From: Karsten Graul <kgraul@linux.ibm.com>
Date: Fri, 8 Apr 2022 17:10:33 +0200
Subject: net/smc: use memcpy instead of snprintf to avoid out of bounds read
Git-commit: b1871fd48efc567650dbdc974e5a2342a03fe0d2
Patch-mainline: v5.18-rc3
References: git-fixes

Using snprintf() to convert not null-terminated strings to null
terminated strings may cause out of bounds read in the source string.
Therefore use memcpy() and terminate the target string with a null
afterwards.

Fixes: fa0866625543 ("net/smc: add support for user defined EIDs")
Fixes: 3c572145c24e ("net/smc: add generic netlink support for system EID")
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 net/smc/smc_clc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -191,7 +191,8 @@ static int smc_nl_ueid_dumpinfo(struct s
 			  flags, SMC_NETLINK_DUMP_UEID);
 	if (!hdr)
 		return -ENOMEM;
-	snprintf(ueid_str, sizeof(ueid_str), "%s", ueid);
+	memcpy(ueid_str, ueid, SMC_MAX_EID_LEN);
+	ueid_str[SMC_MAX_EID_LEN] = 0;
 	if (nla_put_string(skb, SMC_NLA_EID_TABLE_ENTRY, ueid_str)) {
 		genlmsg_cancel(skb, hdr);
 		return -EMSGSIZE;
@@ -252,7 +253,8 @@ int smc_nl_dump_seid(struct sk_buff *skb
 		goto end;
 
 	smc_ism_get_system_eid(&seid);
-	snprintf(seid_str, sizeof(seid_str), "%s", seid);
+	memcpy(seid_str, seid, SMC_MAX_EID_LEN);
+	seid_str[SMC_MAX_EID_LEN] = 0;
 	if (nla_put_string(skb, SMC_NLA_SEID_ENTRY, seid_str))
 		goto err;
 	read_lock(&smc_clc_eid_table.lock);