jbd2: Avoid possible NULL dereference in jbd2_journal_begin_ordered_truncate()
If we race with commit code setting i_transaction to NULL, we could
possibly dereference it. Proper locking requires the journal pointer
(to access journal->j_list_lock), which we don't have. So we have to
change the prototype of the function so that filesystem passes us the
journal pointer. Also add a more detailed comment about why the
function jbd2_journal_begin_ordered_truncate() does what it does and
how it should be used.
Thanks to Dan Carpenter <error27@gmail.com> for pointing to the
suspitious code.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acked-by: Joel Becker <joel.becker@oracle.com>
CC: linux-ext4@vger.kernel.org
CC: ocfs2-devel@oss.oracle.com
CC: mfasheh@suse.de
CC: Dan Carpenter <error27@gmail.com>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 03ba20b..658c4a7 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -47,8 +47,10 @@
static inline int ext4_begin_ordered_truncate(struct inode *inode,
loff_t new_size)
{
- return jbd2_journal_begin_ordered_truncate(&EXT4_I(inode)->jinode,
- new_size);
+ return jbd2_journal_begin_ordered_truncate(
+ EXT4_SB(inode->i_sb)->s_journal,
+ &EXT4_I(inode)->jinode,
+ new_size);
}
static void ext4_invalidatepage(struct page *page, unsigned long offset);