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jbd2: Avoid possible NULL dereference in jbd2_journal_begin_ordered_truncate()

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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>
This commit is contained in:
Jan Kara
2009-02-10 11:15:34 -05:00
committed by Theodore Tso
parent 9eddacf9e9
commit 7f5aa21508
4 changed files with 41 additions and 16 deletions
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6
fs/ext4/inode.c
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@@ -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);