mm/mempolicy.c: avoid use uninitialized preferred_node

Alexander reported a use of uninitialized memory in __mpol_equal(), which is caused by incorrect use of preferred_node. When mempolicy in mode MPOL_PREFERRED with flags MPOL_F_LOCAL, it uses numa_node_id() instead of preferred_node, however, __mpol_equal() uses preferred_node without checking whether it is MPOL_F_LOCAL or not. [[email protected]: slight comment tweak] Link: http://lkml.kernel.org/r/[email protected] Fixes: fc36b8d ("mempolicy: use MPOL_F_LOCAL to Indicate Preferred Local Policy") Signed-off-by: Yisheng Xie <[email protected]> Reported-by: Alexander Potapenko <[email protected]> Tested-by: Alexander Potapenko <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: Dmitriy Vyukov <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Michal Hocko <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
josf · Mar 23, 2018 · 8970a63 · 8970a63
1 parent 3215b9d
commit 8970a63
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
@@ -2124,6 +2124,9 @@ bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
 	case MPOL_INTERLEAVE:
 		return !!nodes_equal(a->v.nodes, b->v.nodes);
 	case MPOL_PREFERRED:
+		/* a's ->flags is the same as b's */
+		if (a->flags & MPOL_F_LOCAL)
+			return true;
 		return a->v.preferred_node == b->v.preferred_node;
 	default:
 		BUG();