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>
diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 0f10ee9..73f6f4c 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -211,7 +211,7 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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)