Btrfs: avoid possible NULL deref in io_ctl_drop_pages()

If we run into some failure path in io_ctl_prepare_pages(),
io_ctl->pages[] array may have some NULL pointers.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 01840ef95a32..4e55af333e19 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -319,9 +319,11 @@ static void io_ctl_drop_pages(struct io_ctl *io_ctl)
         io_ctl_unmap_page(io_ctl);
 
         for (i = 0; i < io_ctl->num_pages; i++) {
-                ClearPageChecked(io_ctl->pages[i]);
-                unlock_page(io_ctl->pages[i]);
-                page_cache_release(io_ctl->pages[i]);
+                if (io_ctl->pages[i]) {
+                        ClearPageChecked(io_ctl->pages[i]);
+                        unlock_page(io_ctl->pages[i]);
+                        page_cache_release(io_ctl->pages[i]);
+                }
         }
 }