netdev - Re: [PATCH net] s390/qeth: reject oversized SNMP requests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <c0339d7f-2809-fe5a-57bf-2f76cee83eb0@linux.ibm.com>
Date:   Fri, 23 Aug 2019 11:31:53 +0200
From:   Julian Wiedmann <jwi@...ux.ibm.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Stefan Raspl <raspl@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH net] s390/qeth: reject oversized SNMP requests

+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@...cle.com>
> Signed-off-by: Julian Wiedmann <jwi@...ux.ibm.com>
> Reviewed-by: Ursula Braun <ubraun@...ux.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;
>