Commit 057f6c01 authored by James Morris's avatar James Morris Committed by Greg Kroah-Hartman
Browse files

security: prevent permission checking of file removal via sysfs_remove_group() 



Prevent permission checking from being performed when the kernel wants to
unconditionally remove a sysfs group, by introducing an kernel-only variant
of lookup_one_len(), lookup_one_len_kern().

Additionally, as sysfs_remove_group() does not check the return value of
the lookup before using it, a BUG_ON has been added to pinpoint the cause
of any problems potentially caused by this (and as a form of annotation).

Signed-off-by: default avatarJames Morris <jmorris@namei.org>
Cc: Nagendra Singh Tomar <nagendra_tomar@adaptec.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 523ded71

fs/namei.c

+52 −20
Original line number Diff line number Diff line
@@ -1243,22 +1243,13 @@ int __user_path_lookup_open(const char __user *name, unsigned int lookup_flags, 
	return err;

}



/*

 * Restricted form of lookup. Doesn't follow links, single-component only,

 * needs parent already locked. Doesn't follow mounts.

 * SMP-safe.

 */

static struct dentry * __lookup_hash(struct qstr *name, struct dentry * base, struct nameidata *nd)

static inline struct dentry *__lookup_hash_kern(struct qstr *name, struct dentry *base, struct nameidata *nd)

{

	struct dentry *dentry;

	struct inode *inode;

	int err;



	inode = base->d_inode;

	err = permission(inode, MAY_EXEC, nd);

	dentry = ERR_PTR(err);

	if (err)

		goto out;



	/*

	 * See if the low-level filesystem might want
@@ -1287,35 +1278,76 @@ out: 
	return dentry;

}



/*

 * Restricted form of lookup. Doesn't follow links, single-component only,

 * needs parent already locked. Doesn't follow mounts.

 * SMP-safe.

 */

static inline struct dentry * __lookup_hash(struct qstr *name, struct dentry *base, struct nameidata *nd)

{

	struct dentry *dentry;

	struct inode *inode;

	int err;



	inode = base->d_inode;



	err = permission(inode, MAY_EXEC, nd);

	dentry = ERR_PTR(err);

	if (err)

		goto out;



	dentry = __lookup_hash_kern(name, base, nd);

out:

	return dentry;

}



static struct dentry *lookup_hash(struct nameidata *nd)

{

	return __lookup_hash(&nd->last, nd->dentry, nd);

}



/* SMP-safe */

struct dentry * lookup_one_len(const char * name, struct dentry * base, int len)

static inline int __lookup_one_len(const char *name, struct qstr *this, struct dentry *base, int len)

{

	unsigned long hash;

	struct qstr this;

	unsigned int c;



	this.name = name;

	this.len = len;

	this->name = name;

	this->len = len;

	if (!len)

		goto access;

		return -EACCES;



	hash = init_name_hash();

	while (len--) {

		c = *(const unsigned char *)name++;

		if (c == '/' || c == '\0')

			goto access;

			return -EACCES;

		hash = partial_name_hash(c, hash);

	}

	this.hash = end_name_hash(hash);

	this->hash = end_name_hash(hash);

	return 0;

}



struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)

{

	int err;

	struct qstr this;



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

	if (err)

		return ERR_PTR(err);

	return __lookup_hash(&this, base, NULL);

access:

	return ERR_PTR(-EACCES);

}



struct dentry *lookup_one_len_kern(const char *name, struct dentry *base, int len)

{

	int err;

	struct qstr this;



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

	if (err)

		return ERR_PTR(err);

	return __lookup_hash_kern(&this, base, NULL);

}



/*

fs/sysfs/group.c

+4 −2
Original line number Diff line number Diff line
@@ -70,9 +70,11 @@ void sysfs_remove_group(struct kobject * kobj, 
{

	struct dentry * dir;



	if (grp->name)

		dir = lookup_one_len(grp->name, kobj->dentry,

	if (grp->name) {

		dir = lookup_one_len_kern(grp->name, kobj->dentry,

				strlen(grp->name));

		BUG_ON(IS_ERR(dir));

	}

	else

		dir = dget(kobj->dentry);

include/linux/namei.h

+1 −0
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ extern struct file *nameidata_to_filp(struct nameidata *nd, int flags); 
extern void release_open_intent(struct nameidata *);



extern struct dentry * lookup_one_len(const char *, struct dentry *, int);

extern struct dentry *lookup_one_len_kern(const char *, struct dentry *, int);



extern int follow_down(struct vfsmount **, struct dentry **);

extern int follow_up(struct vfsmount **, struct dentry **);

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