ipc,sysv: return -EINVAL upon incorrect id/seqnum

In ipc_obtain_object_check we return -EIDRM when a bogus sequence number
is detected via ipc_checkid, while the ipc manpages state the following
return codes for such errors:

   EIDRM  <ID> points to a removed identifier.
   EINVAL Invalid <ID> value, or unaligned, etc.

EIDRM should only be returned upon a RMID call (->deleted check), and thus
return EINVAL for wrong seq.  This difference in semantics has also caused
real bugs, ie: https://bugzilla.redhat.com/show_bug.cgi?id=246509



Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/util.c

@@ -622,7 +622,7 @@ struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 		goto out;
 
 	if (ipc_checkid(out, id))
-		return ERR_PTR(-EIDRM);
+		return ERR_PTR(-EINVAL);
 out:
 	return out;
 }