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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 67495ef79bb2..874fe0e38e65 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -413,7 +413,7 @@ 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. @@ -516,7 +516,7 @@ 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 27ce77080c79..3e8fb4601520 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -851,6 +851,17 @@ 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 4342200d5e2b..7ebd6229219a 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 b5ffbaf616f5..5eb59854e285 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -969,7 +969,7 @@ 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 5522130ae606..646e34e95a37 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -107,7 +107,7 @@ 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); @@ -428,7 +428,7 @@ 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); @@ -2642,7 +2642,7 @@ 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; @@ -2717,7 +2717,7 @@ 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); @@ -2734,7 +2734,7 @@ 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; ksm_add_vma(vma); @@ -2781,7 +2781,7 @@ 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 Sun Apr 30 22:26:06 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenzo Stoakes X-Patchwork-Id: 88963 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp2369420vqo; Sun, 30 Apr 2023 16:18:49 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ6RJ5zhZgOXfHvVwdPmjb73repkaR78/663Eooy5dREWZwzhrQsQdh2WqgzTJoBANwLE5AF X-Received: by 2002:a05:6a00:ac6:b0:62a:4503:53ba with SMTP id c6-20020a056a000ac600b0062a450353bamr18309523pfl.26.1682896729431; Sun, 30 Apr 2023 16:18:49 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1682896729; cv=none; d=google.com; s=arc-20160816; b=vRQ8lnjGqvllLqItzZ6ZPM/9GPR/EW2kLJBXrl6xDAsD7MF3/NLcfbKWHGiG6lJnV4 i5akUjE7J+vjQFJp8rKuCUbdtUymur1bmHFhYdoLdXUU+5zAlzoct3gzzD57NT+BXDBR /i3kbmJd2pHQlEvuqZ2I39+Ugzp+kFgtxuLAZ8B00X/7cq2OR52qw0Pg/tkTOhkXfEUN rV1B7hmlDYUYcVNmR6GXgx5UfqjzMHq8AdOeEwpNW/cuAAX67+CE1LI3SofRN4DglVRO JXND4G8b5phJh11WpSLVSCe0/4WYEDj9ChQYQHTPcFaD/PLpbI51s2tKzdQd7w5jk2Uy ZUXQ== ARC-Message-Signature: i=1; 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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 ecfdfb2529a3..4abe3d4a6d1c 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 3e8fb4601520..6bf63ee1b769 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3784,16 +3784,17 @@ 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. @@ -3802,7 +3803,7 @@ 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 e517ab50afd9..c54df8e36bc1 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2325,7 +2325,7 @@ 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 Sun Apr 30 22:26:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenzo Stoakes X-Patchwork-Id: 88959 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp2355150vqo; Sun, 30 Apr 2023 15:37:40 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ5BJgkgPNT+6/JvYnSHmKuT2gA06gxjqTG5qBvGF7jVBLrBRI6qxklc52Aj2nTLd+rhl8c0 X-Received: by 2002:a17:90a:f581:b0:247:6ec8:7e9b with SMTP id ct1-20020a17090af58100b002476ec87e9bmr12240603pjb.44.1682894259727; Sun, 30 Apr 2023 15:37:39 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1682894259; cv=none; d=google.com; s=arc-20160816; b=Ffouf+riyrRmu56rHu9+jEx2u8rjPYbYUUG2TvkvvmHLGfZB1GgUpqeAWWuT9yIFFt /JP5HPNljRKB7nl9+CUixWiA41cNhN/MDSmIY9TMHPWyyWN7XO1hS5kudV1xEwkBedig xyaU2hy0bjwta9DTpq9hUqSanymi8xjOkgaJxrYRcT9xQ391bHBIPDhAu9JsfU095Eg/ ycbLXXjVw3yGQlPc2llYDKu2nRA5E/A7zWuYldcowRpkZNfDmSnEpUN1xAWJt28xXoOR a/ACRa9VqW3/Te9PNI1NFgbJd0kwJTHg8vWNKL+babeoojvh0g55F6PFQQFpy1/QQXI4 hj3A== 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=gU5klj4JuCtxBh6JR6WjnJXM2yce7ELIzVSpcWZL9RY=; b=NnStOsdomo4ukDuC1lSquhcDrKz+hNSaKXi/UNCjQPS6aJ9seJ9Ke003/SPoE3rqHI LNlmITdMc9T4olCJab/EjvfcssHKgN2x6gnNIA3JLHZau6pivFJ+13BU21KacqRCeZV/ AANGnYp0QWqoKQoyPSpmdLg9Aen/WoaWEtbw3dj54JcWau7HMNRsLjFstF/cM18CMLbZ fE7qWch/FoyUVGBOydyvbfvYAA1uPIIysPIJjDnABnTm3t1AYHUiur1EPgWMezAbJ5QB m9zvMKlfPA3AKMDiv8FWvquInJY7e7KDfYWuBO3FLVfxBmIC3BHft+6tppj0KMSxgo5s Xmrw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20221208 header.b=VXNNdRhL; 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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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. Link: https://bugzilla.kernel.org/show_bug.cgi?id=217238 Signed-off-by: Lorenzo Stoakes --- mm/mmap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) -- 2.40.1 diff --git a/mm/mmap.c b/mm/mmap.c index 646e34e95a37..1608d7f5a293 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2642,17 +2642,17 @@ 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 close_and_free_vma; + } + /* * Expansion is handled above, merging is handled below. * Drivers should not alter the address of the VMA.