From 292a50e3fc2cf699587ea282e6253e0d6ae3cdc1 Mon Sep 17 00:00:00 2001 From: Julian Wiedmann Date: Fri, 23 Aug 2019 11:29:23 +0200 Subject: s390/qeth: reject oversized SNMP requests Commit d4c08afafa04 ("s390/qeth: streamline SNMP cmd code") removed the bounds checking for req_len, under the assumption that the check in qeth_alloc_cmd() would suffice. But that code path isn't sufficiently robust to handle a user-provided data_length, which could overflow (when adding the cmd header overhead) before being checked against QETH_BUFSIZE. We end up allocating just a tiny iob, and the subsequent copy_from_user() writes past the end of that iob. Special-case this path and add a coarse bounds check, to protect against maliciuous requests. This let's the subsequent code flow do its normal job and precise checking, without risk of overflow. Fixes: d4c08afafa04 ("s390/qeth: streamline SNMP cmd code") Reported-by: Dan Carpenter Signed-off-by: Julian Wiedmann Reviewed-by: Ursula Braun Signed-off-by: David S. Miller --- drivers/s390/net/qeth_core_main.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/s390/net/qeth_core_main.c') diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c index 9c3310c4d61d..6502b148541e 100644 --- a/drivers/s390/net/qeth_core_main.c +++ b/drivers/s390/net/qeth_core_main.c @@ -4374,6 +4374,10 @@ static int qeth_snmp_command(struct qeth_card *card, char __user *udata) get_user(req_len, &ureq->hdr.req_len)) return -EFAULT; + /* Sanitize user input, to avoid overflows in iob size calculation: */ + if (req_len > QETH_BUFSIZE) + return -EINVAL; + iob = qeth_get_adapter_cmd(card, IPA_SETADP_SET_SNMP_CONTROL, req_len); if (!iob) return -ENOMEM; -- cgit v1.2.3-59-g8ed1b