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[86.156.84.164]) by smtp.googlemail.com with ESMTPSA id u17-20020a05600c19d100b003dd1bd0b915sm20731309wmq.22.2023.04.03.15.28.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Apr 2023 15:28:41 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Matthew Wilcox , Mike Kravetz , Muchun Song , Alexander Viro , Christian Brauner , Andy Lutomirski , Lorenzo Stoakes Subject: [RFC PATCH 1/3] mm: drop the assumption that VM_SHARED always implies writable Date: Mon, 3 Apr 2023 23:28:30 +0100 Message-Id: <691c33e2fe8fc0fd879374739b50af48524175a3.1680560277.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: References: MIME-Version: 1.0 X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1762197348084053298?= X-GMAIL-MSGID: =?utf-8?q?1762197348084053298?= There are places in the kernel where there is an implicit assumption that VM_SHARED VMAs must either be writable or might become writable via e.g. mprotect(). We can explicitly check for the writable, shared case while remaining conservative - If VM_MAYWRITE is not set then, by definition, the memory can never be written to. Update these checks to also check for VM_MAYWRITE. Suggested-by: Andy Lutomirski Signed-off-by: Lorenzo Stoakes --- include/linux/fs.h | 4 ++-- include/linux/mm.h | 11 +++++++++++ kernel/fork.c | 2 +- mm/filemap.c | 2 +- mm/madvise.c | 2 +- mm/mmap.c | 12 ++++++------ 6 files changed, 22 insertions(+), 11 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index c85916e9f7db..373e1edd719c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -410,7 +410,7 @@ extern const struct address_space_operations empty_aops; * It is also used to block modification of page cache contents through * memory mappings. * @gfp_mask: Memory allocation flags to use for allocating pages. - * @i_mmap_writable: Number of VM_SHARED mappings. + * @i_mmap_writable: Number of VM_SHARED, VM_MAYWRITE mappings. * @nr_thps: Number of THPs in the pagecache (non-shmem only). * @i_mmap: Tree of private and shared mappings. * @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable. @@ -513,7 +513,7 @@ static inline int mapping_mapped(struct address_space *mapping) /* * Might pages of this file have been modified in userspace? - * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap + * Note that i_mmap_writable counts all VM_SHARED, VM_MAYWRITE vmas: do_mmap * marks vma as VM_SHARED if it is shared, and the file was opened for * writing i.e. vma may be mprotected writable even if now readonly. * diff --git a/include/linux/mm.h b/include/linux/mm.h index 898ece0a3802..8e64041b1703 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -862,6 +862,17 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma) return vma->vm_flags & VM_ACCESS_FLAGS; } +static inline bool is_shared_maywrite(vm_flags_t vm_flags) +{ + return (vm_flags & (VM_SHARED | VM_MAYWRITE)) == + (VM_SHARED | VM_MAYWRITE); +} + +static inline bool vma_is_shared_maywrite(struct vm_area_struct *vma) +{ + return is_shared_maywrite(vma->vm_flags); +} + static inline struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max) { diff --git a/kernel/fork.c b/kernel/fork.c index 2066a57786a8..58f257d60fee 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -733,7 +733,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, get_file(file); i_mmap_lock_write(mapping); - if (tmp->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(tmp)) mapping_allow_writable(mapping); flush_dcache_mmap_lock(mapping); /* insert tmp into the share list, just after mpnt */ diff --git a/mm/filemap.c b/mm/filemap.c index