[tipc-discussion] [PATCH] tipc: fix uninit-value in tipc_nl_node_reset_link_stats

[Hoang Le]

syzbot found the following issue on:
==================================================================
BUG: KMSAN: uninit-value in strlen lib/string.c:495 [inline]
BUG: KMSAN: uninit-value in strstr+0xb4/0x2e0 lib/string.c:840
 strlen lib/string.c:495 [inline]
 strstr+0xb4/0x2e0 lib/string.c:840
 tipc_nl_node_reset_link_stats+0x41e/0xba0 net/tipc/node.c:2582
 genl_family_rcv_msg_doit net/netlink/genetlink.c:731 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
 genl_rcv_msg+0x103f/0x1260 net/netlink/genetlink.c:792
 netlink_rcv_skb+0x3a5/0x6c0 net/netlink/af_netlink.c:2501
 genl_rcv+0x3c/0x50 net/netlink/genetlink.c:803
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0xf3b/0x1270 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x1288/0x1440 net/netlink/af_netlink.c:1921
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg net/socket.c:734 [inline]
 ____sys_sendmsg+0xabc/0xe90 net/socket.c:2492
 ___sys_sendmsg+0x2a5/0x350 net/socket.c:2546
 __sys_sendmsg net/socket.c:2575 [inline]
 __do_sys_sendmsg net/socket.c:2584 [inline]
 __se_sys_sendmsg net/socket.c:2582 [inline]
 __x64_sys_sendmsg+0x367/0x540 net/socket.c:2582
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
==================================================================

This is because link name string is not validated before it's used
in calling strstr() and strlen().

Reported-by: syzbot+a73d24a22eeeebe5f...@syzkaller.appspotmail.com
Signed-off-by: Hoang Le <hoang.h...@dektech.com.au>
---
 net/tipc/node.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/tipc/node.c b/net/tipc/node.c
index b48d97cbbe29..23419a599471 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -2561,6 +2561,7 @@ int tipc_nl_node_reset_link_stats(struct sk_buff *skb, 
struct genl_info *info)
        struct net *net = sock_net(skb->sk);
        struct tipc_net *tn = tipc_net(net);
        struct tipc_link_entry *le;
+       int len;
 
        if (!info->attrs[TIPC_NLA_LINK])
                return -EINVAL;
@@ -2574,7 +2575,14 @@ int tipc_nl_node_reset_link_stats(struct sk_buff *skb, 
struct genl_info *info)
        if (!attrs[TIPC_NLA_LINK_NAME])
                return -EINVAL;
 
+       len = nla_len(attrs[TIPC_NLA_LINK_NAME]);
+       if (len <= 0)
+               return -EINVAL;
+
        link_name = nla_data(attrs[TIPC_NLA_LINK_NAME]);
+       len = min_t(int, len, TIPC_MAX_LINK_NAME);
+       if (!memchr(link_name, '\0', len))
+               return -EINVAL;
 
        err = -EINVAL;
        if (!strcmp(link_name, tipc_bclink_name)) {
-- 
2.30.2



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