From ae7987835643e470cb220e6685bd36d92179ef9c Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Mon, 23 May 2016 16:25:33 -0700 Subject: [PATCH] mm: make vm_munmap killable Almost all current users of vm_munmap are ignoring the return value and so they do not handle potential error. This means that some VMAs might stay behind. This patch doesn't try to solve those potential problems. Quite contrary it adds a new failure mode by using down_write_killable in vm_munmap. This should be safer than other failure modes, though, because the process is guaranteed to die as soon as it leaves the kernel and exit_mmap will clean the whole address space. This will help in the OOM conditions when the oom victim might be stuck waiting for the mmap_sem for write which in turn can block oom_reaper which relies on the mmap_sem for read to make a forward progress and reclaim the address space of the victim. Signed-off-by: Michal Hocko Cc: Oleg Nesterov Cc: "Kirill A. Shutemov" Cc: Konstantin Khlebnikov Cc: Andrea Arcangeli Cc: Alexander Viro Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mmap.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 420088682d4a..ca292a7c2b68 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2494,11 +2494,9 @@ int vm_munmap(unsigned long start, size_t len) int ret; struct mm_struct *mm = current->mm; - /* - * XXX convert to down_write_killable as soon as all users are able - * to handle the error. - */ - down_write(&mm->mmap_sem); + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + ret = do_munmap(mm, start, len); up_write(&mm->mmap_sem); return ret; -- 2.20.1