Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e8f077c8 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Greg Kroah-Hartman
Browse files

sysfs: Use dentry_ops instead of directly playing with the dcache 



Calling d_drop unconditionally when a sysfs_dirent is deleted has
the potential to leak mounts, so instead implement dentry delete
and revalidate operations that cause sysfs dentries to be removed
at the appropriate time.

Acked-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Signed-off-by: default avatarEric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 28a027cf

fs/sysfs/dir.c

+46 −27
Original line number Diff line number Diff line
@@ -298,6 +298,46 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) 
		goto repeat;

}



static int sysfs_dentry_delete(struct dentry *dentry)

{

	struct sysfs_dirent *sd = dentry->d_fsdata;

	return !!(sd->s_flags & SYSFS_FLAG_REMOVED);

}



static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)

{

	struct sysfs_dirent *sd = dentry->d_fsdata;

	int is_dir;



	mutex_lock(&sysfs_mutex);



	/* The sysfs dirent has been deleted */

	if (sd->s_flags & SYSFS_FLAG_REMOVED)

		goto out_bad;



	mutex_unlock(&sysfs_mutex);

out_valid:

	return 1;

out_bad:

	/* Remove the dentry from the dcache hashes.

	 * If this is a deleted dentry we use d_drop instead of d_delete

	 * so sysfs doesn't need to cope with negative dentries.

	 */

	is_dir = (sysfs_type(sd) == SYSFS_DIR);

	mutex_unlock(&sysfs_mutex);

	if (is_dir) {

		/* If we have submounts we must allow the vfs caches

		 * to lie about the state of the filesystem to prevent

		 * leaks and other nasty things.

		 */

		if (have_submounts(dentry))

			goto out_valid;

		shrink_dcache_parent(dentry);

	}

	d_drop(dentry);

	return 0;

}



static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode)

{

	struct sysfs_dirent * sd = dentry->d_fsdata;
@@ -307,6 +347,8 @@ static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode) 
}



static const struct dentry_operations sysfs_dentry_ops = {

	.d_revalidate	= sysfs_dentry_revalidate,

	.d_delete	= sysfs_dentry_delete,

	.d_iput		= sysfs_dentry_iput,

};
@@ -527,44 +569,21 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) 
}



/**

 *	sysfs_drop_dentry - drop dentry for the specified sysfs_dirent

 *	sysfs_dec_nlink - Decrement link count for the specified sysfs_dirent

 *	@sd: target sysfs_dirent

 *

 *	Drop dentry for @sd.  @sd must have been unlinked from its

 *	Decrement nlink for @sd.  @sd must have been unlinked from its

 *	parent on entry to this function such that it can't be looked

 *	up anymore.

 */

static void sysfs_drop_dentry(struct sysfs_dirent *sd)

static void sysfs_dec_nlink(struct sysfs_dirent *sd)

{

	struct inode *inode;

	struct dentry *dentry;



	inode = ilookup(sysfs_sb, sd->s_ino);

	if (!inode)

		return;



	/* Drop any existing dentries associated with sd.

	 *

	 * For the dentry to be properly freed we need to grab a

	 * reference to the dentry under the dcache lock,  unhash it,

	 * and then put it.  The playing with the dentry count allows

	 * dput to immediately free the dentry  if it is not in use.

	 */

repeat:

	spin_lock(&dcache_lock);

	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {

		if (d_unhashed(dentry))

			continue;

		dget_locked(dentry);

		spin_lock(&dentry->d_lock);

		__d_drop(dentry);

		spin_unlock(&dentry->d_lock);

		spin_unlock(&dcache_lock);

		dput(dentry);

		goto repeat;

	}

	spin_unlock(&dcache_lock);



	/* adjust nlink and update timestamp */

	mutex_lock(&inode->i_mutex);
@@ -611,7 +630,7 @@ void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt) 
		acxt->removed = sd->s_sibling;

		sd->s_sibling = NULL;



		sysfs_drop_dentry(sd);

		sysfs_dec_nlink(sd);

		sysfs_deactivate(sd);

		unmap_bin_file(sd);

		sysfs_put(sd);