[RFC PATCH-for-9.0?] hw/net/net_tx_pkt: Fix overrun in update_sctp_checksum()

[RFC PATCH-for-9.0?] hw/net/net_tx_pkt: Fix overrun in update_sctp_checksum()

[Philippe Mathieu-Daudé]

If a fragmented packet size is too short, do not try to
calculate its checksum.

Reproduced using:

  $ cat << EOF | qemu-system-i386 -display none -nodefaults \
                                  -machine q35,accel=qtest -m 32M \
                                  -device igb,netdev=net0 \
                                  -netdev user,id=net0 \
                                  -qtest stdio
  outl 0xcf8 0x80000810
  outl 0xcfc 0xe0000000
  outl 0xcf8 0x80000804
  outw 0xcfc 0x06
  write 0xe0000403 0x1 0x02
  writel 0xe0003808 0xffffffff
  write 0xe000381a 0x1 0x5b
  write 0xe000381b 0x1 0x00
  EOF
  Assertion failed: (offset == 0), function iov_from_buf_full, file util/iov.c, line 39.
  #1 0x5575e81e952a in iov_from_buf_full qemu/util/iov.c:39:5
  #2 0x5575e6500768 in net_tx_pkt_update_sctp_checksum qemu/hw/net/net_tx_pkt.c:144:9
  #3 0x5575e659f3e1 in igb_setup_tx_offloads qemu/hw/net/igb_core.c:478:11
  #4 0x5575e659f3e1 in igb_tx_pkt_send qemu/hw/net/igb_core.c:552:10
  #5 0x5575e659f3e1 in igb_process_tx_desc qemu/hw/net/igb_core.c:671:17
  #6 0x5575e659f3e1 in igb_start_xmit qemu/hw/net/igb_core.c:903:9
  #7 0x5575e659f3e1 in igb_set_tdt qemu/hw/net/igb_core.c:2812:5
  #8 0x5575e657d6a4 in igb_core_write qemu/hw/net/igb_core.c:4248:9

Reported-by: Zheyu Ma <zheyuma97@gmail.com>
Fixes: f199b13bc1 ("igb: Implement Tx SCTP CSO")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2273
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
No clue this makes sense, but avoids the crash...
---
 hw/net/net_tx_pkt.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
index 2134a18c4c..6a8640157f 100644
--- a/hw/net/net_tx_pkt.c
+++ b/hw/net/net_tx_pkt.c
@@ -141,6 +141,10 @@ bool net_tx_pkt_update_sctp_checksum(struct NetTxPkt *pkt)
     uint32_t csum = 0;
     struct iovec *pl_start_frag = pkt->vec + NET_TX_PKT_PL_START_FRAG;
 
+    if (iov_size(pl_start_frag, pkt->payload_frags) < sizeof(csum)) {
+        return false;
+    }
+
     if (iov_from_buf(pl_start_frag, pkt->payload_frags, 8, &csum, sizeof(csum)) < sizeof(csum)) {
         return false;
     }
-- 
2.41.0

Re: [RFC PATCH-for-9.0?] hw/net/net_tx_pkt: Fix overrun in update_sctp_checksum()

[Akihiko Odaki]

On 2024/04/10 3:04, Philippe Mathieu-Daudé wrote:
> If a fragmented packet size is too short, do not try to
> calculate its checksum.
> 
> Reproduced using:
> 
>    $ cat << EOF | qemu-system-i386 -display none -nodefaults \
>                                    -machine q35,accel=qtest -m 32M \
>                                    -device igb,netdev=net0 \
>                                    -netdev user,id=net0 \
>                                    -qtest stdio
>    outl 0xcf8 0x80000810
>    outl 0xcfc 0xe0000000
>    outl 0xcf8 0x80000804
>    outw 0xcfc 0x06
>    write 0xe0000403 0x1 0x02
>    writel 0xe0003808 0xffffffff
>    write 0xe000381a 0x1 0x5b
>    write 0xe000381b 0x1 0x00
>    EOF
>    Assertion failed: (offset == 0), function iov_from_buf_full, file util/iov.c, line 39.
>    #1 0x5575e81e952a in iov_from_buf_full qemu/util/iov.c:39:5
>    #2 0x5575e6500768 in net_tx_pkt_update_sctp_checksum qemu/hw/net/net_tx_pkt.c:144:9
>    #3 0x5575e659f3e1 in igb_setup_tx_offloads qemu/hw/net/igb_core.c:478:11
>    #4 0x5575e659f3e1 in igb_tx_pkt_send qemu/hw/net/igb_core.c:552:10
>    #5 0x5575e659f3e1 in igb_process_tx_desc qemu/hw/net/igb_core.c:671:17
>    #6 0x5575e659f3e1 in igb_start_xmit qemu/hw/net/igb_core.c:903:9
>    #7 0x5575e659f3e1 in igb_set_tdt qemu/hw/net/igb_core.c:2812:5
>    #8 0x5575e657d6a4 in igb_core_write qemu/hw/net/igb_core.c:4248:9
> 
> Reported-by: Zheyu Ma <zheyuma97@gmail.com>
> Fixes: f199b13bc1 ("igb: Implement Tx SCTP CSO")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2273
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> No clue this makes sense, but avoids the crash...
> ---
>   hw/net/net_tx_pkt.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
> index 2134a18c4c..6a8640157f 100644
> --- a/hw/net/net_tx_pkt.c
> +++ b/hw/net/net_tx_pkt.c
> @@ -141,6 +141,10 @@ bool net_tx_pkt_update_sctp_checksum(struct NetTxPkt *pkt)
>       uint32_t csum = 0;
>       struct iovec *pl_start_frag = pkt->vec + NET_TX_PKT_PL_START_FRAG;
>   
> +    if (iov_size(pl_start_frag, pkt->payload_frags) < sizeof(csum)) {
> +        return false;
> +    }
> +

