ext2: fix unbalanced kmap()/kunmap()

In ext2_rename(), dir_page is acquired through ext2_dotdot().  It is
then released through ext2_set_link() but only if old_dir != new_dir.
Failing that, the pkmap reference count is never decremented and the
page remains pinned forever.  Repeat that a couple times with highmem
pages and all pkmap slots get exhausted, and every further kmap() calls
end up stalling on the pkmap_map_wait queue at which point the whole
system comes to a halt.

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Acked-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index e1dedb0f7873..78d9b925fc94 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -362,6 +362,10 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
         if (dir_de) {
                 if (old_dir != new_dir)
                         ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
+                else {
+                        kunmap(dir_page);
+                        page_cache_release(dir_page);
+                }
                 inode_dec_link_count(old_dir);
         }
         return 0;