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authorMichal Hocko <mhocko@suse.com>2020-06-04 02:03:25 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-04 06:09:49 +0300
commit2d3a36a47964371101d9a71691c18d59ee611e87 (patch)
tree7095a011438bf9ee1fac60a18ce6bb336b19d2f3 /mm/mempolicy.c
parent5b94ce2fcae2542c4d5d49176fa23eea638dc7b6 (diff)
downloadlinux-2d3a36a47964371101d9a71691c18d59ee611e87.tar.xz
mm, mempolicy: fix up gup usage in lookup_node
ba841078cd05 ("mm/mempolicy: Allow lookup_node() to handle fatal signal") has added a special casing for 0 return value because that was a possible gup return value when interrupted by fatal signal. This has been fixed by ae46d2aa6a7f ("mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal") in the mean time so ba841078cd05 can be reverted. This patch however doesn't go all the way to revert it because the check for 0 is wrong and confusing here. Firstly it is inherently unsafe to access the page when get_user_pages_locked returns 0 (aka no page returned). Fortunatelly this will not happen because get_user_pages_locked will not return 0 when nr_pages > 0 unless FOLL_NOWAIT is specified which is not the case here. Document this potential error code in gup code while we are at it. Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Xu <peterx@redhat.com> Link: http://lkml.kernel.org/r/20200421071026.18394-1-mhocko@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mempolicy.c')
-rw-r--r--mm/mempolicy.c5
1 files changed, 1 insertions, 4 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 48ba9729062e..1965e2681877 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -927,10 +927,7 @@ 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) {
- /* E.g. GUP interrupted by fatal signal */
- err = -EFAULT;
- } else if (err > 0) {
+ if (err > 0) {
err = page_to_nid(p);
put_page(p);
}