| Message ID | 20190823092923.8507-1-jwi@linux.ibm.com |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] s390/qeth: reject oversized SNMP requests | expand |
+cc Dan On 23.08.19 11:29, Julian Wiedmann wrote: > 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 <dan.carpenter@oracle.com> > Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> > Reviewed-by: Ursula Braun <ubraun@linux.ibm.com> > --- > drivers/s390/net/qeth_core_main.c | 4 ++++ > 1 file changed, 4 insertions(+) > > 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; >
From: Julian Wiedmann <jwi@linux.ibm.com> Date: Fri, 23 Aug 2019 11:29:23 +0200 > 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 <dan.carpenter@oracle.com> > Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> > Reviewed-by: Ursula Braun <ubraun@linux.ibm.com> Applied.
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;
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 <dan.carpenter@oracle.com> Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> Reviewed-by: Ursula Braun <ubraun@linux.ibm.com> --- drivers/s390/net/qeth_core_main.c | 4 ++++ 1 file changed, 4 insertions(+)