a34abfe8c654..4d896515032c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3607,7 +3607,7 @@ int generic_file_mmap(struct file *file, struct vm_area_struct *vma) */ int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma) { - if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) + if (vma_is_shared_maywrite(vma)) return -EINVAL; return generic_file_mmap(file, vma); } diff --git a/mm/madvise.c b/mm/madvise.c index 340125d08c03..606c395c4ddd 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -981,7 +981,7 @@ static long madvise_remove(struct vm_area_struct *vma, return -EINVAL; } - if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE)) + if (!vma_is_shared_maywrite(vma)) return -EACCES; offset = (loff_t)(start - vma->vm_start) diff --git a/mm/mmap.c b/mm/mmap.c index 51cd747884e3..c96dcce90772 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -106,7 +106,7 @@ void vma_set_page_prot(struct vm_area_struct *vma) static void __remove_shared_vm_struct(struct vm_area_struct *vma, struct file *file, struct address_space *mapping) { - if (vma->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(vma)) mapping_unmap_writable(mapping); flush_dcache_mmap_lock(mapping); @@ -427,7 +427,7 @@ static unsigned long count_vma_pages_range(struct mm_struct *mm, static void __vma_link_file(struct vm_area_struct *vma, struct address_space *mapping) { - if (vma->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(vma)) mapping_allow_writable(mapping); flush_dcache_mmap_lock(mapping); @@ -2596,7 +2596,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma->vm_pgoff = pgoff; if (file) { - if (vm_flags & VM_SHARED) { + if (is_shared_maywrite(vm_flags)) { error = mapping_map_writable(file->f_mapping); if (error) goto free_vma; @@ -2671,7 +2671,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma_iter_store(&vmi, vma); mm->map_count++; if (vma->vm_file) { - if (vma->vm_flags & VM_SHARED) + if (vma_is_shared_maywrite(vma)) mapping_allow_writable(vma->vm_file->f_mapping); flush_dcache_mmap_lock(vma->vm_file->f_mapping); @@ -2688,7 +2688,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, /* Once vma denies write, undo our temporary denial count */ unmap_writable: - if (file && vm_flags & VM_SHARED) + if (file && is_shared_maywrite(vm_flags)) mapping_unmap_writable(file->f_mapping); file = vma->vm_file; expanded: @@ -2734,7 +2734,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start, vma->vm_end, true); } - if (file && (vm_flags & VM_SHARED)) + if (file && is_shared_maywrite(vm_flags)) mapping_unmap_writable(file->f_mapping); free_vma: vm_area_free(vma); From patchwork Mon Apr 3 22:28:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenzo Stoakes X-Patchwork-Id: 78786 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp2630697vqo; Mon, 3 Apr 2023 15:52:04 -0700 (PDT) X-Google-Smtp-Source: AKy350Yc4TmcJLyo7NGlbQao5HYkuYI/1sIXPKYEdv8RnzLv4Cyvofbx8xJ4Q3cspckSOKOh2Co4 X-Received: by 2002:a05:6a20:c501:b0:e4:d395:5ce6 with SMTP id gm1-20020a056a20c50100b000e4d3955ce6mr271174pzb.25.1680562324305; Mon, 03 Apr 2023 15:52:04 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1680562324; cv=none; d=google.com; s=arc-20160816; b=HxMh6CMHgxJeQlJz2HBzXyvTx3kFfXfQncV3aBjvGtGs5/SPpMWEogt5V6NfMjckwz FQGIdjC+FXsO4FhPucY835zkUhwDW9z8Zie3Tt3rdp2EBuSmG0tD/UcwA1CjUJLQ1rIk xr7ymQnUJL/LCLg2J+cWF14baSDZNyUMxPaLVf5ctXTjyRoyg8kw8U3VUywqhsI/pPrL KyVnxiHDnOQaY1wkXTyeiRGzcNOpxMKL6MvpqRHQzqGDhxeGpA0d+jt/kCGBgH0VP2Op WQYDGy4DD7P4FdUdd159btdNfi2RhjYoEm/ajENDBts4+FdF7AwSW8/Ksr0Dxdy51tZY wopA== ARC-Message-Signature: i=1; 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[86.156.84.164]) by smtp.googlemail.com with ESMTPSA id u17-20020a05600c19d100b003dd1bd0b915sm20731309wmq.22.2023.04.03.15.28.