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 62AB81662E8; Thu, 29 Aug 2024 10:02:50 +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=1724925770; cv=none; b=K9WRydHwwf+TvPLliCQMdKfO78KruF2EGZcGANJgTrXu+mHhmMqrhJqRroSNr0i6PLXBxbD5v35Zb8j+6WrugrqK4+1DzV5GOv8GcxdbOaR4HWa5YvYWEhWc8cWwM4pZvi/sq/zpbrtETmJVFcqaVmBAGWNs1kK4BoJGUf/TCyA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724925770; c=relaxed/simple; bh=X8yoObr5ihzXTpuD3v0EL6+teNtYUyoMXFXQa20SoH0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BnwKmDTO+itD/JZnPh4o+hfYURAgrL+kxwB4kl6YSolEAbYzYvZV0cuwT0WP20IwQ7wTJO7e9q2CK2OxfGeCiLOzrtMYfWQYSCo34m4Qtcdo50HHh0I7UqI8If216b/Va7qVT7gsc61NlmPfSCNaLpnWo0Pni+noa4LjQup6xu0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fMIOfzR5; 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="fMIOfzR5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1917CC4CEC8; Thu, 29 Aug 2024 10:02:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724925769; bh=X8yoObr5ihzXTpuD3v0EL6+teNtYUyoMXFXQa20SoH0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fMIOfzR5jBJ9TCHHLdJMZcZkhaTVFZwgkizmlWU/T/ab3SNQyLLwwrNDlSuv9iGrW F5PBq0xTvSElpjIEXSi7Zo9ow5V2sVazrirPGJ7niI680FzkNCTCP5HBpwu3Noe/aD sz/Dxa4kCpHat3UEVw6sbUS8yquRFH2DvT8hny25dI+0DwjacKEXFBDr7skECeSdBC rfpLrToymsSRROAl7BE/LjGMK9qZHSZLIxVw+UH+f28C15MJdwdzaeanhN1az5gMUE /IQuJa8I179agan3x4uDNjtQUG9dgaaT91acyU8XAVSMOE5YNqgYRlYkhyX79R5IKT 43drKT7RRtnSQ== Message-ID: Date: Thu, 29 Aug 2024 12:02:43 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] nfc: pn533: Add poll mod list filling check To: Paolo Abeni , Aleksandr Mishin , Samuel Ortiz Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org References: <20240827084822.18785-1-amishin@t-argos.ru> <26d3f7cf-1fd8-48b6-97be-ba6819a2ff85@redhat.com> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/08/2024 11:34, Paolo Abeni wrote: > On 8/29/24 11:06, Krzysztof Kozlowski wrote: >> On 29/08/2024 10:26, Paolo Abeni wrote: >>> >>> >>> On 8/27/24 10:48, Aleksandr Mishin wrote: >>>> In case of im_protocols value is 1 and tm_protocols value is 0 this >>>> combination successfully passes the check >>>> 'if (!im_protocols && !tm_protocols)' in the nfc_start_poll(). >>>> But then after pn533_poll_create_mod_list() call in pn533_start_poll() >>>> poll mod list will remain empty and dev->poll_mod_count will remain 0 >>>> which lead to division by zero. >>>> >>>> Normally no im protocol has value 1 in the mask, so this combination is >>>> not expected by driver. But these protocol values actually come from >>>> userspace via Netlink interface (NFC_CMD_START_POLL operation). So a >>>> broken or malicious program may pass a message containing a "bad" >>>> combination of protocol parameter values so that dev->poll_mod_count >>>> is not incremented inside pn533_poll_create_mod_list(), thus leading >>>> to division by zero. >>>> Call trace looks like: >>>> nfc_genl_start_poll() >>>> nfc_start_poll() >>>> ->start_poll() >>>> pn533_start_poll() >>>> >>>> Add poll mod list filling check. >>>> >>>> Found by Linux Verification Center (linuxtesting.org) with SVACE. >>>> >>>> Fixes: dfccd0f58044 ("NFC: pn533: Add some polling entropy") >>>> Signed-off-by: Aleksandr Mishin >>> >>> The issue looks real to me and the proposed fix the correct one, but >>> waiting a little more for Krzysztof feedback, as he expressed concerns >>> on v1. >> >> There was one month delay between my reply and clarifications from >> Fedor, so original patch is neither in my mailbox nor in my brain. >> >> >> Acked-by: Krzysztof Kozlowski >> >> However different problem is: shouldn't as well or instead >> nfc_genl_start_poll() validate the attributes received by netlink? >> >> We just pass them directly to the drivers and several other drivers >> might not expect random stuff there. > > FTR, I had a similar thought and skimmed over other nfc drivers. I did > not see similar issues there. > > Additionally I fear that existing user-space could feed to the kernel > such random stuff and work happily because the kernel is currently > ignoring it - on other drivers. Such cases will suddenly stop working. > > I think we could/should merge the patch as-is, please LMK your thought. Yeah, the patch I already acked, can go in. I am just thinking whether we need a follow-up for core NFC code. Best regards, Krzysztof