Merge branch 'akpm' (second patchbomb from Andrew Morton)

Merge more incoming from Andrew Morton:
 "Two new syscalls:

     memfd_create in "shm: add memfd_create() syscall"
     kexec_file_load in "kexec: implementation of new syscall kexec_file_load"

  And:

   - Most (all?) of the rest of MM

   - Lots of the usual misc bits

   - fs/autofs4

   - drivers/rtc

   - fs/nilfs

   - procfs

   - fork.c, exec.c

   - more in lib/

   - rapidio

   - Janitorial work in filesystems: fs/ufs, fs/reiserfs, fs/adfs,
     fs/cramfs, fs/romfs, fs/qnx6.

   - initrd/initramfs work

   - "file sealing" and the memfd_create() syscall, in tmpfs

   - add pci_zalloc_consistent, use it in lots of places

   - MAINTAINERS maintenance

   - kexec feature work"

* emailed patches from Andrew Morton <akpm@linux-foundation.org: (193 commits)
  MAINTAINERS: update nomadik patterns
  MAINTAINERS: update usb/gadget patterns
  MAINTAINERS: update DMA BUFFER SHARING patterns
  kexec: verify the signature of signed PE bzImage
  kexec: support kexec/kdump on EFI systems
  kexec: support for kexec on panic using new system call
  kexec-bzImage64: support for loading bzImage using 64bit entry
  kexec: load and relocate purgatory at kernel load time
  purgatory: core purgatory functionality
  purgatory/sha256: provide implementation of sha256 in purgaotory context
  kexec: implementation of new syscall kexec_file_load
  kexec: new syscall kexec_file_load() declaration
  kexec: make kexec_segment user buffer pointer a union
  resource: provide new functions to walk through resources
  kexec: use common function for kimage_normal_alloc() and kimage_crash_alloc()
  kexec: move segment verification code in a separate function
  kexec: rename unusebale_pages to unusable_pages
  kernel: build bin2c based on config option CONFIG_BUILD_BIN2C
  bin2c: move bin2c in scripts/basic
  shm: wait for pins to be released when sealing
  ...

1 files changed, 24 insertions, 6 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 64c9d736155c..c1f2ea4a0b99 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -221,7 +221,7 @@ static void __remove_shared_vm_struct(struct vm_area_struct *vma,
 	if (vma->vm_flags & VM_DENYWRITE)
 		atomic_inc(&file_inode(file)->i_writecount);
 	if (vma->vm_flags & VM_SHARED)
-		mapping->i_mmap_writable--;
+		mapping_unmap_writable(mapping);
 
 	flush_dcache_mmap_lock(mapping);
 	if (unlikely(vma->vm_flags & VM_NONLINEAR))
@@ -622,7 +622,7 @@ static void __vma_link_file(struct vm_area_struct *vma)
 		if (vma->vm_flags & VM_DENYWRITE)
 			atomic_dec(&file_inode(file)->i_writecount);
 		if (vma->vm_flags & VM_SHARED)
-			mapping->i_mmap_writable++;
+			atomic_inc(&mapping->i_mmap_writable);
 
 		flush_dcache_mmap_lock(mapping);
 		if (unlikely(vma->vm_flags & VM_NONLINEAR))
@@ -1577,6 +1577,17 @@ munmap_back:
 			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;
+		}
+
+		/* ->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 = file->f_op->mmap(file, vma);
 		if (error)
@@ -1616,8 +1627,12 @@ munmap_back:
 
 	vma_link(mm, vma, prev, rb_link, rb_parent);
 	/* Once vma denies write, undo our temporary denial count */
-	if (vm_flags & VM_DENYWRITE)
-		allow_write_access(file);
+	if (file) {
+		if (vm_flags & VM_SHARED)
+			mapping_unmap_writable(file->f_mapping);
+		if (vm_flags & VM_DENYWRITE)
+			allow_write_access(file);
+	}
 	file = vma->vm_file;
 out:
 	perf_event_mmap(vma);
@@ -1646,14 +1661,17 @@ out:
 	return addr;
 
 unmap_and_free_vma:
-	if (vm_flags & VM_DENYWRITE)
-		allow_write_access(file);
 	vma->vm_file = NULL;
 	fput(file);
 
 	/* Undo any partial mapping done by a device driver. */
 	unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
 	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:
 	kmem_cache_free(vm_area_cachep, vma);
 unacct_error: