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 C457D20A5DE; Tue, 18 Mar 2025 11:55:35 +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=1742298935; cv=none; b=auIBzS9RfPhk57Cqg3uc2YlHAhx+BHBf2vQbIWxp54Ay/1ReGlFdzRmsuyHm2AI7dQDkwBYTGVOJQOCxTbjW/JmNl9QSac4z68a7TjYZlURrqHx7Fne7P3O/Zlxlafqh7yn7Je7T5EpFLvKIX/azMSJwBN779H97VCELL4y4aC0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742298935; c=relaxed/simple; bh=ZSNeIXbXvCErlYkanU3UmhF5IB8zyMBgKavggYMUR50=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=W8VWGkiR7IdFzCrDEbBo6Vg8buFLDJvdr6la1eazXcHxHhGOo54eV1VhWQiRUIVGe2MrYRiv3tI/joNcI6u6/wJyvPTSjo74NXY/2CPyIV6Le6obrzB88XLbm3rB9GC5WjYg2Q20RF4Pl3UKiNS603+mzkaK9+t+n4BGSZ9v+FA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KnKTEkOX; 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="KnKTEkOX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A2BBC4CEEF; Tue, 18 Mar 2025 11:55:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1742298935; bh=ZSNeIXbXvCErlYkanU3UmhF5IB8zyMBgKavggYMUR50=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=KnKTEkOXx7vnhgjEgeeVf6jsFrrP0DIhOKA+YSMGQ6CkI8o2kJIxaMXJUCGt0ohww MIDUGtmRsy1CF1tTIQXKwmUJUKgbBEvqUJD5W0kK5b5HePo2T6F9HVCEt1KYzxgcSf UvGS5dKYqF5/xPiabRqHGdZS2pKTOw4SAF6EuDS9M47usU1RGsdOpkN0Z6WEgPmzzm W/Aiz3mrFT05/6HeTV0LYPLvQxqFl14QHbqhhc0Xln44HFaWrL+RMTyaxzG1fmgU+P Rs0Lubvwfcfw5c4+WH5i8OMB89r3Y+NXobq16lRjeiUW2fGNeTJXYvdLMnI5qMqUyD 8/1ZWkZMpzA2w== Message-ID: <872d008e-8412-4351-a954-29ee7c7c8315@kernel.org> Date: Tue, 18 Mar 2025 12:55:29 +0100 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: [RFC PATCH] initramfs: Add size validation to prevent tmpfs exhaustion To: David Disseldorp , Stephen Eta Zhou Cc: "jsperbeck@google.com" , "akpm@linux-foundation.org" , "gregkh@linuxfoundation.org" , "lukas@wunner.de" , "wufan@linux.microsoft.com" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" References: <20250317182157.7adbc168.ddiss@suse.de> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 17/03/2025 08:21, David Disseldorp wrote: >> From 3499daeb5caf934f08a485027b5411f9ef82d6be Mon Sep 17 00:00:00 2001 >> From: Stephen Eta Zhou >> Date: Fri, 14 Mar 2025 12:32:59 +0800 >> Subject: [PATCH] initramfs: Add size validation to prevent tmpfs exhaustion >> >> When initramfs is loaded into a small memory environment, if its size >> exceeds the tmpfs max blocks limit, the loading will fail. Additionally, >> if the required blocks are close to the tmpfs max blocks boundary, >> subsequent drivers or subsystems using tmpfs may fail to initialize. >> >> To prevent this, the size limit is set to half of tmpfs max blocks. >> This ensures that initramfs can complete its mission without exhausting >> tmpfs resources, as user-space programs may also rely on tmpfs after boot. >> >> This patch adds a validation mechanism to check the decompressed size >> of initramfs based on its compression type and ratio. If the required >> blocks exceed half of the tmpfs max blocks limit, the loading will be >> aborted with an appropriate error message, exposing the issue early >> and preventing further escalation. > > This behaviour appears fragile and quite arbitrary. I don't think > initramfs should be responsible for making any of these decisions. > > Why can't the init binary make the decision of whether or not the amount > of free memory remaining is sufficient for user-space, instead of this > magic 50% limit? > > What are you trying to achieve by failing in this way before initramfs > extraction instead of during / after? Just in case before anyone tries to actually apply it: the entire patch has both corrupted header and actual patch is corrupted - all indentation messed. Best regards, Krzysztof