From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 5.10.y 1/4] mm: drop the assumption that VM_SHARED always implies writable
Date: Wed, 30 Jul 2025 12:29:27 -0400 [thread overview]
Message-ID: <1753870943-a9cc6a66@stable.kernel.org> (raw)
In-Reply-To: <20250730015406.32569-2-isaacmanjarres@google.com>
[ Sasha's backport helper bot ]
Hi,
✅ All tests passed successfully. No issues detected.
No action required from the submitter.
The upstream commit SHA1 provided is correct: e8e17ee90eaf650c855adb0a3e5e965fd6692ff1
WARNING: Author mismatch between patch and upstream commit:
Backport author: Isaac J. Manjarres <isaacmanjarres@google.com>
Commit author: Lorenzo Stoakes <lstoakes@gmail.com>
Status in newer kernel trees:
6.15.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Not found
6.1.y | Not found
5.15.y | Not found
Note: The patch differs from the upstream commit:
---
1: e8e17ee90eaf ! 1: 5752dc2ce6f5 mm: drop the assumption that VM_SHARED always implies writable
@@ Metadata
## Commit message ##
mm: drop the assumption that VM_SHARED always implies writable
+ [ Upstream commit e8e17ee90eaf650c855adb0a3e5e965fd6692ff1 ]
+
Patch series "permit write-sealed memfd read-only shared mappings", v4.
The man page for fcntl() describing memfd file seals states the following
@@ Commit message
[1]:https://lore.kernel.org/all/20230324133646.16101dfa666f253c4715d965@linux-foundation.org/
[2]:https://bugzilla.kernel.org/show_bug.cgi?id=217238
-
This patch (of 3):
There is a general assumption that VMAs with the VM_SHARED flag set are
@@ Commit message
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+ Cc: stable@vger.kernel.org
+ [isaacmanjarres: resolved merge conflicts due to
+ due to refactoring that happened in upstream commit
+ 5de195060b2e ("mm: resolve faulty mmap_region() error path behaviour")]
+ Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
## include/linux/fs.h ##
-@@ include/linux/fs.h: extern const struct address_space_operations empty_aops;
- * It is also used to block modification of page cache contents through
- * memory mappings.
+@@ include/linux/fs.h: int pagecache_write_end(struct file *, struct address_space *mapping,
+ * @host: Owner, either the inode or the block_device.
+ * @i_pages: Cached pages.
* @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.
@@ include/linux/mm.h: static inline bool vma_is_accessible(struct vm_area_struct *
+ return is_shared_maywrite(vma->vm_flags);
+}
+
- static inline
- struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max)
- {
+ #ifdef CONFIG_SHMEM
+ /*
+ * The vma_is_shmem is not inline because it is used only by slow
## kernel/fork.c ##
@@ kernel/fork.c: static __latent_entropy int dup_mmap(struct mm_struct *mm,
-
- get_file(file);
+ if (tmp->vm_flags & VM_DENYWRITE)
+ put_write_access(inode);
i_mmap_lock_write(mapping);
- if (tmp->vm_flags & VM_SHARED)
+ if (vma_is_shared_maywrite(tmp))
@@ kernel/fork.c: static __latent_entropy int dup_mmap(struct mm_struct *mm,
/* insert tmp into the share list, just after mpnt */
## mm/filemap.c ##
-@@ mm/filemap.c: int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
+@@ mm/filemap.c: 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)
{
@@ mm/madvise.c: static long madvise_remove(struct vm_area_struct *vma,
offset = (loff_t)(start - vma->vm_start)
## mm/mmap.c ##
-@@ mm/mmap.c: 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)
+@@ mm/mmap.c: static void __remove_shared_vm_struct(struct vm_area_struct *vma,
{
+ if (vma->vm_flags & VM_DENYWRITE)
+ allow_write_access(file);
- if (vma->vm_flags & VM_SHARED)
+ if (vma_is_shared_maywrite(vma))
mapping_unmap_writable(mapping);
flush_dcache_mmap_lock(mapping);
-@@ mm/mmap.c: 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);
-@@ mm/mmap.c: unsigned long mmap_region(struct file *file, unsigned long addr,
- vma->vm_pgoff = pgoff;
+@@ mm/mmap.c: static void __vma_link_file(struct vm_area_struct *vma)
- 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;
-@@ mm/mmap.c: unsigned long mmap_region(struct file *file, unsigned long addr,
- mm->map_count++;
- if (vma->vm_file) {
- i_mmap_lock_write(vma->vm_file->f_mapping);
+ if (vma->vm_flags & VM_DENYWRITE)
+ put_write_access(file_inode(file));
- if (vma->vm_flags & VM_SHARED)
+ if (vma_is_shared_maywrite(vma))
- mapping_allow_writable(vma->vm_file->f_mapping);
+ mapping_allow_writable(mapping);
- flush_dcache_mmap_lock(vma->vm_file->f_mapping);
+ flush_dcache_mmap_lock(mapping);
@@ mm/mmap.c: unsigned long mmap_region(struct file *file, unsigned long addr,
+ return -EINVAL;
- /* 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);
-@@ mm/mmap.c: unsigned long mmap_region(struct file *file, unsigned long addr,
- unmap_region(mm, &vmi.mas, vma, prev, next, vma->vm_start,
- vma->vm_end, 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);
+ /* Map writable and ensure this isn't a sealed memfd. */
+- if (file && (vm_flags & VM_SHARED)) {
++ if (file && is_shared_maywrite(vm_flags)) {
+ int error = mapping_map_writable(file->f_mapping);
+
+ if (error)
---
Results of testing on various branches:
| Branch | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| 5.10 | Success | Success |
next prev parent reply other threads:[~2025-07-30 16:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-30 1:53 [PATCH 5.10.y 0/4] Backport series: "permit write-sealed memfd read-only shared mappings" Isaac J. Manjarres
2025-07-30 1:53 ` [PATCH 5.10.y 1/4] mm: drop the assumption that VM_SHARED always implies writable Isaac J. Manjarres
2025-07-30 16:29 ` Sasha Levin [this message]
2025-07-30 1:54 ` [PATCH 5.10.y 2/4] mm: update memfd seal write check to include F_SEAL_WRITE Isaac J. Manjarres
2025-07-30 16:29 ` Sasha Levin
2025-07-30 1:54 ` [PATCH 5.10.y 3/4] mm: reinstate ability to map write-sealed memfd mappings read-only Isaac J. Manjarres
2025-07-30 16:29 ` Sasha Levin
2025-07-30 1:54 ` [PATCH 5.10.y 4/4] selftests/memfd: add test for mapping write-sealed memfd read-only Isaac J. Manjarres
2025-07-30 16:29 ` Sasha Levin
2025-07-30 14:21 ` [PATCH 5.10.y 0/4] Backport series: "permit write-sealed memfd read-only shared mappings" Lorenzo Stoakes
2025-07-30 17:23 ` Isaac Manjarres
2025-07-30 19:34 ` Lorenzo Stoakes
2025-07-30 22:26 ` Isaac Manjarres
2025-07-31 4:40 ` Lorenzo Stoakes
2025-07-31 4:58 ` Greg KH
2025-07-31 5:02 ` Lorenzo Stoakes
2025-08-06 16:54 ` Isaac Manjarres
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