+ mm-update-memfd-seal-write-check-to-include-f_seal_write.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: update memfd seal write check to include F_SEAL_WRITE
has been added to the -mm mm-unstable branch.  Its filename is
     mm-update-memfd-seal-write-check-to-include-f_seal_write.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-update-memfd-seal-write-check-to-include-f_seal_write.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Lorenzo Stoakes <lstoakes@gmail.com>
Subject: mm: update memfd seal write check to include F_SEAL_WRITE
Date: Sat, 7 Oct 2023 21:51:00 +0100

The seal_check_future_write() function is called by shmem_mmap() or
hugetlbfs_file_mmap() to disallow any future writable mappings of an memfd
sealed this way.

The F_SEAL_WRITE flag is not checked here, as that is handled via the
mapping->i_mmap_writable mechanism and so any attempt at a mapping would
fail before this could be run.

However we intend to change this, meaning this check can be performed for
F_SEAL_WRITE mappings also.

The logic here is equally applicable to both flags, so update this
function to accommodate both and rename it accordingly.

Link: https://lkml.kernel.org/r/f33faf83fe231441b41a8eeb170e9212b346c547.1696709413.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/hugetlbfs/inode.c |    2 +-
 include/linux/mm.h   |   15 ++++++++-------
 mm/shmem.c           |    2 +-
 3 files changed, 10 insertions(+), 9 deletions(-)

--- a/fs/hugetlbfs/inode.c~mm-update-memfd-seal-write-check-to-include-f_seal_write
+++ a/fs/hugetlbfs/inode.c
@@ -112,7 +112,7 @@ static int hugetlbfs_file_mmap(struct fi
 	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;
 
--- a/include/linux/mm.h~mm-update-memfd-seal-write-check-to-include-f_seal_write
+++ a/include/linux/mm.h
@@ -4078,25 +4078,26 @@ static inline void mem_dump_obj(void *ob
 #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 flags and
+ *                    handle them.
  * @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.
+		 * write seals are active.
 		 */
 		if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_WRITE))
 			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
--- a/mm/shmem.c~mm-update-memfd-seal-write-check-to-include-f_seal_write
+++ a/mm/shmem.c
@@ -2405,7 +2405,7 @@ static int shmem_mmap(struct file *file,
 	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;
 
_

Patches currently in -mm which might be from lstoakes@gmail.com are

mm-filemap-clarify-filemap_fault-comments-for-not-uptodate-case.patch
mm-filemap-clarify-filemap_fault-comments-for-not-uptodate-case-fix.patch
mm-make-__access_remote_vm-static.patch
mm-gup-explicitly-define-and-check-internal-gup-flags-disallow-foll_touch.patch
mm-gup-make-failure-to-pin-an-error-if-foll_nowait-not-specified.patch
mm-gup-adapt-get_user_page_vma_remote-to-never-return-null.patch
mm-move-vma_policy-and-anon_vma_name-decls-to-mm_typesh.patch
mm-abstract-the-vma_merge-split_vma-pattern-for-mprotect-et-al.patch
mm-make-vma_merge-and-split_vma-internal.patch
mm-abstract-merge-for-new-vmas-into-vma_merge_new_vma.patch
mm-abstract-vma-merge-and-extend-into-vma_merge_extend-helper.patch
mm-drop-the-assumption-that-vm_shared-always-implies-writable.patch
mm-update-memfd-seal-write-check-to-include-f_seal_write.patch
mm-enforce-the-mapping_map_writable-check-after-call_mmap.patch