ext4: make sure directory and symlink blocks are revoked

When an inode gets unlinked, the functions ext4_clear_blocks() and
ext4_remove_blocks() call ext4_forget() for all the buffer heads
corresponding to the deleted inode's data blocks.  If the inode is a
directory or a symlink, the is_metadata parameter must be non-zero so
ext4_forget() will revoke them via jbd2_journal_revoke().  Otherwise,
if these blocks are reused for a data file, and the system crashes
before a journal checkpoint, the journal replay could end up
corrupting these data blocks.

Thanks to Curt Wohlgemuth for pointing out potential problems in this
area.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 13de1dd751f5..c420aaba6e9c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4121,6 +4121,8 @@ static void ext4_clear_blocks(handle_t *handle, struct inode *inode,
                               __le32 *last)
 {
         __le32 *p;
+        int     is_metadata = S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode);
+
         if (try_to_extend_transaction(handle, inode)) {
                 if (bh) {
                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
@@ -4151,11 +4153,11 @@ static void ext4_clear_blocks(handle_t *handle, struct inode *inode,
 
                         *p = 0;
                         tbh = sb_find_get_block(inode->i_sb, nr);
-                        ext4_forget(handle, 0, inode, tbh, nr);
+                        ext4_forget(handle, is_metadata, inode, tbh, nr);
                 }
         }
 
-        ext4_free_blocks(handle, inode, block_to_free, count, 0);
+        ext4_free_blocks(handle, inode, block_to_free, count, is_metadata);
 }
 
 /**