1 files changed, 73 insertions, 36 deletions

diff --git a/ipc/util.c b/ipc/util.c
index cfa0045e748d..05cb9de66735 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -64,6 +64,7 @@
 #include <linux/memory.h>
 #include <linux/ipc_namespace.h>
 #include <linux/rhashtable.h>
+#include <linux/log2.h>
 
 #include <asm/unistd.h>
 
@@ -446,8 +447,43 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
 	if (ipcp->key != IPC_PRIVATE)
-		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
-				       ipc_kht_params);
+		WARN_ON_ONCE(rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
+				       ipc_kht_params));
+}
+
+/**
+ * ipc_search_maxidx - search for the highest assigned index
+ * @ids: ipc identifier set
+ * @limit: known upper limit for highest assigned index
+ *
+ * The function determines the highest assigned index in @ids. It is intended
+ * to be called when ids->max_idx needs to be updated.
+ * Updating ids->max_idx is necessary when the current highest index ipc
+ * object is deleted.
+ * If no ipc object is allocated, then -1 is returned.
+ *
+ * ipc_ids.rwsem needs to be held by the caller.
+ */
+static int ipc_search_maxidx(struct ipc_ids *ids, int limit)
+{
+	int tmpidx;
+	int i;
+	int retval;
+
+	i = ilog2(limit+1);
+
+	retval = 0;
+	for (; i >= 0; i--) {
+		tmpidx = retval | (1<<i);
+		/*
+		 * "0" is a possible index value, thus search using
+		 * e.g. 15,7,3,1,0 instead of 16,8,4,2,1.
+		 */
+		tmpidx = tmpidx-1;
+		if (idr_get_next(&ids->ipcs_idr, &tmpidx))
+			retval |= (1<<i);
+	}
+	return retval - 1;
 }
 
 /**
@@ -462,17 +498,15 @@ void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
 	int idx = ipcid_to_idx(ipcp->id);
 
-	idr_remove(&ids->ipcs_idr, idx);
+	WARN_ON_ONCE(idr_remove(&ids->ipcs_idr, idx) != ipcp);
 	ipc_kht_remove(ids, ipcp);
 	ids->in_use--;
 	ipcp->deleted = true;
 
 	if (unlikely(idx == ids->max_idx)) {
-		do {
-			idx--;
-			if (idx == -1)
-				break;
-		} while (!idr_find(&ids->ipcs_idr, idx));
+		idx = ids->max_idx-1;
+		if (idx >= 0)
+			idx = ipc_search_maxidx(ids, idx);
 		ids->max_idx = idx;
 	}
 }
@@ -748,36 +782,37 @@ struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
 	return iter->pid_ns;
 }
 
-/*
- * This routine locks the ipc structure found at least at position pos.
+/**
+ * sysvipc_find_ipc - Find and lock the ipc structure based on seq pos
+ * @ids: ipc identifier set
+ * @pos: expected position
+ *
+ * The function finds an ipc structure, based on the sequence file
+ * position @pos. If there is no ipc structure at position @pos, then
+ * the successor is selected.
+ * If a structure is found, then it is locked (both rcu_read_lock() and
+ * ipc_lock_object()) and  @pos is set to the position needed to locate
+ * the found ipc structure.
+ * If nothing is found (i.e. EOF), @pos is not modified.
+ *
+ * The function returns the found ipc structure, or NULL at EOF.
  */
-static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
-					      loff_t *new_pos)
+static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t *pos)
 {
+	int tmpidx;
 	struct kern_ipc_perm *ipc;
-	int total, id;
 
-	total = 0;
-	for (id = 0; id < pos && total < ids->in_use; id++) {
-		ipc = idr_find(&ids->ipcs_idr, id);
-		if (ipc != NULL)
-			total++;
-	}
+	/* convert from position to idr index -> "-1" */
+	tmpidx = *pos - 1;
 
-	ipc = NULL;
-	if (total >= ids->in_use)
-		goto out;
+	ipc = idr_get_next(&ids->ipcs_idr, &tmpidx);
+	if (ipc != NULL) {
+		rcu_read_lock();
+		ipc_lock_object(ipc);
 
-	for (; pos < ipc_mni; pos++) {
-		ipc = idr_find(&ids->ipcs_idr, pos);
-		if (ipc != NULL) {
-			rcu_read_lock();
-			ipc_lock_object(ipc);
-			break;
-		}
+		/* convert from idr index to position  -> "+1" */
+		*pos = tmpidx + 1;
 	}
-out:
-	*new_pos = pos + 1;
 	return ipc;
 }
 
@@ -791,11 +826,13 @@ static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 	if (ipc && ipc != SEQ_START_TOKEN)
 		ipc_unlock(ipc);
 
-	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
+	/* Next -> search for *pos+1 */
+	(*pos)++;
+	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], pos);
 }
 
 /*
- * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
+ * File positions: pos 0 -> header, pos n -> ipc idx = n - 1.
  * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
  */
 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
@@ -820,8 +857,8 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 	if (*pos == 0)
 		return SEQ_START_TOKEN;
 
-	/* Find the (pos-1)th ipc */
-	return sysvipc_find_ipc(ids, *pos - 1, pos);
+	/* Otherwise return the correct ipc structure */
+	return sysvipc_find_ipc(ids, pos);
 }
 
 static void sysvipc_proc_stop(struct seq_file *s, void *it)
@@ -868,7 +905,7 @@ static int sysvipc_proc_open(struct inode *inode, struct file *file)
 	if (!iter)
 		return -ENOMEM;
 
-	iter->iface = PDE_DATA(inode);
+	iter->iface = pde_data(inode);
 	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 	iter->pid_ns = get_pid_ns(task_active_pid_ns(current));