quota: simplify permission checking

Stop having complicated different routines for checking permissions for
XQM vs "VFS" quotas.  Instead do the checks for having sb->s_qcop and
a valid type directly in do_quotactl, and munge the *quotactl_valid functions
into a check_quotactl_permission helper that only checks for permissions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 31 insertions, 61 deletions

diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 9fde5cd84f8d..d0efe302b1c1 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -21,69 +21,30 @@
 #include <net/netlink.h>
 #include <net/genetlink.h>
 
-/* Check validity of generic quotactl commands */
-static int generic_quotactl_valid(struct super_block *sb, int type, int cmd,
-                                  qid_t id)
+static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
+                                     qid_t id)
 {
-        if (type >= MAXQUOTAS)
-                return -EINVAL;
-        if (!sb && cmd != Q_SYNC)
-                return -ENODEV;
-        /* Is operation supported? */
-        if (sb && !sb->s_qcop)
-                return -ENOSYS;
-
-        /* Check privileges */
-        if (cmd == Q_GETQUOTA) {
-                if (((type == USRQUOTA && current_euid() != id) ||
-                     (type == GRPQUOTA && !in_egroup_p(id))) &&
-                    !capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-        }
-        else if (cmd != Q_GETFMT && cmd != Q_SYNC && cmd != Q_GETINFO)
-                if (!capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-
-        return 0;
-}
-
-/* Check validity of XFS Quota Manager commands */
-static int xqm_quotactl_valid(struct super_block *sb, int type, int cmd,
-                              qid_t id)
-{
-        if (type >= XQM_MAXQUOTAS)
-                return -EINVAL;
-        if (!sb)
-                return -ENODEV;
-        if (!sb->s_qcop)
-                return -ENOSYS;
-
-        /* Check privileges */
-        if (cmd == Q_XGETQUOTA) {
-                if (((type == XQM_USRQUOTA && current_euid() != id) ||
-                     (type == XQM_GRPQUOTA && !in_egroup_p(id))) &&
-                     !capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-        } else if (cmd != Q_XGETQSTAT && cmd != Q_XQUOTASYNC) {
+        switch (cmd) {
+        /* these commands do not require any special privilegues */
+        case Q_GETFMT:
+        case Q_SYNC:
+        case Q_GETINFO:
+        case Q_XGETQSTAT:
+        case Q_XQUOTASYNC:
+                break;
+        /* allow to query information for dquots we "own" */
+        case Q_GETQUOTA:
+        case Q_XGETQUOTA:
+                if ((type == USRQUOTA && current_euid() == id) ||
+                    (type == GRPQUOTA && in_egroup_p(id)))
+                        break;
+                /*FALLTHROUGH*/
+        default:
                 if (!capable(CAP_SYS_ADMIN))
                         return -EPERM;
         }
 
-        return 0;
-}
-
-static int check_quotactl_valid(struct super_block *sb, int type, int cmd,
-                                qid_t id)
-{
-        int error;
-
-        if (XQM_COMMAND(cmd))
-                error = xqm_quotactl_valid(sb, type, cmd, id);
-        else
-                error = generic_quotactl_valid(sb, type, cmd, id);
-        if (!error)
-                error = security_quotactl(cmd, type, id, sb);
-        return error;
+        return security_quotactl(cmd, type, id, sb);
 }
 
 #ifdef CONFIG_QUOTA
@@ -313,6 +274,17 @@ static int quota_getxquota(struct super_block *sb, int type, qid_t id,
 static int do_quotactl(struct super_block *sb, int type, int cmd, qid_t id,
                        void __user *addr)
 {
+        int ret;
+
+        if (type >= (XQM_COMMAND(cmd) ? XQM_MAXQUOTAS : MAXQUOTAS))
+                return -EINVAL;
+        if (!sb->s_qcop)
+                return -ENOSYS;
+
+        ret = check_quotactl_permission(sb, type, cmd, id);
+        if (ret < 0)
+                return ret;
+
         switch (cmd) {
         case Q_QUOTAON:
                 return quota_quotaon(sb, type, cmd, id, addr);
@@ -413,9 +385,7 @@ SYSCALL_DEFINE4(quotactl, unsigned int, cmd, const char __user *, special,
         if (IS_ERR(sb))
                 return PTR_ERR(sb);
 
-        ret = check_quotactl_valid(sb, type, cmds, id);
-        if (ret >= 0)
-                ret = do_quotactl(sb, type, cmds, id, addr);
+        ret = do_quotactl(sb, type, cmds, id, addr);
 
         drop_super(sb);
         return ret;