[PATCH] hw/net: Fix read of uninitialized memory in ftgmac100

[PATCH] hw/net: Fix read of uninitialized memory in ftgmac100

[Stephen Longfield]

With the `size += 4` before the call to `crc32`, the CRC calculation
would overrun the buffer. Size is used in the while loop starting on
line 1009 to determine how much data to write back, with the last
four bytes coming from `crc_ptr`, so do need to increase it, but should
do this after the computation.

I'm unsure why this use of uninitialized memory in the CRC doesn't
result in CRC errors, but it seems clear to me that it should not be
included in the calculation.

Signed-off-by: Stephen Longfield <slongfield@google.com>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
---
 hw/net/ftgmac100.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/net/ftgmac100.c b/hw/net/ftgmac100.c
index 83ef0a783e..d3bf14be53 100644
--- a/hw/net/ftgmac100.c
+++ b/hw/net/ftgmac100.c
@@ -980,9 +980,9 @@ static ssize_t ftgmac100_receive(NetClientState *nc, const uint8_t *buf,
         return size;
     }

-    /* 4 bytes for the CRC.  */
-    size += 4;
     crc = cpu_to_be32(crc32(~0, buf, size));
+    /* Increase size by 4, loop below reads the last 4 bytes from crc_ptr. */
+    size += 4;
     crc_ptr = (uint8_t *) &crc;

     /* Huge frames are truncated.  */
--
2.39.0.314.g84b9a713c41-goog

Re: [PATCH] hw/net: Fix read of uninitialized memory in ftgmac100

[Cédric Le Goater]

On 12/20/22 23:14, Stephen Longfield wrote:
> With the `size += 4` before the call to `crc32`, the CRC calculation
> would overrun the buffer. Size is used in the while loop starting on
> line 1009 to determine how much data to write back, with the last
> four bytes coming from `crc_ptr`, so do need to increase it, but should
> do this after the computation.
> 
> I'm unsure why this use of uninitialized memory in the CRC doesn't
> result in CRC errors, but it seems clear to me that it should not be
> included in the calculation.
> 
> Signed-off-by: Stephen Longfield <slongfield@google.com>
> Reviewed-by: Hao Wu <wuhaotsh@google.com>


Reviewed-by: Cédric Le Goater <clg@kaod.org>

I think imx_fec.c is impacted also.

Thanks,

C.


> ---
>   hw/net/ftgmac100.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/net/ftgmac100.c b/hw/net/ftgmac100.c
> index 83ef0a783e..d3bf14be53 100644
> --- a/hw/net/ftgmac100.c
> +++ b/hw/net/ftgmac100.c
> @@ -980,9 +980,9 @@ static ssize_t ftgmac100_receive(NetClientState *nc, const uint8_t *buf,
>           return size;
>       }
> 
> -    /* 4 bytes for the CRC.  */
> -    size += 4;
>       crc = cpu_to_be32(crc32(~0, buf, size));
> +    /* Increase size by 4, loop below reads the last 4 bytes from crc_ptr. */
> +    size += 4;
>       crc_ptr = (uint8_t *) &crc;
> 
>       /* Huge frames are truncated.  */
> --
> 2.39.0.314.g84b9a713c41-goog
> 

Re: [PATCH] hw/net: Fix read of uninitialized memory in ftgmac100

[Stephen Longfield]

On Tue, Dec 20, 2022 at 11:30 PM Cédric Le Goater <clg@kaod.org> wrote:
>
> On 12/20/22 23:14, Stephen Longfield wrote:
> > With the `size += 4` before the call to `crc32`, the CRC calculation
> > would overrun the buffer. Size is used in the while loop starting on
> > line 1009 to determine how much data to write back, with the last
> > four bytes coming from `crc_ptr`, so do need to increase it, but should
> > do this after the computation.
> >
> > I'm unsure why this use of uninitialized memory in the CRC doesn't
> > result in CRC errors, but it seems clear to me that it should not be
> > included in the calculation.
> >
> > Signed-off-by: Stephen Longfield <slongfield@google.com>
> > Reviewed-by: Hao Wu <wuhaotsh@google.com>
>
>
> Reviewed-by: Cédric Le Goater <clg@kaod.org>
>
> I think imx_fec.c is impacted also.
>
> Thanks,
>
> C.
>

Thanks for pointing that out, looks to be exactly the same. I'll send
out a separate patch that fixes the issue in that file.

Best,

--Stephen

>
> > ---
> >   hw/net/ftgmac100.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/net/ftgmac100.c b/hw/net/ftgmac100.c
> > index 83ef0a783e..d3bf14be53 100644
> > --- a/hw/net/ftgmac100.c
> > +++ b/hw/net/ftgmac100.c
> > @@ -980,9 +980,9 @@ static ssize_t ftgmac100_receive(NetClientState *nc, const uint8_t *buf,
> >           return size;
> >       }
> >
> > -    /* 4 bytes for the CRC.  */
> > -    size += 4;
> >       crc = cpu_to_be32(crc32(~0, buf, size));
> > +    /* Increase size by 4, loop below reads the last 4 bytes from crc_ptr. */
> > +    size += 4;
> >       crc_ptr = (uint8_t *) &crc;
> >
> >       /* Huge frames are truncated.  */
> > --
> > 2.39.0.314.g84b9a713c41-goog
> >
>

Re: [PATCH] hw/net: Fix read of uninitialized memory in ftgmac100

[Stephen Longfield]

Does anything more need to happen with this patch before it can be
applied? Not sure if it had gotten lost over the holidays.

