From: Chen Wandun <chenwandun@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Fixes: 51df7bcb6151 ("mm/mremap: account memory on do_munmap() failure") Signed-off-by: Chen Wandun <chenwandun@xxxxxxxxxx> Acked-by: Dmitry Safonov <dima@xxxxxxxxxx> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Cc: Wei Yongjun <weiyongjun1@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mremap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/mremap.c~mm-mremap-fix-memory-account-on-do_munmap-failure +++ a/mm/mremap.c @@ -686,7 +686,7 @@ static unsigned long move_vma(struct vm_ if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { /* OOM: unable to split vma, just get accounts right */ if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) - vm_acct_memory(new_len >> PAGE_SHIFT); + vm_acct_memory(old_len >> PAGE_SHIFT); excess = 0; } _
