[Linux-kernel-mentees] [PATCH net] tipc: Fix memory leak in tipc_group_create_member()

[Peilin Ye <yepeilin.cs@gmail.com>]

tipc_group_add_to_tree() returns silently if `key` matches `nkey` of an
existing node, causing tipc_group_create_member() to leak memory. Let
tipc_group_add_to_tree() return an error in such a case, so that
tipc_group_create_member() can handle it properly.

Fixes: 75da2163dbb6 ("tipc: introduce communication groups")
Reported-and-tested-by: syzbot+f95d90c454864b3b5bc9@syzkaller.appspotmail.com
Cc: Hillf Danton <hdanton@sina.com>
Link: https://syzkaller.appspot.com/bug?id=048390604fe1b60df34150265479202f10e13aff
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
Decoded syzbot reproducer in pseudo-C:

	fd0 = socket(AF_TIPC, SOCK_DGRAM, 0);

	sockaddr_tipc.family = AF_TIPC;
	sockaddr_tipc.addrtype = TIPC_ADDR_NAMESEQ;
	sockaddr_tipc.scope = 0;
	sockaddr_tipc.addr.namesq.type = TIPC_RESERVED_TYPES + 1;
	bind(fd0, &sockaddr_tipc, sizeof(sockaddr_tipc));

	tipc_group_req0.type = TIPC_RESERVED_TYPES + 1;
	setsockopt(fd0, SOL_TIPC, TIPC_GROUP_JOIN, &tipc_group_req0, sizeof(tipc_group_req0));

	fd1 = socket(AF_TIPC, SOCK_STREAM, 0);

	tipc_group_req1.type = TIPC_RESERVED_TYPES + 1;
	tipc_group_req1.scope = TIPC_CLUSTER_SCOPE;
	setsockopt(fd1, SOL_TIPC, TIPC_GROUP_JOIN, &tipc_group_req1, sizeof(tipc_group_req1));

 net/tipc/group.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/net/tipc/group.c b/net/tipc/group.c
index 588c2d2b0c69..553cf08b4d76 100644
--- a/net/tipc/group.c
+++ b/net/tipc/group.c
@@ -273,8 +273,8 @@ static struct tipc_member *tipc_group_find_node(struct tipc_group *grp,
 	return NULL;
 }
 
-static void tipc_group_add_to_tree(struct tipc_group *grp,
-				   struct tipc_member *m)
+static int tipc_group_add_to_tree(struct tipc_group *grp,
+				  struct tipc_member *m)
 {
 	u64 nkey, key = (u64)m->node << 32 | m->port;
 	struct rb_node **n, *parent = NULL;
@@ -291,10 +291,11 @@ static void tipc_group_add_to_tree(struct tipc_group *grp,
 		else if (key > nkey)
 			n = &(*n)->rb_right;
 		else
-			return;
+			return -1;
 	}
 	rb_link_node(&m->tree_node, parent, n);
 	rb_insert_color(&m->tree_node, &grp->members);
+	return 0;
 }
 
 static struct tipc_member *tipc_group_create_member(struct tipc_group *grp,
@@ -302,6 +303,7 @@ static struct tipc_member *tipc_group_create_member(struct tipc_group *grp,
 						    u32 instance, int state)
 {
 	struct tipc_member *m;
+	int ret;
 
 	m = kzalloc(sizeof(*m), GFP_ATOMIC);
 	if (!m)
@@ -314,8 +316,12 @@ static struct tipc_member *tipc_group_create_member(struct tipc_group *grp,
 	m->port = port;
 	m->instance = instance;
 	m->bc_acked = grp->bc_snd_nxt - 1;
+	ret = tipc_group_add_to_tree(grp, m);
+	if (ret < 0) {
+		kfree(m);
+		return NULL;
+	}
 	grp->member_cnt++;
-	tipc_group_add_to_tree(grp, m);
 	tipc_nlist_add(&grp->dests, m->node);
 	m->state = state;
 	return m;
-- 
2.25.1

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