f2fs: fix a problem of using memory after free

commit 7855eba4d6102f811b6dd142d6c749f53b591fa3 upstream.

This patch fix a problem of using memory after free
in function __try_merge_extent_node.

Fixes: 0f825ee6e873 ("f2fs: add new interfaces for extent tree")
Signed-off-by: Yunlei He <heyunlei@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 2b06d4fcd954..7b32ce979fe1 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -352,11 +352,12 @@ static struct extent_node *__try_merge_extent_node(struct inode *inode,
         }
 
         if (next_ex && __is_front_mergeable(ei, &next_ex->ei)) {
-                if (en)
-                        __release_extent_node(sbi, et, prev_ex);
                 next_ex->ei.fofs = ei->fofs;
                 next_ex->ei.blk = ei->blk;
                 next_ex->ei.len += ei->len;
+                if (en)
+                        __release_extent_node(sbi, et, prev_ex);
+
                 en = next_ex;
         }