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Apr 2023 15:28:43 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Matthew Wilcox , Mike Kravetz , Muchun Song , Alexander Viro , Christian Brauner , Andy Lutomirski , Lorenzo Stoakes Subject: [RFC PATCH 2/3] mm: update seal_check_[future_]write() to include F_SEAL_WRITE as well Date: Mon, 3 Apr 2023 23:28:31 +0100 Message-Id: <75478249600532faab441e43f73d4d04582efcc3.1680560277.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.40.0 In-Reply-To: References: MIME-Version: 1.0 X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1762197319870648229?= X-GMAIL-MSGID: =?utf-8?q?1762197319870648229?= Check for F_SEAL_WRITE as well for which the precise same logic can reasonably be applied, however so far this code will simply not be run as the mapping_map_writable() call occurs before shmem_mmap() or hugetlbfs_file_mmap() and thus would error out in the case of a read-only shared mapping before the logic could be applied. This therefore has no impact until the following patch which changes the order in which the *_mmap() functions are called. Signed-off-by: Lorenzo Stoakes --- fs/hugetlbfs/inode.c | 2 +- include/linux/mm.h | 13 +++++++------ mm/shmem.c | 2 +- 3 files changed, 9 insertions(+), 8 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 702d79639c0d..8ab8840707ac 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -135,7 +135,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND); vma->vm_ops = &hugetlb_vm_ops; - ret = seal_check_future_write(info->seals, vma); + ret = seal_check_write(info->seals, vma); if (ret) return ret; diff --git a/include/linux/mm.h b/include/linux/mm.h index 8e64041b1703..ddf1b35b9dbb 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3775,16 +3775,17 @@ static inline void mem_dump_obj(void *object) {} #endif /** - * seal_check_future_write - Check for F_SEAL_FUTURE_WRITE flag and handle it + * seal_check_write - Check for F_SEAL_WRITE or F_SEAL_FUTURE_WRITE flag and + * handle it. * @seals: the seals to check * @vma: the vma to operate on * - * Check whether F_SEAL_FUTURE_WRITE is set; if so, do proper check/handling on - * the vma flags. Return 0 if check pass, or <0 for errors. + * Check whether F_SEAL_WRITE or F_SEAL_FUTURE_WRITE are set; if so, do proper + * check/handling on the vma flags. Return 0 if check pass, or <0 for errors. */ -static inline int seal_check_future_write(int seals, struct vm_area_struct *vma) +static inline int seal_check_write(int seals, struct vm_area_struct *vma) { - if (seals & F_SEAL_FUTURE_WRITE) { + if (seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) { /* * New PROT_WRITE and MAP_SHARED mmaps are not allowed when * "future write" seal active. @@ -3793,7 +3794,7 @@ static inline int seal_check_future_write(int seals, struct vm_area_struct *vma) return -EPERM; /* - * Since an F_SEAL_FUTURE_WRITE sealed memfd can be mapped as + * Since an F_SEAL_[FUTURE_]WRITE sealed memfd can be mapped as * MAP_SHARED and read-only, take care to not allow mprotect to * revert protections on such mappings. Do this only for shared * mappings. For private mappings, don't need to mask diff --git a/mm/shmem.c b/mm/shmem.c index 9218c955f482..863f2ff9fab8 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2313,7 +2313,7 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma) struct shmem_inode_info *info = SHMEM_I(inode); int ret; - ret = seal_check_future_write(info->seals, vma); + ret = seal_check_write(info->seals, vma); if (ret) return ret; From patchwork Mon Apr 3 22:28:32 