ext4: fix a bug accessing freed memory in ext4_abort

Vegard Nossum reported a bug which accesses freed memory (found via
kmemcheck).  When journal has been aborted, ext4_put_super() calls
ext4_abort() after freeing the journal_t object, and then ext4_abort()
accesses it.  This patch fix it.
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/super.c

@@ -333,7 +333,8 @@ void ext4_abort(struct super_block *sb, const char *function,
 	EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
 	sb->s_flags |= MS_RDONLY;
 	EXT4_SB(sb)->s_mount_opt |= EXT4_MOUNT_ABORT;
-	jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
+	if (EXT4_SB(sb)->s_journal)
+		jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
 }
 
 void ext4_warning(struct super_block *sb, const char *function,
@@ -442,14 +443,16 @@ static void ext4_put_super(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_super_block *es = sbi->s_es;
-	int i;
+	int i, err;
 
 	ext4_mb_release(sb);
 	ext4_ext_release(sb);
 	ext4_xattr_put_super(sb);
-	if (jbd2_journal_destroy(sbi->s_journal) < 0)
-		ext4_abort(sb, __func__, "Couldn't clean up the journal");
+	err = jbd2_journal_destroy(sbi->s_journal);
 	sbi->s_journal = NULL;
+	if (err < 0)
+		ext4_abort(sb, __func__, "Couldn't clean up the journal");
+
 	if (!(sb->s_flags & MS_RDONLY)) {
 		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
 		es->s_state = cpu_to_le16(sbi->s_mount_state);