linux-kernel - [PATCH 5.17 094/219] net/smc: use memcpy instead of snprintf to avoid out of bounds read

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Date:   Mon, 18 Apr 2022 14:11:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Karsten Graul <kgraul@...ux.ibm.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 094/219] net/smc: use memcpy instead of snprintf to avoid out of bounds read

From: Karsten Graul <kgraul@...ux.ibm.com>

[ Upstream commit b1871fd48efc567650dbdc974e5a2342a03fe0d2 ]

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@...ux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/smc/smc_clc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
index ce27399b38b1..f9f3f59c79de 100644
--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -191,7 +191,8 @@ static int smc_nl_ueid_dumpinfo(struct sk_buff *skb, u32 portid, u32 seq,
 			  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, struct netlink_callback *cb)
 		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);
-- 
2.35.1