netdev - RE: [PATCH v2] hv_netvsc: Fix a warning triggered by memcpy in rndis

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Message-ID: <BYAPR21MB1688C0BE9914B06E2937B6BCD7229@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Wed, 12 Oct 2022 01:56:56 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Cezar Bulinaru <cbulinaru@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH v2] hv_netvsc: Fix a warning triggered by memcpy in
 rndis_filter

From: Cezar Bulinaru <cbulinaru@...il.com> Sent: Tuesday, October 11, 2022 6:39 PM
> 
> A warning is triggered when the response message len exceeds
> the size of rndis_message. Inside the rndis_request structure
> these fields are however followed by a RNDIS_EXT_LEN padding
> so it is safe to use unsafe_memcpy.
> 
> memcpy: detected field-spanning write (size 168) of single field "(void *)&request-
> >response_msg + (sizeof(struct rndis_message) - sizeof(union
> rndis_message_container)) + sizeof(*req_id)" at drivers/net/hyperv/rndis_filter.c:338
> (size 40)
> RSP: 0018:ffffc90000144de0 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffff8881766b4000 RCX: 0000000000000000
> RDX: 0000000000000102 RSI: 0000000000009ffb RDI: 00000000ffffffff
> RBP: ffffc90000144e38 R08: 0000000000000000 R09: 00000000ffffdfff
> R10: ffffc90000144c48 R11: ffffffff82f56ac8 R12: ffff8881766b403c
> R13: 00000000000000a8 R14: ffff888100b75000 R15: ffff888179301d00
> FS:  0000000000000000(0000) GS:ffff8884d6280000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055f8b024c418 CR3: 0000000176548001 CR4: 00000000003706e0
> Call Trace:
>  <IRQ>
>  ? _raw_spin_unlock_irqrestore+0x27/0x50
>  netvsc_poll+0x556/0x940 [hv_netvsc]
>  __napi_poll+0x2e/0x170
>  net_rx_action+0x299/0x2f0
>  __do_softirq+0xed/0x2ef
>  __irq_exit_rcu+0x9f/0x110
>  irq_exit_rcu+0xe/0x20
>  sysvec_hyperv_callback+0xb0/0xd0
>  </IRQ>
>  <TASK>
>  asm_sysvec_hyperv_callback+0x1b/0x20
> RIP: 0010:native_safe_halt+0xb/0x10
> 
> Signed-off-by: Cezar Bulinaru <cbulinaru@...il.com>
> ---
>  drivers/net/hyperv/rndis_filter.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
> index 11f767a20444..eea777ec2541 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -20,6 +20,7 @@
>  #include <linux/vmalloc.h>
>  #include <linux/rtnetlink.h>
>  #include <linux/ucs2_string.h>
> +#include <linux/string.h>
> 
>  #include "hyperv_net.h"
>  #include "netvsc_trace.h"
> @@ -335,9 +336,10 @@ static void rndis_filter_receive_response(struct net_device
> *ndev,
>                 if (resp->msg_len <=
>                     sizeof(struct rndis_message) + RNDIS_EXT_LEN) {
>                         memcpy(&request->response_msg, resp, RNDIS_HEADER_SIZE +
> sizeof(*req_id));
> -                       memcpy((void *)&request->response_msg + RNDIS_HEADER_SIZE +
> sizeof(*req_id),
> +                       unsafe_memcpy((void *)&request->response_msg +
> RNDIS_HEADER_SIZE + sizeof(*req_id),
>                                data + RNDIS_HEADER_SIZE + sizeof(*req_id),
> -                              resp->msg_len - RNDIS_HEADER_SIZE - sizeof(*req_id));
> +                              resp->msg_len - RNDIS_HEADER_SIZE - sizeof(*req_id),
> +                              "request->response_msg is followed by a padding of RNDIS_EXT_LEN
> inside rndis_request");
>                         if (request->request_msg.ndis_msg_type ==
>                             RNDIS_MSG_QUERY && request->request_msg.msg.
>                             query_req.oid == RNDIS_OID_GEN_MEDIA_CONNECT_STATUS)
> --
> 2.37.1

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>