From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=62.72.0.81 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794275365; b=05+oIt5d53vYoy+P1WGPCA68kqUjIT6QZ0SG2x77FeB+q3Rdsvwmd8P1GD0kHnCKKjYZ 51AkTohJh5mUcqe3K73SoOxUcgMNgp8Qd0XzzJ5Kp9xJMyaljV3FGxaoGz51MWJk3Eq57 hTat8Rj3/j0kzfToU6LT2lwHIQcr2hmuHF4afWeNF8LcbBiI9UQsickfoJTvGs6XiHFxV L6sXULTM73YGGxGoMRdzytVoPxhHi46v02E3MXe29QxGJ3Bf00iTaLna9fSeqmYkUSDYV RSuBgqMZRFnGiegrHA4kmd4Xev3nsNViOO6xzgF66KaegprC9TWE7g+dIJv6/TL/PSg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794275365; h=DMARC-Filter:DKIM-Signature:Received:Received:Date:From:To:cc: Subject:In-Reply-To:Message-ID:References:MIME-Version:Content-Type; bh=dGP3oQkxG3O8JCUGO0KxGDQL8mkVh24OfjeHZDaL43g=; b=A8uvJX20iv0QjmssCqyB3TSgOrOGjUe4xMiUR7nFgqB3IpYRG9etJHHFEytoLQVSWUl3 z8/TFRnO+A8H/uGvd4CHy77MSXm1adYgb901CXjT3TfGPt2NQ9yGKaXI6krU8ZhUwI4vp ACZGta2nUFsI65637O59Drd2xgvOw69wsAj7yERtb2sx6vU8TOmzI9H9LGbdm6voK6+eb c0TNnwXbevB8mR3XkGY2bVJ4qv7+kEFfvOFVrba73uKAZIKUpa95yZmLfa4b45s3TcrPA PMe0IN1DUB58AGsaaX+qp4OmwzLKQdd04sH/AuWKMsC9ZAYyFCOyvqTewyn3w0ZFmKg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gentwo.org; spf=pass smtp.mailfrom=gentwo.org; dkim=pass header.d=gentwo.org header.i=@gentwo.org header.a=rsa-sha256 header.s=default header.b=E3LOkK27; arc=none smtp.remote-ip=62.72.0.81 Received: from gentwo.org (gentwo.org [62.72.0.81]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 896D9606A321; Tue, 10 Nov 2026 01:49:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 896D9606A321 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=gentwo.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gentwo.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=gentwo.org header.i=@gentwo.org header.a=rsa-sha256 header.s=default header.b=E3LOkK27 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.org; s=default; t=1794275364; bh=7OfvsyWkqHG1aqQLcvzobdPCzMSRDAQfKu/eu5xKdxg=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=E3LOkK27gn5eHFSrMZGs+cczhqLC6805mjcsN8xtgdjPeEK39Tyh6Pui2Eni6eJYt er/7/IDmt3Kr2ehckzAsUPgnbhD+/0YW3U+gagGWKiNjr5GmPoeFhsPznVX/S5Mjcz RjyzV2yPPBqYqrTs13Y1J+bOw2nJxNxMd1pwXDOw= Received: by gentwo.org (Postfix, from userid 1007) id 0122F402BC; Mon, 09 Nov 2026 17:49:23 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id F29EF402AB; Mon, 09 Nov 2026 17:49:23 -0800 (PST) Date: Mon, 9 Nov 2026 17:49:23 -0800 (PST) From: Shubhang To: Andrew Morton cc: Uladzislau Rezki , Nicholas Piggin , Shubhang Kaushik , "Christoph Lameter (Ampere)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/vmalloc: reject overflowing vm_map_ram page counts In-Reply-To: <20261101201659.c6c07375429df81081ce8b0f@linux-foundation.org> Message-ID: References: <20261022-vmalloc-reject-overflow-v2-1-0db7a20c53f0@gentwo.org> <20261101201659.c6c07375429df81081ce8b0f@linux-foundation.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Hi Andrew, On Sun, 1 Nov 2026, Andrew Morton wrote: > > Is there a case where userspace can actually hit this, or is it a > theoretical case which can't actually be encountered, or something else? > Reaching vm_map_ram() with an overflowing count from userspace is real (as noted in the udmabuf path earlier), but actually hitting an oops or corruption remains theoretical because in-tree callers don't access beyond the truncated size. The changelog described what happens if a caller does access the full requested range. I can send a v3 clarifying that the failure mode is theoretical if you'd prefer. Thanks, Shubhang Kaushik