Commit 2f9092e1 authored by David Woodhouse's avatar David Woodhouse Committed by Al Viro
Browse files

Fix i_mutex vs. readdir handling in nfsd 



Commit 14f7dd63 ("Copy XFS readdir hack into nfsd code") introduced a
bug to generic code which had been extant for a long time in the XFS
version -- it started to call through into lookup_one_len() and hence
into the file systems' ->lookup() methods without i_mutex held on the
directory.

This patch fixes it by locking the directory's i_mutex again before
calling the filldir functions. The original deadlocks which commit
14f7dd63 was designed to avoid are still avoided, because they were due
to fs-internal locking, not i_mutex.

While we're at it, fix the return type of nfsd_buffered_readdir() which
should be a __be32 not an int -- it's an NFS errno, not a Linux errno.
And return nfserrno(-ENOMEM) when allocation fails, not just -ENOMEM.
Sparse would have caught that, if it wasn't so busy bitching about
__cold__.

Commit 05f4f678 ("nfsd4: don't do lookup within readdir in recovery
code") introduced a similar problem with calling lookup_one_len()
without i_mutex, which this patch also addresses. To fix that, it was
necessary to fix the called functions so that they expect i_mutex to be
held; that part was done by J. Bruce Fields.

Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
Umm-I-can-live-with-that-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Reported-by: default avatarJ. R. Okajima <hooanon05@yahoo.co.jp>
Tested-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
LKML-Reference: <8036.1237474444@jrobl>
Cc: stable@kernel.org
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 1ba0c7db

fs/namei.c

+2 −0
Original line number Diff line number Diff line
@@ -1248,6 +1248,8 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) 
	int err;

	struct qstr this;



	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));



	err = __lookup_one_len(name, &this, base, len);

	if (err)

		return ERR_PTR(err);

fs/nfsd/nfs4recover.c

+9 −37
Original line number Diff line number Diff line
@@ -229,21 +229,23 @@ nfsd4_list_rec_dir(struct dentry *dir, recdir_func *f) 
		goto out;

	status = vfs_readdir(filp, nfsd4_build_namelist, &names);

	fput(filp);

	mutex_lock(&dir->d_inode->i_mutex);

	while (!list_empty(&names)) {

		entry = list_entry(names.next, struct name_list, list);



		dentry = lookup_one_len(entry->name, dir, HEXDIR_LEN-1);

		if (IS_ERR(dentry)) {

			status = PTR_ERR(dentry);

			goto out;

			break;

		}

		status = f(dir, dentry);

		dput(dentry);

		if (status)

			goto out;

			break;

		list_del(&entry->list);

		kfree(entry);

	}

	mutex_unlock(&dir->d_inode->i_mutex);

out:

	while (!list_empty(&names)) {

		entry = list_entry(names.next, struct name_list, list);
@@ -254,36 +256,6 @@ out: 
	return status;

}



static int

nfsd4_remove_clid_file(struct dentry *dir, struct dentry *dentry)

{

	int status;



	if (!S_ISREG(dir->d_inode->i_mode)) {

		printk("nfsd4: non-file found in client recovery directory\n");

		return -EINVAL;

	}

	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);

	status = vfs_unlink(dir->d_inode, dentry);

	mutex_unlock(&dir->d_inode->i_mutex);

	return status;

}



static int

nfsd4_clear_clid_dir(struct dentry *dir, struct dentry *dentry)

{

	int status;



	/* For now this directory should already be empty, but we empty it of

	 * any regular files anyway, just in case the directory was created by

	 * a kernel from the future.... */

	nfsd4_list_rec_dir(dentry, nfsd4_remove_clid_file);

	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);

	status = vfs_rmdir(dir->d_inode, dentry);

	mutex_unlock(&dir->d_inode->i_mutex);

	return status;

}



static int

nfsd4_unlink_clid_dir(char *name, int namlen)

{
@@ -294,18 +266,18 @@ nfsd4_unlink_clid_dir(char *name, int namlen) 


	mutex_lock(&rec_dir.dentry->d_inode->i_mutex);

	dentry = lookup_one_len(name, rec_dir.dentry, namlen);

	mutex_unlock(&rec_dir.dentry->d_inode->i_mutex);

	if (IS_ERR(dentry)) {

		status = PTR_ERR(dentry);

		return status;

		goto out_unlock;

	}

	status = -ENOENT;

	if (!dentry->d_inode)

		goto out;



	status = nfsd4_clear_clid_dir(rec_dir.dentry, dentry);

	status = vfs_rmdir(rec_dir.dentry->d_inode, dentry);

out:

	dput(dentry);

out_unlock:

	mutex_unlock(&rec_dir.dentry->d_inode->i_mutex);

	return status;

}
@@ -348,7 +320,7 @@ purge_old(struct dentry *parent, struct dentry *child) 
	if (nfs4_has_reclaimed_state(child->d_name.name, false))

		return 0;



	status = nfsd4_clear_clid_dir(parent, child);

	status = vfs_rmdir(parent->d_inode, child);

	if (status)

		printk("failed to remove client recovery directory %s\n",

				child->d_name.name);

fs/nfsd/vfs.c

+19 −6
Original line number Diff line number Diff line
@@ -1890,7 +1890,7 @@ static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen, 
	return 0;

}



static int nfsd_buffered_readdir(struct file *file, filldir_t func,

static __be32 nfsd_buffered_readdir(struct file *file, filldir_t func,

				    struct readdir_cd *cdp, loff_t *offsetp)

{

	struct readdir_data buf;
@@ -1901,11 +1901,12 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func, 


	buf.dirent = (void *)__get_free_page(GFP_KERNEL);

	if (!buf.dirent)

		return -ENOMEM;

		return nfserrno(-ENOMEM);



	offset = *offsetp;



	while (1) {

		struct inode *dir_inode = file->f_path.dentry->d_inode;

		unsigned int reclen;



		cdp->err = nfserr_eof; /* will be cleared on successful read */
@@ -1924,26 +1925,38 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func, 
		if (!size)

			break;



		/*

		 * Various filldir functions may end up calling back into

		 * lookup_one_len() and the file system's ->lookup() method.

		 * These expect i_mutex to be held, as it would within readdir.

		 */

		host_err = mutex_lock_killable(&dir_inode->i_mutex);

		if (host_err)

			break;



		de = (struct buffered_dirent *)buf.dirent;

		while (size > 0) {

			offset = de->offset;



			if (func(cdp, de->name, de->namlen, de->offset,

				 de->ino, de->d_type))

				goto done;

				break;



			if (cdp->err != nfs_ok)

				goto done;

				break;



			reclen = ALIGN(sizeof(*de) + de->namlen,

				       sizeof(u64));

			size -= reclen;

			de = (struct buffered_dirent *)((char *)de + reclen);

		}

		mutex_unlock(&dir_inode->i_mutex);

		if (size > 0) /* We bailed out early */

			break;



		offset = vfs_llseek(file, 0, SEEK_CUR);

	}



 done:

	free_page((unsigned long)(buf.dirent));



	if (host_err)

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