From nobody Tue Nov 26 18:42:04 2024 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 037C21BF37 for ; Thu, 17 Oct 2024 00:51:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.43 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729126277; cv=none; b=bY12jjNVXV1r5AyfbGW1PB0dGboPrp70uNLeedcLzFHmGWR4ubovIrMRcXdzEPYyJ+4ix1L+528eEMRnMr5SPT+4fP3jLDE8pJaEl1HlBU+PgS2h0fhnxES+Xtr+oMc/s0Hw8MBBNK9CNEXWZEA4Es9xky229KmS/U1+ITEcxtQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729126277; c=relaxed/simple; bh=IxD+p5GKEBnqW9bnHP0WW6feXUZp/DU4SEQgGZ6gu7E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u5RAKCELGkJt6yUr/dn0ILZPS/LX9jPzwZKH3jOmiJGxqXjKkDSxR+x4bUWygU/v1qtsDnnxl328YoNavmksKfEMaZTDzpiMDkWAtaHnqhGpgSuivKRAPXwASj8FFVKZ/lLJTfxiDrCvodyEUj/w5fDo0KmLxCgY+xqFl7e0Uak= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=YmcQoIeM; arc=none smtp.client-ip=209.85.216.43 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="YmcQoIeM" Received: by mail-pj1-f43.google.com with SMTP id 98e67ed59e1d1-2e3c0d1ccc6so44434a91.3 for ; Wed, 16 Oct 2024 17:51:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1729126272; x=1729731072; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=qjKlw80hPOriNww9p0Da79oYC5cYurJRNqRcXEepGpg=; b=YmcQoIeMX4SB/eIIlH/U0Do61TzJ88np1flWOZqqF7z1iMdH6pF+EV9EogNJt+duHF rhr391nLukQ429h3dIysyitz0bbXnIovwknBf+5/vHQmIvxFblbuMlvJYFUiMr//hYP1 jlsQgSX2g61csAxjUR/xhmSGD9k9fSPg+KB5k= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1729126272; x=1729731072; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=qjKlw80hPOriNww9p0Da79oYC5cYurJRNqRcXEepGpg=; b=uoItH7X+079OmaBiGAKfh8kZY4FlA1RcTZxz7ps37cTufxHaLhy37gHO0nGw3AdSNH 8wLIkU7ZlNWt2Ub295s2V60ohJUjy+K79wDoEgtTVN7gBvddfAn63b0llTlyZ2O9SutV Zfd42c3VLkLbrIxdUOtpYtYku1XyMvypICwHdQQ4jtzz7CU1c2p9LIj8SGv99+/aEjRE ovFUlWVK1C/N7Nx/40J75MK8oRYgdLjSgFpPNbhEcWyMuJvoBqBvONKBkeNtfi3lmIj+ GAVNE/NcGU7NMPPr3fUHCO/HlQtkyopqo5OkT49jg2XgxF7dy3h48AY5pVS1tiTOYgig PLtQ== X-Forwarded-Encrypted: i=1; AJvYcCXkyzSNz2vGtxUKBk3imgaQ0gdXq4CwW8dPD+hWmAMGLxSRiEcPbJ66MJ0rj8e1sgnsxufYi4ol8uiULUM=@vger.kernel.org X-Gm-Message-State: AOJu0Ywo8OCNhQYbcMOZWCjJi7pBdn3F7TJbHQz6PPnHx99R+jGlujrD Fp3Sz5TdjDeJ08jP26jbWBIcSvtTdzeqsqw4LcN9rhvKtqsQvWynY2/8yM+MWQ== X-Google-Smtp-Source: AGHT+IG+nZEmIFxEMebL8zJk/ulSdARWGAMWNOvXhzs7CcDij4L3o5BGAmBhyFvsZhnXUwj/YuMYiQ== X-Received: by 2002:a17:903:32c4:b0:205:723f:23d4 with SMTP id d9443c01a7336-20d47e69b07mr7460455ad.5.1729126270776; Wed, 16 Oct 2024 17:51:10 -0700 (PDT) Received: from localhost (56.4.82.34.bc.googleusercontent.com. [34.82.4.56]) by smtp.gmail.com with UTF8SMTPSA id d9443c01a7336-20d1804c050sm34102105ad.216.2024.10.16.17.51.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Oct 2024 17:51:10 -0700 (PDT) From: jeffxu@chromium.org To: akpm@linux-foundation.org, keescook@chromium.org, torvalds@linux-foundation.org, usama.anjum@collabora.com, corbet@lwn.net, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com Cc: jeffxu@google.com, jorgelo@chromium.org, groeck@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, jannh@google.com, sroettger@google.com, pedro.falcato@gmail.com, linux-hardening@vger.kernel.org, willy@infradead.org, gregkh@linuxfoundation.org, deraadt@openbsd.org, surenb@google.com, merimus@google.com, rdunlap@infradead.org, Jeff Xu , stable@vger.kernel.org Subject: [PATCH v1 1/2] mseal: Two fixes for madvise(MADV_DONTNEED) when sealed Date: Thu, 17 Oct 2024 00:51:04 +0000 Message-ID: <20241017005105.3047458-2-jeffxu@chromium.org> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog In-Reply-To: <20241017005105.3047458-1-jeffxu@chromium.org> References: <20241017005105.3047458-1-jeffxu@chromium.