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>

diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index 9fde5cd..d0efe30 100644 (file)
--- 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;