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Commit b2c56e4f authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

mm: shift VM_GROWS* check from mmap_region() to do_mmap_pgoff() 



mmap() doesn't allow the non-anonymous mappings with VM_GROWS* bit set.
In particular this means that mmap_region()->vma_merge(file, vm_flags)
must always fail if "vm_flags & VM_GROWS" is set incorrectly.

So it does not make sense to check VM_GROWS* after we already allocated
the new vma, the only caller, do_mmap_pgoff(), which can pass this flag
can do the check itself.

And this looks a bit more correct, mmap_region() already unmapped the
old mapping at this stage. But if mmap() is going to fail, it should
avoid do_munmap() if possible.

Note: we check VM_GROWS at the end to ensure that do_mmap_pgoff() won't
return EINVAL in the case when it currently returns another error code.

Many thanks to Hugh who nacked the buggy v1.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 465c47fd

mm/mmap.c

+4 −6
Original line number Diff line number Diff line
@@ -1302,6 +1302,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, 


			if (!file->f_op || !file->f_op->mmap)

				return -ENODEV;

			if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))

				return -EINVAL;

			break;



		default:
@@ -1310,6 +1312,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, 
	} else {

		switch (flags & MAP_TYPE) {

		case MAP_SHARED:

			if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))

				return -EINVAL;

			/*

			 * Ignore pgoff.

			 */
@@ -1544,11 +1548,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
	vma->vm_pgoff = pgoff;

	INIT_LIST_HEAD(&vma->anon_vma_chain);



	error = -EINVAL;	/* when rejecting VM_GROWSDOWN|VM_GROWSUP */



	if (file) {

		if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))

			goto free_vma;

		if (vm_flags & VM_DENYWRITE) {

			error = deny_write_access(file);

			if (error)
@@ -1573,8 +1573,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr, 
		pgoff = vma->vm_pgoff;

		vm_flags = vma->vm_flags;

	} else if (vm_flags & VM_SHARED) {

		if (unlikely(vm_flags & (VM_GROWSDOWN|VM_GROWSUP)))

			goto free_vma;

		error = shmem_zero_setup(vma);

		if (error)

			goto free_vma;