From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 94095C4451B for ; Fri, 17 Jul 2026 17:27:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 88C5C6B00CB; Fri, 17 Jul 2026 13:27:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 864146B00CC; Fri, 17 Jul 2026 13:27:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 77A706B00CD; Fri, 17 Jul 2026 13:27:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 3AF166B00CB for ; Fri, 17 Jul 2026 13:27:46 -0400 (EDT) Received: from smtpin29.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id ADB7F8014F for ; Fri, 17 Jul 2026 17:27:45 +0000 (UTC) X-FDA: 84998950890.29.E0753BA Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf11.hostedemail.com (Postfix) with ESMTP id 0D2EB4000C for ; Fri, 17 Jul 2026 17:27:43 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=L87zM+vX; spf=pass (imf11.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784309264; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6pQm/Ojh5C3HMOQwR66ivQbCKfkvu5WSMILH5D2c3DA=; b=mAvUtzeLWPD1p8hZuHGKF3N49rMr5qjGB+plH7fm/WgWMt7adVPONEQhETqG7bHgQ3EoNd 1IAJYNnN5vgr2CqKBnAovJUm3uQi/dub4TGi7a/c+DHmymxIYZZpDYGH+fKotAzBg+NHvn nE15ERbnIil47f+6M+WQNV8O6Hx23Jk= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=L87zM+vX; spf=pass (imf11.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784309264; b=Txk7A6dXFViW5tnBKzi7fBCNMGrNIJRb9WRXIaCMEK7zoGL9KsnES+xo2bXJ8NHNdvn3DF VRepOB3zM5/KBPjUjFsR4syVQ+SZgH3qtGstt20S8oVhQ16kgkONJXsPNFvkzyVU5Ws20P lZ/zwx/lDIepcqvjsM+kPWy6+7Th57E= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 9F04760A6D; Fri, 17 Jul 2026 17:27:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE5F21F00A3D; Fri, 17 Jul 2026 17:27:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784309263; bh=6pQm/Ojh5C3HMOQwR66ivQbCKfkvu5WSMILH5D2c3DA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=L87zM+vX3nYW7/x31SZ8P1ixK6XcMEKB+Lfgk3QLsMu4NHWMKlAFtv7FCyDtW4WFk SUXf75Saw0cu/nF94tgqw+ytukguPjC/QRj0rrCiD54C+07h5RSWQGj4g+cUmpYSwA ZOriBrDMr3pEI4dc1fubJ4nW71n1+MoSgyor5yJ64XQbIt6LqtzH//tuVcl0QH6O3W Wjw24fXun3+j3jZOnO/mjVq3S4oMqCU9Tj/2HgRbhF2C2rOJeZheVCexT9JOrTx9fT 1CNdEAJ40J3NhAjwYYn5kppvkK/SxsY8sGlBh+VVt6Phkn+X/p70dWY2kozf2/B4WR OT3JHT/z826Iw== From: "Lorenzo Stoakes (ARM)" Date: Fri, 17 Jul 2026 18:27:11 +0100 Subject: [PATCH v2 3/3] mm/mseal: remove further superfluous comments, do_mseal() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260717-mseal-fixups-v2-3-0daa0014b813@kernel.org> References: <20260717-mseal-fixups-v2-0-0daa0014b813@kernel.org> In-Reply-To: <20260717-mseal-fixups-v2-0-0daa0014b813@kernel.org> To: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=4363; i=ljs@kernel.org; h=from:subject:message-id; bh=MDOTli1ONneEZj3m3sNVoalGk6wNclirN2tJYNxD1yY=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKiUr+86nw2y1b1D+esnC0ORWVN159smf6hsWfnPH+tR Yc8a4tfd5SyMIhxMciKKbI8/yK+P0gkbF7nBX83mDmsTCBDGLg4BWAiN94x/DN7nrwvm3ulVDBb 53PW7wECgSy2Ey5tXWRzVCOmu6tVl42R4c33DseQqdfFa5mSr/nVXrm28l7z3ZB5L348Tlq28OY Hbg4A X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0D2EB4000C X-Stat-Signature: ysufo1pdrrwg6nbm5i47akya5mxq93ak X-HE-Tag: 1784309263-716619 X-HE-Meta: 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 0IBrbDHp iygvNN0FLoanrTWgA6l7C/E+XdKL5Tt6Rdj7jevl3Acd1HggD2fbQ2LyC7JFoDcIqSsY21OuCdudkjDE1OqTzXq77U8uWJVjao+5UfhNqiErMnkqWzIyubXhnlpwqkxG1Yubf7hbUaqnaCW6nHUKOZjNBBpwLXzXIovEFyJOYlfL76meqSg40uRJTM6A3FbUbYT0a8yeGDP3x0V0nS8dR7dXB1JKkkJD3a/YdjYHnLZx/7Y/lHXTSB14mGavkWEzthJjw77SdNErEpZ6J6rl3wiKIcL/Cst29ZvWV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: There's no need to abstract do_mseal() any longer so put the system call implementation in the system call declaration. The comment around do_mseal() is strangely formatted, overly long and adds a lot of superfluous information that the code already provides, so boil it down to the essentials. Acked-by: David Hildenbrand (Arm) Reviewed-by: Pedro Falcato Signed-off-by: Lorenzo Stoakes (ARM) --- mm/mseal.c | 74 ++++++++++++++------------------------------------------------ 1 file changed, 16 insertions(+), 58 deletions(-) diff --git a/mm/mseal.c b/mm/mseal.c index 2a516da694c6..7a8ac66dc215 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -99,61 +99,25 @@ void mseal_mmap_page_zero(void) } /* - * mseal(2) seals the VM's meta data from - * selected syscalls. + * Seal VMAs in the specified input range to prevent an attacker replacing what + * is mapped in the range with something else. * - * addr/len: VM address range. + * Disallows: + * - VMA unmapping, remapping or shrinking. + * - Overwriting the VMA with another one via mmap(), mremap() or similar. + * - Alteration of properties via mprotect()/pkey_mprotect(). + * - Destructive madvise() behaviours (like MADV_DONTNEED) on anonymous read-only + * ranges. * - * The address range by addr/len must meet: - * start (addr) must be in a valid VMA. - * end (addr + len) must be in a valid VMA. - * no gap (unallocated memory) between start and end. - * start (addr) must be page aligned. + * Since unmapped ranges can be mapped at any time, the input range must span + * mapped ranges only. * - * len: len will be page aligned implicitly. - * - * Below VMA operations are blocked after sealing. - * 1> Unmapping, moving to another location, and shrinking - * the size, via munmap() and mremap(), can leave an empty - * space, therefore can be replaced with a VMA with a new - * set of attributes. - * 2> Moving or expanding a different vma into the current location, - * via mremap(). - * 3> Modifying a VMA via mmap(MAP_FIXED). - * 4> Size expansion, via mremap(), does not appear to pose any - * specific risks to sealed VMAs. It is included anyway because - * the use case is unclear. In any case, users can rely on - * merging to expand a sealed VMA. - * 5> mprotect and pkey_mprotect. - * 6> Some destructive madvice() behavior (e.g. MADV_DONTNEED) - * for anonymous memory, when users don't have write permission to the - * memory. Those behaviors can alter region contents by discarding pages, - * effectively a memset(0) for anonymous memory. - * - * flags: reserved. - * - * return values: - * zero: success. - * -EINVAL: - * invalid input flags. - * start address is not page aligned. - * Address range (start + len) overflow. - * -ENOMEM: - * addr is not a valid address (not allocated). - * end (start + len) is not a valid address. - * a gap (unallocated memory) between start and end. - * -EPERM: - * - In 32 bit architecture, sealing is not supported. - * Note: - * user can call mseal(2) multiple times, adding a seal on an - * already sealed memory is a no-action (no error). - * - * unseal() is not supported. + * The flags parameter is currently reserved. */ -static int do_mseal(unsigned long start, size_t len_in, unsigned long flags) +SYSCALL_DEFINE3(mseal, unsigned long, start, size_t, len, unsigned long, flags) { + size_t len_aligned; unsigned long end; - size_t len; /* Verify flags not set. */ if (flags) @@ -163,12 +127,12 @@ static int do_mseal(unsigned long start, size_t len_in, unsigned long flags) if (!PAGE_ALIGNED(start)) return -EINVAL; - len = PAGE_ALIGN(len_in); + len_aligned = PAGE_ALIGN(len); /* Check to see whether len was rounded up from small -ve to zero. */ - if (len_in && !len) + if (len && !len_aligned) return -EINVAL; - end = start + len; + end = start + len_aligned; if (end < start) return -EINVAL; @@ -177,9 +141,3 @@ static int do_mseal(unsigned long start, size_t len_in, unsigned long flags) return mseal_range(start, end); } - -SYSCALL_DEFINE3(mseal, unsigned long, start, size_t, len, unsigned long, - flags) -{ - return do_mseal(start, len, flags); -} -- 2.55.0