From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 11 Sep 2013 21:20:18 +0000 (-0700)
Subject: mm: shift VM_GROWS* check from mmap_region() to do_mmap_pgoff()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=475069d6426ba9cd7f21886bfe7da352ec6d5582;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git

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: Oleg Nesterov <oleg@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: Ic81c1919adf051b9308125fcb87ae6a46e71b580
---

diff --git a/mm/mmap.c b/mm/mmap.c
index 0d8840efa27..3aa6e3524d7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1342,6 +1342,8 @@ 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:
@@ -1350,6 +1352,8 @@ 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.
 			 */
@@ -1583,11 +1587,7 @@ munmap_back:
 	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)
@@ -1612,8 +1612,6 @@ munmap_back:
 		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;