iov_from_buf() uses 8 as offset, so we should check if the size >= 8 + 
sizeof(csum).

However I doubt that it is worth to fix. I think it is fine to remove 
the assertion (i.e., remove the requirement that the offset specified 
for iov_from_buf() must be inside iov and instead let the function() 
return 0 in that case).

Regards,
Akihiko Odaki

>       if (iov_from_buf(pl_start_frag, pkt->payload_frags, 8, &csum, sizeof(csum)) < sizeof(csum)) {
>           return false;
>       }

Re: [RFC PATCH-for-9.0?] hw/net/net_tx_pkt: Fix overrun in update_sctp_checksum()

[Philippe Mathieu-Daudé]

On 10/4/24 08:53, Akihiko Odaki wrote:
> On 2024/04/10 3:04, Philippe Mathieu-Daudé wrote:
>> If a fragmented packet size is too short, do not try to
>> calculate its checksum.
>>
>> Reproduced using:
>>
>>    $ cat << EOF | qemu-system-i386 -display none -nodefaults \
>>                                    -machine q35,accel=qtest -m 32M \
>>                                    -device igb,netdev=net0 \
>>                                    -netdev user,id=net0 \
>>                                    -qtest stdio
>>    outl 0xcf8 0x80000810
>>    outl 0xcfc 0xe0000000
>>    outl 0xcf8 0x80000804
>>    outw 0xcfc 0x06
>>    write 0xe0000403 0x1 0x02
>>    writel 0xe0003808 0xffffffff
>>    write 0xe000381a 0x1 0x5b
>>    write 0xe000381b 0x1 0x00
>>    EOF
>>    Assertion failed: (offset == 0), function iov_from_buf_full, file 
>> util/iov.c, line 39.
>>    #1 0x5575e81e952a in iov_from_buf_full qemu/util/iov.c:39:5
>>    #2 0x5575e6500768 in net_tx_pkt_update_sctp_checksum 
>> qemu/hw/net/net_tx_pkt.c:144:9
>>    #3 0x5575e659f3e1 in igb_setup_tx_offloads 
>> qemu/hw/net/igb_core.c:478:11
>>    #4 0x5575e659f3e1 in igb_tx_pkt_send qemu/hw/net/igb_core.c:552:10
>>    #5 0x5575e659f3e1 in igb_process_tx_desc qemu/hw/net/igb_core.c:671:17
>>    #6 0x5575e659f3e1 in igb_start_xmit qemu/hw/net/igb_core.c:903:9
>>    #7 0x5575e659f3e1 in igb_set_tdt qemu/hw/net/igb_core.c:2812:5
>>    #8 0x5575e657d6a4 in igb_core_write qemu/hw/net/igb_core.c:4248:9
>>
>> Reported-by: Zheyu Ma <zheyuma97@gmail.com>
>> Fixes: f199b13bc1 ("igb: Implement Tx SCTP CSO")
>> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2273
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>> No clue this makes sense, but avoids the crash...
>> ---
>>   hw/net/net_tx_pkt.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/hw/net/net_tx_pkt.c b/hw/net/net_tx_pkt.c
>> index 2134a18c4c..6a8640157f 100644
>> --- a/hw/net/net_tx_pkt.c
>> +++ b/hw/net/net_tx_pkt.c
>> @@ -141,6 +141,10 @@ bool net_tx_pkt_update_sctp_checksum(struct 
>> NetTxPkt *pkt)
>>       uint32_t csum = 0;
>>       struct iovec *pl_start_frag = pkt->vec + NET_TX_PKT_PL_START_FRAG;
>> +    if (iov_size(pl_start_frag, pkt->payload_frags) < sizeof(csum)) {
>> +        return false;
>> +    }
>> +
> 
> iov_from_buf() uses 8 as offset, so we should check if the size >= 8 + 
> sizeof(csum).

Indeed. I'll respin a v2.

> However I doubt that it is worth to fix. I think it is fine to remove 
> the assertion (i.e., remove the requirement that the offset specified 
> for iov_from_buf() must be inside iov and instead let the function() 
> return 0 in that case).

update_sctp_checksum() seems sensible enough to be fixed for 9.0.

Reworking iov_from_buf() is for 9.1. I'll let someone else do that.

Thanks for the quick review!

> Regards,
> Akihiko Odaki
> 
>>       if (iov_from_buf(pl_start_frag, pkt->payload_frags, 8, &csum, 
>> sizeof(csum)) < sizeof(csum)) {
>>           return false;
>>       }