Best,

--Stephen


On Wed, Dec 21, 2022 at 9:58 AM Stephen Longfield <slongfield@google.com> wrote:
>
> On Tue, Dec 20, 2022 at 11:30 PM Cédric Le Goater <clg@kaod.org> wrote:
> >
> > On 12/20/22 23:14, Stephen Longfield wrote:
> > > With the `size += 4` before the call to `crc32`, the CRC calculation
> > > would overrun the buffer. Size is used in the while loop starting on
> > > line 1009 to determine how much data to write back, with the last
> > > four bytes coming from `crc_ptr`, so do need to increase it, but should
> > > do this after the computation.
> > >
> > > I'm unsure why this use of uninitialized memory in the CRC doesn't
> > > result in CRC errors, but it seems clear to me that it should not be
> > > included in the calculation.
> > >
> > > Signed-off-by: Stephen Longfield <slongfield@google.com>
> > > Reviewed-by: Hao Wu <wuhaotsh@google.com>
> >
> >
> > Reviewed-by: Cédric Le Goater <clg@kaod.org>
> >
> > I think imx_fec.c is impacted also.
> >
> > Thanks,
> >
> > C.
> >
>
> Thanks for pointing that out, looks to be exactly the same. I'll send
> out a separate patch that fixes the issue in that file.
>
> Best,
>
> --Stephen
>
> >
> > > ---
> > >   hw/net/ftgmac100.c | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/hw/net/ftgmac100.c b/hw/net/ftgmac100.c
> > > index 83ef0a783e..d3bf14be53 100644
> > > --- a/hw/net/ftgmac100.c
> > > +++ b/hw/net/ftgmac100.c
> > > @@ -980,9 +980,9 @@ static ssize_t ftgmac100_receive(NetClientState *nc, const uint8_t *buf,
> > >           return size;
> > >       }
> > >
> > > -    /* 4 bytes for the CRC.  */
> > > -    size += 4;
> > >       crc = cpu_to_be32(crc32(~0, buf, size));
> > > +    /* Increase size by 4, loop below reads the last 4 bytes from crc_ptr. */
> > > +    size += 4;
> > >       crc_ptr = (uint8_t *) &crc;
> > >
> > >       /* Huge frames are truncated.  */
> > > --
> > > 2.39.0.314.g84b9a713c41-goog
> > >
> >

Re: [PATCH] hw/net: Fix read of uninitialized memory in ftgmac100

[Cédric Le Goater]

On 1/9/23 18:50, Stephen Longfield wrote:
> Does anything more need to happen with this patch before it can be
> applied? Not sure if it had gotten lost over the holidays.

I queued it with other aspeed changes :

   https://github.com/legoater/qemu/commits/aspeed-8.0

We have some time before 8.0 is released.

Thanks,

C.


> 
> Best,
> 
> --Stephen
> 
> 
> On Wed, Dec 21, 2022 at 9:58 AM Stephen Longfield <slongfield@google.com> wrote:
>>
>> On Tue, Dec 20, 2022 at 11:30 PM Cédric Le Goater <clg@kaod.org> wrote:
>>>
>>> On 12/20/22 23:14, Stephen Longfield wrote:
>>>> With the `size += 4` before the call to `crc32`, the CRC calculation
>>>> would overrun the buffer. Size is used in the while loop starting on
>>>> line 1009 to determine how much data to write back, with the last
>>>> four bytes coming from `crc_ptr`, so do need to increase it, but should
>>>> do this after the computation.
>>>>
>>>> I'm unsure why this use of uninitialized memory in the CRC doesn't
>>>> result in CRC errors, but it seems clear to me that it should not be
>>>> included in the calculation.
>>>>
>>>> Signed-off-by: Stephen Longfield <slongfield@google.com>
>>>> Reviewed-by: Hao Wu <wuhaotsh@google.com>
>>>
>>>
>>> Reviewed-by: Cédric Le Goater <clg@kaod.org>
>>>
>>> I think imx_fec.c is impacted also.
>>>
>>> Thanks,
>>>
>>> C.
>>>
>>
>> Thanks for pointing that out, looks to be exactly the same. I'll send
>> out a separate patch that fixes the issue in that file.
>>
>> Best,
>>
>> --Stephen
>>
>>>
>>>> ---
>>>>    hw/net/ftgmac100.c | 4 ++--
>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/hw/net/ftgmac100.c b/hw/net/ftgmac100.c
>>>> index 83ef0a783e..d3bf14be53 100644
>>>> --- a/hw/net/ftgmac100.c
>>>> +++ b/hw/net/ftgmac100.c
>>>> @@ -980,9 +980,9 @@ static ssize_t ftgmac100_receive(NetClientState *nc, const uint8_t *buf,
>>>>            return size;
>>>>        }
>>>>
>>>> -    /* 4 bytes for the CRC.  */
>>>> -    size += 4;
>>>>        crc = cpu_to_be32(crc32(~0, buf, size));
>>>> +    /* Increase size by 4, loop below reads the last 4 bytes from crc_ptr. */
>>>> +    size += 4;
>>>>        crc_ptr = (uint8_t *) &crc;
>>>>
>>>>        /* Huge frames are truncated.  */
>>>> --
>>>> 2.39.0.314.g84b9a713c41-goog
>>>>
>>>