From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Thu, 01 Feb 2024 11:43:25 +0100 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1rVUXU-00FUIY-0m for lore@lore.pengutronix.de; Thu, 01 Feb 2024 11:43:25 +0100 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1rVUXU-0002Jz-4M for lore@pengutronix.de; Thu, 01 Feb 2024 11:43:25 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Cc:Content-ID:Content-Description:Resent-Date:Resent-From :Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=lncbtHrVLkaGGQnnFQGFOBTCHLNHHbYZFQu8KMH40fc=; b=K9qK5gO6mAOXX3Kf2ztBfJ2slP ujlbpSrtLrSO430gkK7svuJORmZJW0Yo3DyCmMicMJrmirKOJXd9RNluKkA68FBwUyjQYkNcbVEW2 befsjKqx1azFzfcucAhH/0XKdAICG8ExwLQPNtu7gB6QpYX8jiI0vuLMnFr1JjIU5QK0OWDf2HYQI 5WFHMDNWnGEsM0ZM1DsfG0v1jseaJ29Qxl/5FklOiCAb5oKzWNfG/b5fzZXmLigCKg2W2Ttzdg+/l 2c/9vhIoGMZUTmuGG2ZWevFDtNJhCuHRoovNwlUeVou0wiAvt6xgDQ6A3GVa7oz4jVP0glYG8wsLQ sO85aRFQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVUWz-00000007VAC-2apC; Thu, 01 Feb 2024 10:42:53 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rVUWw-00000007V9f-2O8j for barebox@lists.infradead.org; Thu, 01 Feb 2024 10:42:51 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1rVUWv-0002H5-7H; Thu, 01 Feb 2024 11:42:49 +0100 Message-ID: Date: Thu, 1 Feb 2024 11:42:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: Stefan Kerkmann , Sascha Hauer , BAREBOX References: <20240131-fix-fdt-memory-safety-v1-0-3d3a2c797eec@pengutronix.de> <20240131-fix-fdt-memory-safety-v1-2-3d3a2c797eec@pengutronix.de> <53ab0b01-2de6-4255-913e-963d921737b5@pengutronix.de> From: Ahmad Fatoum In-Reply-To: <53ab0b01-2de6-4255-913e-963d921737b5@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240201_024250_631067_B5C334C7 X-CRM114-Status: GOOD ( 20.76 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.7 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 2/2] of: fdt: fix oob writes with large ftd properties X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) On 01.02.24 11:24, Stefan Kerkmann wrote: > Hello Ahmad, > > On 31.01.24 18:21, Ahmad Fatoum wrote: >> On 31.01.24 17:57, Stefan Kerkmann wrote: >>> OOB writes can be triggered when fdt->dt_size * 2 is still smaller than >>> the property for which memory should be allocated. This can happen under >>> rare circumstances when editing a fdt with the of_property command and a >>> property is larger than 128k in size. >>> >>> This happend when editing a FIT image (which is a ftd) with the >>> of_property command and the Kernel image was around 8M in size. >>> >>> The simplified call chain is the following: >>> >>> of_property -> of_flatten_dtb -> create new fdt with 64k in size (this is >>> fixed) -> __of_flatten_dtb -> attempt to copy kernel image (8M) -> >>> fdt_ensure_space -> allocate only 128k for fdt->dt -> memcopy 8M into fdt->dt >>> buffer -> crash >>> >>> The fix is to grow fdt->dt to hold at least the new property. The power >>> of 2 increment is untouched to keep the same behaviour otherwise. >>> >>> Signed-off-by: Stefan Kerkmann >>> --- >>>   drivers/of/fdt.c | 4 ++++ >>>   1 file changed, 4 insertions(+) >>> >>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c >>> index 4f79a6120f..1f24ed0bbc 100644 >>> --- a/drivers/of/fdt.c >>> +++ b/drivers/of/fdt.c >>> @@ -399,6 +399,10 @@ static int fdt_ensure_space(struct fdt *fdt, int dtsize) >>>           previous = fdt->dt; >>>           new_size = fdt->dt_size * 2; >>>   +        while (new_size <= dtsize) { >>> +            new_size *= 2; >>> +        } >> >> A nitpick that I solely note because I already had feedback on the first patch: >> Kernel coding style is to omit { braces } for single statement blocks. >> >> In your case you could just do: >> >>   if (new_size <= dtsize) >>       new_size = roundup_pow_of_two(new_size + dtsize); >> >> I think to skip the loop. >> > > Thanks! That is the better solution. > > To not over provision memory I changed the new size to be `roundup_pow_of_two(fdt->dt_size + dtsize)` as we know for sure that `dtsize` is already larger than `fdt->dt_size * 2`. > > In (made up) case that we already have 8k space for the fdt and got a 17k property we would allocate 65k (8k + 8k + 17k = 33k ⇾ rounded ⇾ 65k) and only 32k (8k + 17k = 25k → rounded → 32k) with `fdt->dt_size + dtsize`. Sounds good. > >> Cheers, >> Ahmad >> >>> + >>>           if ((fdt->dt = memalign_realloc(previous, fdt->dt_size, >>>                           new_size)) == NULL) { >>>               free(previous); >>> >> > > Cheers > Stefan > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |