genetlink: no longer support using static family IDs

Static family IDs have never really been used, the only
use case was the workaround I introduced for those users
that assumed their family ID was also their multicast
group ID.

Additionally, because static family IDs would never be
reserved by the generic netlink code, using a relatively
low ID would only work for built-in families that can be
registered immediately after generic netlink is started,
which is basically only the control family (apart from
the workaround code, which I also had to add code for so
it would reserve those IDs)

Thus, anything other than GENL_ID_GENERATE is flawed and
luckily not used except in the cases I mentioned. Move
those workarounds into a few lines of code, and then get
rid of GENL_ID_GENERATE entirely, making it more robust.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 15 deletions

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 01291b7a27bb..f19ec969edee 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -349,8 +349,6 @@ static int genl_validate_ops(const struct genl_family *family)
  *
  * Registers the specified family after validating it first. Only one
  * family may be registered with the same family name or identifier.
- * The family id may equal GENL_ID_GENERATE causing an unique id to
- * be automatically generated and assigned.
  *
  * The family's ops array must already be assigned, you can use the
  * genl_register_family_with_ops() helper function.
@@ -359,13 +357,7 @@ static int genl_validate_ops(const struct genl_family *family)
  */
 int __genl_register_family(struct genl_family *family)
 {
-	int err = -EINVAL, i;
-
-	if (family->id && family->id < GENL_MIN_ID)
-		goto errout;
-
-	if (family->id > GENL_MAX_ID)
-		goto errout;
+	int err, i;
 
 	err = genl_validate_ops(family);
 	if (err)
@@ -378,8 +370,27 @@ int __genl_register_family(struct genl_family *family)
 		goto errout_locked;
 	}
 
-	if (family->id == GENL_ID_GENERATE) {
-		u16 newid = genl_generate_id();
+	if (family == &genl_ctrl) {
+		family->id = GENL_ID_CTRL;
+	} else {
+		u16 newid;
+
+		/* this should be left zero in the struct */
+		WARN_ON(family->id);
+
+		/*
+		 * Sadly, a few cases need to be special-cased
+		 * due to them having previously abused the API
+		 * and having used their family ID also as their
+		 * multicast group ID, so we use reserved IDs
+		 * for both to be sure we can do that mapping.
+		 */
+		if (strcmp(family->name, "pmcraid") == 0)
+			newid = GENL_ID_PMCRAID;
+		else if (strcmp(family->name, "VFS_DQUOT") == 0)
+			newid = GENL_ID_VFS_DQUOT;
+		else
+			newid = genl_generate_id();
 
 		if (!newid) {
 			err = -ENOMEM;
@@ -387,9 +398,6 @@ int __genl_register_family(struct genl_family *family)
 		}
 
 		family->id = newid;
-	} else if (genl_family_find_byid(family->id)) {
-		err = -EEXIST;
-		goto errout_locked;
 	}
 
 	if (family->maxattr && !family->parallel_ops) {
@@ -419,7 +427,6 @@ int __genl_register_family(struct genl_family *family)
 
 errout_locked:
 	genl_unlock_all();
-errout:
 	return err;
 }
 EXPORT_SYMBOL(__genl_register_family);