Messages in this thread Patch in this message | | | From | Chen Wandun <> | Subject | [PATCH] mm/mremap: fix memory account on do_munmap() failure | Date | Sat, 17 Jul 2021 18:19:42 +0800 |
| |
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.
Fixes: 51df7bcb6151 ("mm/mremap: account memory on do_munmap() failure") Signed-off-by: Chen Wandun <chenwandun@huawei.com> --- mm/mremap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/mremap.c b/mm/mremap.c index 5989d3990020..badfe17ade1f 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -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) { /* 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; } -- 2.25.1
| |