qeth: avoid buffer overflow in snmp ioctl

commit 6fb392b1a63ae36c31f62bc3fc8630b49d602b62 upstream.

Check user-defined length in snmp ioctl request and allow request
only if it fits into a qeth command buffer.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Reviewed-by: Heiko Carstens <heicars2@linux.vnet.ibm.com>
Reported-by: Nico Golde <nico@ngolde.de>
Reported-by: Fabian Yamaguchi <fabs@goesec.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index 6cd0fc1b203a..e06cb8f8d0c2 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -4448,7 +4448,7 @@ int qeth_snmp_command(struct qeth_card *card, char __user *udata)
         struct qeth_cmd_buffer *iob;
         struct qeth_ipa_cmd *cmd;
         struct qeth_snmp_ureq *ureq;
-        int req_len;
+        unsigned int req_len;
         struct qeth_arp_query_info qinfo = {0, };
         int rc = 0;
 
@@ -4464,6 +4464,10 @@ int qeth_snmp_command(struct qeth_card *card, char __user *udata)
         /* skip 4 bytes (data_len struct member) to get req_len */
         if (copy_from_user(&req_len, udata + sizeof(int), sizeof(int)))
                 return -EFAULT;
+        if (req_len > (QETH_BUFSIZE - IPA_PDU_HEADER_SIZE -
+                       sizeof(struct qeth_ipacmd_hdr) -
+                       sizeof(struct qeth_ipacmd_setadpparms_hdr)))
+                return -EINVAL;
         ureq = memdup_user(udata, req_len + sizeof(struct qeth_snmp_ureq_hdr));
         if (IS_ERR(ureq)) {
                 QETH_CARD_TEXT(card, 2, "snmpnome");