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jeff Xu Two fixes for madvise(MADV_DONTNEED) when sealed. For PROT_NONE mappings, the previous blocking of madvise(MADV_DONTNEED) is unnecessary. As PROT_NONE already prohibits memory access, madvise(MADV_DONTNEED) should be allowed to proceed in order to free the page. For file-backed, private, read-only memory mappings, we previously did not block the madvise(MADV_DONTNEED). This was based on the assumption that the memory's content, being file-backed, could be retrieved from the file if accessed again. However, this assumption failed to consider scenarios where a mapping is initially created as read-write, modified, and subsequently changed to read-only. The newly introduced VM_WASWRITE flag addresses this oversight. Reported-by: Pedro Falcato Link:https://lore.kernel.org/all/CABi2SkW2XzuZ2-TunWOVzTEX1qc29LhjfNQ3hD4Ny= m8U-_f+ug@mail.gmail.com/ Fixes: 8be7258aad44 ("mseal: add mseal syscall") Cc: # 6.11.y: 4d1b3416659b: mm: move can_modify_vm= a to mm/vma.h Cc: # 6.11.y: 4a2dd02b0916: mm/mprotect: replace c= an_modify_mm with can_modify_vma Cc: # 6.11.y: 23c57d1fa2b9: mseal: replace can_mod= ify_mm_madv with a vma variant Cc: # 6.11.y Signed-off-by: Jeff Xu --- include/linux/mm.h | 2 ++ mm/mprotect.c | 3 +++ mm/mseal.c | 42 ++++++++++++++++++++++++++++++++++++------ 3 files changed, 41 insertions(+), 6 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 4c32003c8404..b402eca2565a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -430,6 +430,8 @@ extern unsigned int kobjsize(const void *objp); #ifdef CONFIG_64BIT /* VM is sealed, in vm_flags */ #define VM_SEALED _BITUL(63) +/* VM was writable */ +#define VM_WASWRITE _BITUL(62) #endif =20 /* Bits set in the VMA until the stack is in its final location */ diff --git a/mm/mprotect.c b/mm/mprotect.c index 0c5d6d06107d..6397135ca526 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -821,6 +821,9 @@ static int do_mprotect_pkey(unsigned long start, size_t= len, break; } =20 + if ((vma->vm_flags & VM_WRITE) && !(newflags & VM_WRITE)) + newflags |=3D VM_WASWRITE; + error =3D security_file_mprotect(vma, reqprot, prot); if (error) break; diff --git a/mm/mseal.c b/mm/mseal.c index ece977bd21e1..28f28487be17 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -36,12 +36,8 @@ static bool is_madv_discard(int behavior) return false; } =20 -static bool is_ro_anon(struct vm_area_struct *vma) +static bool anon_is_ro(struct vm_area_struct *vma) { - /* check anonymous mapping. */ - if (vma->vm_file || vma->vm_flags & VM_SHARED) - return false; - /* * check for non-writable: * PROT=3DRO or PKRU is not writeable. @@ -53,6 +49,22 @@ static bool is_ro_anon(struct vm_area_struct *vma) return false; } =20 +static bool vma_is_prot_none(struct vm_area_struct *vma) +{ + if ((vma->vm_flags & VM_ACCESS_FLAGS) =3D=3D VM_NONE) + return true; + + return false; +} + +static bool vma_was_writable_turn_readonly(struct vm_area_struct *vma) +{ + if (!(vma->vm_flags & VM_WRITE) && vma->vm_flags & VM_WASWRITE) + return true; + + return false; +} + /* * Check if a vma is allowed to be modified by madvise. */ @@ -61,7 +73,25 @@ bool can_modify_vma_madv(struct vm_area_struct *vma, int= behavior) if (!is_madv_discard(behavior)) return true; =20 - if (unlikely(!can_modify_vma(vma) && is_ro_anon(vma))) + /* not sealed */ + if (likely(can_modify_vma(vma))) + return true; + + /* PROT_NONE mapping */ + if (vma_is_prot_none(vma)) + return true; + + /* file-backed private mapping */ + if (vma->vm_file) { + /* read-only but was writeable */ + if (vma_was_writable_turn_readonly(vma)) + return false; + + return true; + } + + /* anonymous mapping is read-only */ + if (anon_is_ro(vma)) return false; =20 /* Allow by default. */ --=20 2.47.0.rc1.288.g06298d1525-goog