[PATCH] fix mempolicy's check on a system with memory-less-node

bind_zonelist() can create zero-length zonelist if there is a
memory-less-node.  This patch checks the length of zonelist.  If length is
0, returns -EINVAL.

tested on ia64/NUMA with memory-less-node.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Andi Kleen <ak@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 259a706bd83e..cf2a5381030a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -144,7 +144,7 @@ static struct zonelist *bind_zonelist(nodemask_t *nodes)
         max++;                  /* space for zlcache_ptr (see mmzone.h) */
         zl = kmalloc(sizeof(struct zone *) * max, GFP_KERNEL);
         if (!zl)
-                return NULL;
+                return ERR_PTR(-ENOMEM);
         zl->zlcache_ptr = NULL;
         num = 0;
         /* First put in the highest zones from all nodes, then all the next 
@@ -162,6 +162,10 @@ static struct zonelist *bind_zonelist(nodemask_t *nodes)
                         break;
                 k--;
         }
+        if (num == 0) {
+                kfree(zl);
+                return ERR_PTR(-EINVAL);
+        }
         zl->zones[num] = NULL;
         return zl;
 }
@@ -193,9 +197,10 @@ static struct mempolicy *mpol_new(int mode, nodemask_t *nodes)
                 break;
         case MPOL_BIND:
                 policy->v.zonelist = bind_zonelist(nodes);
-                if (policy->v.zonelist == NULL) {
+                if (IS_ERR(policy->v.zonelist)) {
+                        void *error_code = policy->v.zonelist;
                         kmem_cache_free(policy_cache, policy);
-                        return ERR_PTR(-ENOMEM);
+                        return error_code;
                 }
                 break;
         }
@@ -1667,7 +1672,7 @@ void mpol_rebind_policy(struct mempolicy *pol, const nodemask_t *newmask)
                  * then zonelist_policy() will "FALL THROUGH" to MPOL_DEFAULT.
                  */
 
-                if (zonelist) {
+                if (!IS_ERR(zonelist)) {
                         /* Good - got mem - substitute new zonelist */
                         kfree(pol->v.zonelist);
                         pol->v.zonelist = zonelist;