* [PATCH net] s390/qeth: reject oversized SNMP requests
@ 2019-08-23 9:29 Julian Wiedmann
2019-08-23 9:31 ` Julian Wiedmann
2019-08-24 23:35 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Julian Wiedmann @ 2019-08-23 9:29 UTC (permalink / raw)
To: David Miller
Cc: netdev, linux-s390, Heiko Carstens, Stefan Raspl, Ursula Braun,
Julian Wiedmann
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;
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net] s390/qeth: reject oversized SNMP requests
2019-08-23 9:29 [PATCH net] s390/qeth: reject oversized SNMP requests Julian Wiedmann
@ 2019-08-23 9:31 ` Julian Wiedmann
2019-08-24 23:35 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Julian Wiedmann @ 2019-08-23 9:31 UTC (permalink / raw)
To: David Miller
Cc: netdev, linux-s390, Heiko Carstens, Stefan Raspl, Ursula Braun,
Dan Carpenter
+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;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net] s390/qeth: reject oversized SNMP requests
2019-08-23 9:29 [PATCH net] s390/qeth: reject oversized SNMP requests Julian Wiedmann
2019-08-23 9:31 ` Julian Wiedmann
@ 2019-08-24 23:35 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2019-08-24 23:35 UTC (permalink / raw)
To: jwi; +Cc: netdev, linux-s390, heiko.carstens, raspl, ubraun
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.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-08-24 23:35 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-23 9:29 [PATCH net] s390/qeth: reject oversized SNMP requests Julian Wiedmann
2019-08-23 9:31 ` Julian Wiedmann
2019-08-24 23:35 ` David Miller
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).