mm/mmap.c: fix missing call to vm_unacct_memory in mmap_region

stable inclusion
from stable-v4.19.256
commit f84c69bbb3ccc544f0023c4dbbdf922c09b5d80b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5Q0SQ
CVE: NA

--------------------------------

[ Upstream commit 7f82f922319ede486540e8746769865b9508d2c2 ]

Since the beginning, charged is set to 0 to avoid calling vm_unacct_memory
twice because vm_unacct_memory will be called by above unmap_region.  But
since commit 4f74d2c8 ("vm: remove 'nr_accounted' calculations from
the unmap_vmas() interfaces"), unmap_region doesn't call vm_unacct_memory
anymore.  So charged shouldn't be set to 0 now otherwise the calling to
paired vm_unacct_memory will be missed and leads to imbalanced account.

Link: https://lkml.kernel.org/r/20220618082027.43391-1-linmiaohe@huawei.com


Fixes: 4f74d2c8 ("vm: remove 'nr_accounted' calculations from the unmap_vmas() interfaces")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>

mm/mmap.c

@@ -2105,7 +2105,6 @@ static unsigned long __mmap_region(struct mm_struct *mm, struct file *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: