JJsY76e7P2Hco9 YMzb58CNm2jsdklDwqWZoDQSNAIqDa4Fie6uja54Kp+20J/xPtr46dYZ5E0T166HQP jry23opEmjq0BOhURoApRLaDbmPtiV+orK7A436vvfGT/LAT8VHUgd3mRtIdYssREv 6Nct1iy8eMO+w== From: Kalle Valo To: Kees Cook 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() References: <20240704144341.207317-1-kvalo@kernel.org> <202407041551.1DC8C03D@keescook> Date: Mon, 08 Jul 2024 18:51:52 +0300 In-Reply-To: <202407041551.1DC8C03D@keescook> (Kees Cook's message of "Thu, 4 Jul 2024 16:25:03 -0700") Message-ID: <877cdvdgpz.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) 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-Transfer-Encoding: quoted-printable Kees Cook writes: > On Thu, Jul 04, 2024 at 05:43:41PM +0300, Kalle Valo wrote: >> From: Kalle Valo >>=20 >> Johannes reported with GCC 11.4 there's a fortify warning below. The war= ning 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. Ah, thanks for correcting. I just saw fortify-string.h and made the wrong assumption. > 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 >> =E2=80=98ath12k_wow_convert_8023_to_80211.constprop=E2=80=99: >> ./include/linux/fortify-string.h:114:33: error: =E2=80=98__builtin_memcp= y=E2=80=99 >> accessing 18446744073709551611 or more bytes at offsets 0 and 0 >> overlaps 9223372036854775799 bytes at offset -9223372036854775804 >> [-Werror=3Drestrict] > > 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/wireles= s/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 =3D eth_pkt_ofs + a1_ofs; >>=20=20 >> - 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). Earlier I did some testing and I noticed that this if test also gives a warning: 1 + eth_pat_len < ETH_ALEN But this doesn't have any warning: 0 + eth_pat_len < ETH_ALEN And I stopped my investigation there :) > Reviewed-by: Kees Cook So you think this should be applied? It's not really logical so I would prefer to avoid taking it if possible. Or should we just ignore the warning? It only happens on GCC 11 anyway. --=20 https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatc= hes