Commit 5e22928a authored by Chen Wandun's avatar Chen Wandun Committed by Linus Torvalds

mm/mremap: fix memory account on do_munmap() failure

mremap will account the delta between new_len and old_len in
vma_to_resize, and then call move_vma when expanding an existing memory
mapping.  In function move_vma, there are two scenarios when calling
do_munmap:

1. move_page_tables from old_addr to new_addr success
2. move_page_tables from old_addr to new_addr fail

In first scenario, it should account old_len if do_munmap fail, because
the delta has already been accounted.

In second scenario, new_addr/new_len will assign to old_addr/old_len if
move_page_table fail, so do_munmap is try to unmap new_addr actually, if
do_munmap fail, it should account the new_len, because error code will be
return from move_vma, and delta will be unaccounted.  What'more, because
of new_len == old_len, so account old_len also is OK.

In summary, account old_len will be correct if do_munmap fail.

Link: https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
Fixes: 51df7bcb ("mm/mremap: account memory on do_munmap() failure")
Signed-off-by: default avatarChen Wandun <chenwandun@huawei.com>
Acked-by: default avatarDmitry Safonov <dima@arista.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9b593cb2
...@@ -686,7 +686,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, ...@@ -686,7 +686,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
/* OOM: unable to split vma, just get accounts right */ /* OOM: unable to split vma, just get accounts right */
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
vm_acct_memory(new_len >> PAGE_SHIFT); vm_acct_memory(old_len >> PAGE_SHIFT);
excess = 0; excess = 0;
} }
......
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