[PATCH net 1/3] net/smc: use memcpy instead of snprintf to avoid out of bounds read

Karsten Graul
2022-04-08T15:11:15Z

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>
---
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);
--
2.32.0