Commit ae54870a authored by Jan Kara's avatar Jan Kara
Browse files

ext3: Fix lock inversion in ext3_symlink() 



ext3_symlink() cannot call __page_symlink() with transaction open.
__page_symlink() calls ext3_write_begin() which gets page lock which ranks
above transaction start (thus lock ordering is violated) and and also
ext3_write_begin() waits for a transaction commit when we run out of space
which never happens if we hold transaction open.

Fix the problem by stopping a transaction before calling __page_symlink()
(we have to be careful and put inode to orphan list so that it gets deleted
in case of crash) and starting another one after __page_symlink() returns
for addition of symlink into a directory.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent fafc9929

fs/ext3/namei.c

+56 −11
Original line number Diff line number Diff line
@@ -2189,6 +2189,7 @@ static int ext3_symlink (struct inode * dir, 
	handle_t *handle;

	struct inode * inode;

	int l, err, retries = 0;

	int credits;



	l = strlen(symname)+1;

	if (l > dir->i_sb->s_blocksize)
@@ -2196,10 +2197,26 @@ static int ext3_symlink (struct inode * dir, 


	dquot_initialize(dir);



	if (l > EXT3_N_BLOCKS * 4) {

		/*

		 * For non-fast symlinks, we just allocate inode and put it on

		 * orphan list in the first transaction => we need bitmap,

		 * group descriptor, sb, inode block, quota blocks.

		 */

		credits = 4 + EXT3_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);

	} else {

		/*

		 * Fast symlink. We have to add entry to directory

		 * (EXT3_DATA_TRANS_BLOCKS + EXT3_INDEX_EXTRA_TRANS_BLOCKS),

		 * allocate new inode (bitmap, group descriptor, inode block,

		 * quota blocks, sb is already counted in previous macros).

		 */

		credits = EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +

			  EXT3_INDEX_EXTRA_TRANS_BLOCKS + 3 +

			  EXT3_MAXQUOTAS_INIT_BLOCKS(dir->i_sb);

	}

retry:

	handle = ext3_journal_start(dir, EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +

					EXT3_INDEX_EXTRA_TRANS_BLOCKS + 5 +

					EXT3_MAXQUOTAS_INIT_BLOCKS(dir->i_sb));

	handle = ext3_journal_start(dir, credits);

	if (IS_ERR(handle))

		return PTR_ERR(handle);
@@ -2211,21 +2228,45 @@ retry: 
	if (IS_ERR(inode))

		goto out_stop;



	if (l > sizeof (EXT3_I(inode)->i_data)) {

	if (l > EXT3_N_BLOCKS * 4) {

		inode->i_op = &ext3_symlink_inode_operations;

		ext3_set_aops(inode);

		/*

		 * page_symlink() calls into ext3_prepare/commit_write.

		 * We have a transaction open.  All is sweetness.  It also sets

		 * i_size in generic_commit_write().

		 * We cannot call page_symlink() with transaction started

		 * because it calls into ext3_write_begin() which acquires page

		 * lock which ranks below transaction start (and it can also

		 * wait for journal commit if we are running out of space). So

		 * we have to stop transaction now and restart it when symlink

		 * contents is written. 

		 *

		 * To keep fs consistent in case of crash, we have to put inode

		 * to orphan list in the mean time.

		 */

		drop_nlink(inode);

		err = ext3_orphan_add(handle, inode);

		ext3_journal_stop(handle);

		if (err)

			goto err_drop_inode;

		err = __page_symlink(inode, symname, l, 1);

		if (err)

			goto err_drop_inode;

		/*

		 * Now inode is being linked into dir (EXT3_DATA_TRANS_BLOCKS

		 * + EXT3_INDEX_EXTRA_TRANS_BLOCKS), inode is also modified

		 */

		handle = ext3_journal_start(dir,

				EXT3_DATA_TRANS_BLOCKS(dir->i_sb) +

				EXT3_INDEX_EXTRA_TRANS_BLOCKS + 1);

		if (IS_ERR(handle)) {

			err = PTR_ERR(handle);

			goto err_drop_inode;

		}

		inc_nlink(inode);

		err = ext3_orphan_del(handle, inode);

		if (err) {

			ext3_journal_stop(handle);

			drop_nlink(inode);

			unlock_new_inode(inode);

			ext3_mark_inode_dirty(handle, inode);

			iput (inode);

			goto out_stop;

			goto err_drop_inode;

		}

	} else {

		inode->i_op = &ext3_fast_symlink_inode_operations;
@@ -2239,6 +2280,10 @@ out_stop: 
	if (err == -ENOSPC && ext3_should_retry_alloc(dir->i_sb, &retries))

		goto retry;

	return err;

err_drop_inode:

	unlock_new_inode(inode);

	iput (inode);

	return err;

}



static int ext3_link (struct dentry * old_dentry,

CRA Git | Maintained and supported by SUSTech CRA and CCSE