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authorEric W. Biederman <ebiederm@xmission.com>2016-06-30 16:31:01 -0500
committerEric W. Biederman <ebiederm@xmission.com>2016-07-05 15:12:05 -0500
commitd49d37624a1931c2f3b5d0cbe95bd5181cbdc279 (patch)
treef81e4129a5a393df64b6b674ed9aae83a404f707
parent036d523641c66bef713042894a17f4335f199e49 (diff)
downloadlinux-d49d37624a1931c2f3b5d0cbe95bd5181cbdc279.tar.bz2
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: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r--fs/quota/dquot.c3
-rw-r--r--fs/quota/quota.c12
-rw-r--r--include/linux/quota.h10
3 files changed, 19 insertions, 6 deletions
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index ff21980d0119..74706b6aa747 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -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:
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 0f10ee9892ce..73f6f4cf0a21 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -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)
diff --git a/include/linux/quota.h b/include/linux/quota.h
index 9dfb6bce8c9e..1db16ee39b31 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -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;