Commit d49d3762 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

quota: Ensure qids map to the filesystem 



Introduce the helper qid_has_mapping and use it to ensure that the
quota system only considers qids that map to the filesystems
s_user_ns.

In practice for quota supporting filesystems today this is the exact
same check as qid_valid.  As only 0xffffffff aka (qid_t)-1 does not
map into init_user_ns.

Replace the qid_valid calls with qid_has_mapping as values come in
from userspace.  This is harmless today and it prepares the quota
system to work on filesystems with quotas but mounted by unprivileged
users.

Call qid_has_mapping from dqget.  This ensures the passed in qid has a
prepresentation on the underlying filesystem.  Previously this was
unnecessary as filesystesm never had qids that could not map.  With
the introduction of filesystems outside of s_user_ns this will not
remain true.

All of this ensures the quota code never has to deal with qids that
don't map to the underlying filesystem.

Cc: Jan Kara <jack@suse.cz>
Acked-by: default avatarSeth Forshee <seth.forshee@canonical.com>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 036d5236

fs/quota/dquot.c

+3 −0
Original line number Diff line number Diff line
@@ -841,6 +841,9 @@ struct dquot *dqget(struct super_block *sb, struct kqid qid) 
	unsigned int hashent = hashfn(sb, qid);

	struct dquot *dquot, *empty = NULL;



	if (!qid_has_mapping(sb->s_user_ns, qid))

		return ERR_PTR(-EINVAL);



        if (!sb_has_quota_active(sb, qid.type))

		return ERR_PTR(-ESRCH);

we_slept:

fs/quota/quota.c

+6 −6
Original line number Diff line number Diff line
@@ -211,7 +211,7 @@ static int quota_getquota(struct super_block *sb, int type, qid_t id, 
	if (!sb->s_qcop->get_dqblk)

		return -ENOSYS;

	qid = make_kqid(current_user_ns(), type, id);

	if (!qid_valid(qid))

	if (!qid_has_mapping(sb->s_user_ns, qid))

		return -EINVAL;

	ret = sb->s_qcop->get_dqblk(sb, qid, &fdq);

	if (ret)
@@ -237,7 +237,7 @@ static int quota_getnextquota(struct super_block *sb, int type, qid_t id, 
	if (!sb->s_qcop->get_nextdqblk)

		return -ENOSYS;

	qid = make_kqid(current_user_ns(), type, id);

	if (!qid_valid(qid))

	if (!qid_has_mapping(sb->s_user_ns, qid))

		return -EINVAL;

	ret = sb->s_qcop->get_nextdqblk(sb, &qid, &fdq);

	if (ret)
@@ -288,7 +288,7 @@ static int quota_setquota(struct super_block *sb, int type, qid_t id, 
	if (!sb->s_qcop->set_dqblk)

		return -ENOSYS;

	qid = make_kqid(current_user_ns(), type, id);

	if (!qid_valid(qid))

	if (!qid_has_mapping(sb->s_user_ns, qid))

		return -EINVAL;

	copy_from_if_dqblk(&fdq, &idq);

	return sb->s_qcop->set_dqblk(sb, qid, &fdq);
@@ -581,7 +581,7 @@ static int quota_setxquota(struct super_block *sb, int type, qid_t id, 
	if (!sb->s_qcop->set_dqblk)

		return -ENOSYS;

	qid = make_kqid(current_user_ns(), type, id);

	if (!qid_valid(qid))

	if (!qid_has_mapping(sb->s_user_ns, qid))

		return -EINVAL;

	/* Are we actually setting timer / warning limits for all users? */

	if (from_kqid(&init_user_ns, qid) == 0 &&
@@ -642,7 +642,7 @@ static int quota_getxquota(struct super_block *sb, int type, qid_t id, 
	if (!sb->s_qcop->get_dqblk)

		return -ENOSYS;

	qid = make_kqid(current_user_ns(), type, id);

	if (!qid_valid(qid))

	if (!qid_has_mapping(sb->s_user_ns, qid))

		return -EINVAL;

	ret = sb->s_qcop->get_dqblk(sb, qid, &qdq);

	if (ret)
@@ -669,7 +669,7 @@ static int quota_getnextxquota(struct super_block *sb, int type, qid_t id, 
	if (!sb->s_qcop->get_nextdqblk)

		return -ENOSYS;

	qid = make_kqid(current_user_ns(), type, id);

	if (!qid_valid(qid))

	if (!qid_has_mapping(sb->s_user_ns, qid))

		return -EINVAL;

	ret = sb->s_qcop->get_nextdqblk(sb, &qid, &qdq);

	if (ret)

include/linux/quota.h

+10 −0
Original line number Diff line number Diff line
@@ -179,6 +179,16 @@ static inline struct kqid make_kqid_projid(kprojid_t projid) 
	return kqid;

}



/**

 *	qid_has_mapping - Report if a qid maps into a user namespace.

 *	@ns:  The user namespace to see if a value maps into.

 *	@qid: The kernel internal quota identifier to test.

 */

static inline bool qid_has_mapping(struct user_namespace *ns, struct kqid qid)

{

	return from_kqid(ns, qid) != (qid_t) -1;

}





extern spinlock_t dq_data_lock;

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