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Commit 23adbe12 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Linus Torvalds
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fs,userns: Change inode_capable to capable_wrt_inode_uidgid 



The kernel has no concept of capabilities with respect to inodes; inodes
exist independently of namespaces.  For example, inode_capable(inode,
CAP_LINUX_IMMUTABLE) would be nonsense.

This patch changes inode_capable to check for uid and gid mappings and
renames it to capable_wrt_inode_uidgid, which should make it more
obvious what it does.

Fixes CVE-2014-4014.

Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5b174fd6

fs/attr.c

+4 −4
Original line number Diff line number Diff line
@@ -50,14 +50,14 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr) 
	if ((ia_valid & ATTR_UID) &&

	    (!uid_eq(current_fsuid(), inode->i_uid) ||

	     !uid_eq(attr->ia_uid, inode->i_uid)) &&

	    !inode_capable(inode, CAP_CHOWN))

	    !capable_wrt_inode_uidgid(inode, CAP_CHOWN))

		return -EPERM;



	/* Make sure caller can chgrp. */

	if ((ia_valid & ATTR_GID) &&

	    (!uid_eq(current_fsuid(), inode->i_uid) ||

	    (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&

	    !inode_capable(inode, CAP_CHOWN))

	    !capable_wrt_inode_uidgid(inode, CAP_CHOWN))

		return -EPERM;



	/* Make sure a caller can chmod. */
@@ -67,7 +67,7 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr) 
		/* Also check the setgid bit! */

		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :

				inode->i_gid) &&

		    !inode_capable(inode, CAP_FSETID))

		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))

			attr->ia_mode &= ~S_ISGID;

	}
@@ -160,7 +160,7 @@ void setattr_copy(struct inode *inode, const struct iattr *attr) 
		umode_t mode = attr->ia_mode;



		if (!in_group_p(inode->i_gid) &&

		    !inode_capable(inode, CAP_FSETID))

		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))

			mode &= ~S_ISGID;

		inode->i_mode = mode;

	}

fs/inode.c

+7 −3
Original line number Diff line number Diff line
@@ -1839,14 +1839,18 @@ EXPORT_SYMBOL(inode_init_owner); 
 * inode_owner_or_capable - check current task permissions to inode

 * @inode: inode being checked

 *

 * Return true if current either has CAP_FOWNER to the inode, or

 * owns the file.

 * Return true if current either has CAP_FOWNER in a namespace with the

 * inode owner uid mapped, or owns the file.

 */

bool inode_owner_or_capable(const struct inode *inode)

{

	struct user_namespace *ns;



	if (uid_eq(current_fsuid(), inode->i_uid))

		return true;

	if (inode_capable(inode, CAP_FOWNER))



	ns = current_user_ns();

	if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))

		return true;

	return false;

}

fs/namei.c

+6 −5
Original line number Diff line number Diff line
@@ -332,10 +332,11 @@ int generic_permission(struct inode *inode, int mask) 


	if (S_ISDIR(inode->i_mode)) {

		/* DACs are overridable for directories */

		if (inode_capable(inode, CAP_DAC_OVERRIDE))

		if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))

			return 0;

		if (!(mask & MAY_WRITE))

			if (inode_capable(inode, CAP_DAC_READ_SEARCH))

			if (capable_wrt_inode_uidgid(inode,

						     CAP_DAC_READ_SEARCH))

				return 0;

		return -EACCES;

	}
@@ -345,7 +346,7 @@ int generic_permission(struct inode *inode, int mask) 
	 * at least one exec bit set.

	 */

	if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))

		if (inode_capable(inode, CAP_DAC_OVERRIDE))

		if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))

			return 0;



	/*
@@ -353,7 +354,7 @@ int generic_permission(struct inode *inode, int mask) 
	 */

	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;

	if (mask == MAY_READ)

		if (inode_capable(inode, CAP_DAC_READ_SEARCH))

		if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))

			return 0;



	return -EACCES;
@@ -2379,7 +2380,7 @@ static inline int check_sticky(struct inode *dir, struct inode *inode) 
		return 0;

	if (uid_eq(dir->i_uid, fsuid))

		return 0;

	return !inode_capable(inode, CAP_FOWNER);

	return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);

}



/*

fs/xfs/xfs_ioctl.c

+1 −1
Original line number Diff line number Diff line
@@ -1215,7 +1215,7 @@ xfs_ioctl_setattr( 
		 * cleared upon successful return from chown()

		 */

		if ((ip->i_d.di_mode & (S_ISUID|S_ISGID)) &&

		    !inode_capable(VFS_I(ip), CAP_FSETID))

		    !capable_wrt_inode_uidgid(VFS_I(ip), CAP_FSETID))

			ip->i_d.di_mode &= ~(S_ISUID|S_ISGID);



		/*

include/linux/capability.h

+1 −1
Original line number Diff line number Diff line
@@ -210,7 +210,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t, 
				      struct user_namespace *ns, int cap);

extern bool capable(int cap);

extern bool ns_capable(struct user_namespace *ns, int cap);

extern bool inode_capable(const struct inode *inode, int cap);

extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);

extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);



/* audit system wants to get cap info from files as well */