From 23800bff6fa346a4e9b3806dc0cfeb74498df757 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Mon, 6 Apr 2020 20:40:13 -0400 Subject: [PATCH] mm/mempolicy: Allow lookup_node() to handle fatal signal lookup_node() uses gup to pin the page and get node information. It checks against ret>=0 assuming the page will be filled in. However it's also possible that gup will return zero, for example, when the thread is quickly killed with a fatal signal. Teach lookup_node() to gracefully return an error -EFAULT if it happens. Reported-by: syzbot+693dc11fcb53120b5559@syzkaller.appspotmail.com Fixes: 4426e945df58 ("mm/gup: allow VM_FAULT_RETRY for multiple times") Signed-off-by: Peter Xu --- mm/mempolicy.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 5fb427aed61279..1398578db02563 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -902,7 +902,10 @@ static int lookup_node(struct mm_struct *mm, unsigned long addr) int locked = 1; err = get_user_pages_locked(addr & PAGE_MASK, 1, 0, &p, &locked); - if (err >= 0) { + if (err == 0) { + /* E.g. GUP interupted by fatal signal */ + err = -EFAULT; + } else if (err > 0) { err = page_to_nid(p); put_page(p); }