ksm: check for ERR_PTR from follow_page()

The follow_page() function can potentially return -EFAULT so I added
checks for this.

Also I silenced an uninitialized variable warning on my version of gcc
(version 4.3.2).

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 8cdfc2a1e8bf..956880f2ff49 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -365,7 +365,7 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
         do {
                 cond_resched();
                 page = follow_page(vma, addr, FOLL_GET);
-                if (!page)
+                if (IS_ERR_OR_NULL(page))
                         break;
                 if (PageKsm(page))
                         ret = handle_mm_fault(vma->vm_mm, vma, addr,
@@ -447,7 +447,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
                 goto out;
 
         page = follow_page(vma, addr, FOLL_GET);
-        if (!page)
+        if (IS_ERR_OR_NULL(page))
                 goto out;
         if (PageAnon(page)) {
                 flush_anon_page(vma, page, addr);
@@ -1086,7 +1086,7 @@ struct rmap_item *unstable_tree_search_insert(struct rmap_item *rmap_item,
                 cond_resched();
                 tree_rmap_item = rb_entry(*new, struct rmap_item, node);
                 tree_page = get_mergeable_page(tree_rmap_item);
-                if (!tree_page)
+                if (IS_ERR_OR_NULL(tree_page))
                         return NULL;
 
                 /*
@@ -1294,7 +1294,7 @@ next_mm:
                         if (ksm_test_exit(mm))
                                 break;
                         *page = follow_page(vma, ksm_scan.address, FOLL_GET);
-                        if (*page && PageAnon(*page)) {
+                        if (!IS_ERR_OR_NULL(*page) && PageAnon(*page)) {
                                 flush_anon_page(vma, *page, ksm_scan.address);
                                 flush_dcache_page(*page);
                                 rmap_item = get_next_rmap_item(slot,
@@ -1308,7 +1308,7 @@ next_mm:
                                 up_read(&mm->mmap_sem);
                                 return rmap_item;
                         }
-                        if (*page)
+                        if (!IS_ERR_OR_NULL(*page))
                                 put_page(*page);
                         ksm_scan.address += PAGE_SIZE;
                         cond_resched();
@@ -1367,7 +1367,7 @@ next_mm:
 static void ksm_do_scan(unsigned int scan_npages)
 {
         struct rmap_item *rmap_item;
-        struct page *page;
+        struct page *uninitialized_var(page);
 
         while (scan_npages--) {
                 cond_resched();