Merge tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linux

Pull MAP_DENYWRITE removal from David Hildenbrand:
 "Remove all in-tree usage of MAP_DENYWRITE from the kernel and remove
  VM_DENYWRITE.

  There are some (minor) user-visible changes:

   - We no longer deny write access to shared libaries loaded via legacy
     uselib(); this behavior matches modern user space e.g. dlopen().

   - We no longer deny write access to the elf interpreter after exec
     completed, treating it just like shared libraries (which it often
     is).

   - We always deny write access to the file linked via /proc/pid/exe:
     sys_prctl(PR_SET_MM_MAP/EXE_FILE) will fail if write access to the
     file cannot be denied, and write access to the file will remain
     denied until the link is effectivel gone (exec, termination,
     sys_prctl(PR_SET_MM_MAP/EXE_FILE)) -- just as if exec'ing the file.

  Cross-compiled for a bunch of architectures (alpha, microblaze, i386,
  s390x, ...) and verified via ltp that especially the relevant tests
  (i.e., creat07 and execve04) continue working as expected"

* tag 'denywrite-for-5.15' of git://github.com/davidhildenbrand/linux:
  fs: update documentation of get_write_access() and friends
  mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff()
  mm: remove VM_DENYWRITE
  binfmt: remove in-tree usage of MAP_DENYWRITE
  kernel/fork: always deny write access to current MM exe_file
  kernel/fork: factor out replacing the current MM exe_file
  binfmt: don't use MAP_DENYWRITE when loading shared libraries via uselib()

2 files changed, 3 insertions, 28 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index dce46105e3df..88dcc5c25225 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -148,8 +148,6 @@ 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_DENYWRITE)
-		allow_write_access(file);
 	if (vma->vm_flags & VM_SHARED)
 		mapping_unmap_writable(mapping);
 
@@ -667,8 +665,6 @@ static void __vma_link_file(struct vm_area_struct *vma)
 	if (file) {
 		struct address_space *mapping = file->f_mapping;
 
-		if (vma->vm_flags & VM_DENYWRITE)
-			put_write_access(file_inode(file));
 		if (vma->vm_flags & VM_SHARED)
 			mapping_allow_writable(mapping);
 
@@ -1625,8 +1621,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
 			return PTR_ERR(file);
 	}
 
-	flags &= ~MAP_DENYWRITE;
-
 	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
 out_fput:
 	if (file)
@@ -1783,22 +1777,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	vma->vm_pgoff = pgoff;
 
 	if (file) {
-		if (vm_flags & VM_DENYWRITE) {
-			error = deny_write_access(file);
-			if (error)
-				goto free_vma;
-		}
 		if (vm_flags & VM_SHARED) {
 			error = mapping_map_writable(file->f_mapping);
 			if (error)
-				goto allow_write_and_free_vma;
+				goto free_vma;
 		}
 
-		/* ->mmap() can change vma->vm_file, but must guarantee that
-		 * vma_link() below can deny write-access if VM_DENYWRITE is set
-		 * and map writably if VM_SHARED is set. This usually means the
-		 * new file must not have been exposed to user-space, yet.
-		 */
 		vma->vm_file = get_file(file);
 		error = call_mmap(file, vma);
 		if (error)
@@ -1855,13 +1839,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 
 	vma_link(mm, vma, prev, rb_link, rb_parent);
 	/* Once vma denies write, undo our temporary denial count */
-	if (file) {
 unmap_writable:
-		if (vm_flags & VM_SHARED)
-			mapping_unmap_writable(file->f_mapping);
-		if (vm_flags & VM_DENYWRITE)
-			allow_write_access(file);
-	}
+	if (file && vm_flags & VM_SHARED)
+		mapping_unmap_writable(file->f_mapping);
 	file = vma->vm_file;
 out:
 	perf_event_mmap(vma);
@@ -1901,9 +1881,6 @@ unmap_and_free_vma:
 	charged = 0;
 	if (vm_flags & VM_SHARED)
 		mapping_unmap_writable(file->f_mapping);
-allow_write_and_free_vma:
-	if (vm_flags & VM_DENYWRITE)
-		allow_write_access(file);
 free_vma:
 	vm_area_free(vma);
 unacct_error:
diff --git a/mm/nommu.c b/mm/nommu.c
index 9d0ad98f838c..02d2427b8f9e 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1293,8 +1293,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
 			goto out;
 	}
 
-	flags &= ~MAP_DENYWRITE;
-
 	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
 
 	if (file)