f2fs: fix null page reference in redirty_blocks

By Colin's static analysis, we found out there is a null page reference
under low memory situation in redirty_blocks. I've made the page finding
loop stop immediately and return an error not to cause further memory
pressure when we run into a failure to find a page under low memory
condition.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reported-by: Colin Ian King <colin.king@canonical.com>
Fixes: 5fdb322ff2c2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
Reviewed-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 4e6d4b9120a86bde54cb9bfe7698855eecc1ecf1..e3a5b620b50aea05e74451e8f9dbc0359f59fd50 100644 (file)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4057,8 +4057,10 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 
        for (i = 0; i < page_len; i++, redirty_idx++) {
                page = find_lock_page(mapping, redirty_idx);
-               if (!page)
-                       ret = -ENOENT;
+               if (!page) {
+                       ret = -ENOMEM;
+                       break;
+               }
                set_page_dirty(page);
                f2fs_put_page(page, 1);
                f2fs_put_page(page, 0);