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenzo Stoakes X-Patchwork-Id: 78787 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp2630747vqo; Mon, 3 Apr 2023 15:52:11 -0700 (PDT) X-Google-Smtp-Source: AKy350bJtFhjh3RS0A5aiJIakQdeJM4LALHs1boHPSBErPMffYxY6Qc5RRXA/XbhBEJlaPTWLvCp X-Received: by 2002:a17:903:1d1:b0:19e:ecaf:c4b4 with SMTP id e17-20020a17090301d100b0019eecafc4b4mr742723plh.4.1680562331109; Mon, 03 Apr 2023 15:52:11 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1680562331; cv=none; d=google.com; s=arc-20160816; b=dvMLh9vW6h4EmbdOko3cQgvdTinVeCYnR/4AJ8npmKGo/lNLazdsNvSAsldJB1kjBZ XXMAQmo1po6MZsxcpjmZW/h51x/82lqQbdp/RjbjCAsO16rcmY4sBaSYe4rPFE3M9aQR 2iV43d34Saqouik/gW8FYHy53E9V5yC7++ti85MZIusAjB5DujajWiPubg8ZCxWkCBbu +SplsVOiRAMyVk5WVu6rKuatccQnzQ1yH1Sv5mCvPff8wdddy40bQ98tY6N8yK0okmbz qOkksWkk1SiG6O0f+C1ty7gTij5SsIib5k+IF4KnZPDOD+zwANY71/Bb21lD4TkUYDQV +9Gw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=D59V0g1YvYLKaUmx+LEoYjgFSrxRUczBZA1IoL7nlYU=; b=EtKqWz+5+3yAo4Kxai6hnP2EDL58QgPx+CVum4C/tS63HqFs/8/9ZhGfqzvjN9Q5y3 QPwfMNYpU2UjKxPQitYwbN5Q5yQJOT+yTFGAlPW2zdKte+6OCn+xXqrKJ82XMzB83p9F MXDsdy5W7skgcA4x98GtuiHvtlrP1KEUfYtOAHMnw7UPpLvgepuX6xVMJouriwXp6R7O 1Mz2UDHXaZljpDovvDV6aGuX6qg5w8U9bc8xA0SkQhmclvMOXElh8cE97QBX0QXek67f 2HmYw7mXvHiIagYHHuPORND4JWDny+vu7PbmVXnTlEoBR6Fi4nKJK40blxpmQRUop0sG +wzg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20210112 header.b=ETUrq2dY; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from out1.vger.email (out1.vger.email. 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[86.156.84.164]) by smtp.googlemail.com with ESMTPSA id u17-20020a05600c19d100b003dd1bd0b915sm20731309wmq.22.2023.04.03.15.28.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Apr 2023 15:28:44 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Matthew Wilcox , Mike Kravetz , Muchun Song , Alexander Viro , Christian Brauner , Andy Lutomirski , Lorenzo Stoakes Subject: [RFC PATCH 3/3] mm: perform the mapping_map_writable() check after call_mmap() Date: Mon, 3 Apr 2023 23:28:32 +0100 Message-Id: X-Mailer: git-send-email 2.40.0 In-Reply-To: References: MIME-Version: 1.0 X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1762197326612075022?= X-GMAIL-MSGID: =?utf-8?q?1762197326612075022?= In order for a F_SEAL_WRITE sealed memfd mapping to have an opportunity to clear VM_MAYWRITE, we must be able to invoke the appropriate vm_ops->mmap() handler to do so. We would otherwise fail the mapping_map_writable() check before we had the opportunity to avoid it. This patch moves this check after the call_mmap() invocation. Only memfd actively denies write access causing a potential failure here (in memfd_add_seals()), so there should be no impact on non-memfd cases. This patch makes the userland-visible change that MAP_SHARED, PROT_READ mappings of an F_SEAL_WRITE sealed memfd mapping will now succeed. Signed-off-by: Lorenzo Stoakes --- mm/mmap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index c96dcce90772..a166e9f3c474 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2596,17 +2596,17 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma->vm_pgoff = pgoff; if (file) { - if (is_shared_maywrite(vm_flags)) { - error = mapping_map_writable(file->f_mapping); - if (error) - goto free_vma; - } - vma->vm_file = get_file(file); error = call_mmap(file, vma); if (error) goto unmap_and_free_vma; + if (vma_is_shared_maywrite(vma)) { + error = mapping_map_writable(file->f_mapping); + if (error) + goto unmap_and_free_vma; + } + /* * Expansion is handled above, merging is handled below. * Drivers should not alter the address of the VMA.