Ocfs2 devel - Apr 2016 - [PATCH 1/2] quota: Handle Q_GETNEXTQUOTA when quota is disabled

Currently we oopsed when Q_GETNEXTQUOTA got called when quota was
disabled. Properly check whether quota is enabled for the filesystem
before calling into quota format handler.

Reported-by: Ted Tso <tytso at mit.edu>
Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/quota/dquot.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

I have queue this fix for the bug Ted reported and will push it to Linus soon.

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index ba827daea5a0..ff21980d0119 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -2047,11 +2047,20 @@ int dquot_get_next_id(struct super_block *sb, struct
kqid *qid)
 	struct quota_info *dqopt = sb_dqopt(sb);
 	int err;
 
-	if (!dqopt->ops[qid->type]->get_next_id)
-		return -ENOSYS;
+	mutex_lock(&dqopt->dqonoff_mutex);
+	if (!sb_has_quota_active(sb, qid->type)) {
+		err = -ESRCH;
+		goto out;
+	}
+	if (!dqopt->ops[qid->type]->get_next_id) {
+		err = -ENOSYS;
+		goto out;
+	}
 	mutex_lock(&dqopt->dqio_mutex);
 	err = dqopt->ops[qid->type]->get_next_id(sb, qid);
 	mutex_unlock(&dqopt->dqio_mutex);
+out:
+	mutex_unlock(&dqopt->dqonoff_mutex);
 
 	return err;
 }
-- 
2.6.2

When Q_GETNEXTQUOTA was called for filesystem with quotas disabled
ocfs2_get_next_id() oopses. Fix the problem by checking early whether
the filesystem has quotas enabled.

Signed-off-by: Jan Kara <jack at suse.cz>
---
 fs/ocfs2/quota_global.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/quota_global.c b/fs/ocfs2/quota_global.c
index 3892f3c079ca..ab6a6cdcf91c 100644
--- a/fs/ocfs2/quota_global.c
+++ b/fs/ocfs2/quota_global.c
@@ -867,6 +867,10 @@ static int ocfs2_get_next_id(struct super_block *sb, struct
kqid *qid)
 	int status = 0;
 
 	trace_ocfs2_get_next_id(from_kqid(&init_user_ns, *qid), type);
+	if (!sb_has_quota_loaded(sb, type)) {
+		status = -ESRCH;
+		goto out;
+	}
 	status = ocfs2_lock_global_qf(info, 0);
 	if (status < 0)
 		goto out;
@@ -878,8 +882,11 @@ static int ocfs2_get_next_id(struct super_block *sb, struct
kqid *qid)
 out_global:
 	ocfs2_unlock_global_qf(info, 0);
 out:
-	/* Avoid logging ENOENT since it just means there isn't next ID */
-	if (status && status != -ENOENT)
+	/*
+	 * Avoid logging ENOENT since it just means there isn't next ID and
+	 * ESRCH which means quota isn't enabled for the filesystem.
+	 */
+	if (status && status != -ENOENT && status != -ESRCH)
 		mlog_errno(status);
 	return status;
 }
-- 
2.6.2

On Tue, Mar 29, 2016 at 06:11:43PM +0200, Jan Kara
wrote:
> Currently we oopsed when Q_GETNEXTQUOTA got called when quota was
> disabled. Properly check whether quota is enabled for the filesystem
> before calling into quota format handler.
> 
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index ba827daea5a0..ff21980d0119 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -2047,11 +2047,20 @@ int dquot_get_next_id(struct super_block *sb,
struct kqid *qid)
>  	struct quota_info *dqopt = sb_dqopt(sb);
>  	int err;
>  
> -	if (!dqopt->ops[qid->type]->get_next_id)
> -		return -ENOSYS;
> +	mutex_lock(&dqopt->dqonoff_mutex);
> +	if (!sb_has_quota_active(sb, qid->type)) {
> +		err = -ESRCH;
> +		goto out;
> +	}
> +	if (!dqopt->ops[qid->type]->get_next_id) {
> +		err = -ENOSYS;
> +		goto out;
> +	}
Don't you also have to test if dqopt->ops[qid->type] is NULL?  e.g.,
if the quota inode hasn't been loaded for that quota type?

Also, I notice you have this queued on the for_next branch and not the
for_linus branch.  I was hoping you could push this to Linus sooner
than the next merge cycle, since this is (a) making my testing hard,
and (b) it makes it easy for an attacker to crash the system.  For
similar reasons, perhaps this should have a cc: stable at vger.kernel.org
tag?

Thanks,

					- Ted