netdev - [PATCH net] smc: fix out of bound access in smc_nl_get_sys

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Message-Id: <20201230004841.1472141-1-kuba@kernel.org>
Date:   Tue, 29 Dec 2020 16:48:41 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     davem@...emloft.net
Cc:     kgraul@...ux.ibm.com, guvenc@...ux.ibm.com,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        syzbot+f4708c391121cfc58396@...kaller.appspotmail.com
Subject: [PATCH net] smc: fix out of bound access in smc_nl_get_sys_info()

smc_clc_get_hostname() sets the host pointer to a buffer
which is not NULL-terminated (see smc_clc_init()).

Reported-by: syzbot+f4708c391121cfc58396@...kaller.appspotmail.com
Fixes: 099b990bd11a ("net/smc: Add support for obtaining system information")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
 net/smc/smc_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 59342b519e34..8d866b4ed8f6 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -246,7 +246,8 @@ int smc_nl_get_sys_info(struct sk_buff *skb, struct netlink_callback *cb)
 		goto errattr;
 	smc_clc_get_hostname(&host);
 	if (host) {
-		snprintf(hostname, sizeof(hostname), "%s", host);
+		memcpy(hostname, host, SMC_MAX_HOSTNAME_LEN);
+		hostname[SMC_MAX_HOSTNAME_LEN] = 0;
 		if (nla_put_string(skb, SMC_NLA_SYS_LOCAL_HOST, hostname))
 			goto errattr;
 	}
-- 
2.26.2