[Qemu-devel] [PATCH] vt82c686: avoid out-of-bounds read

[Qemu-devel] [PATCH] vt82c686: avoid out-of-bounds read

[Paolo Bonzini]

superio_ioport_readb can read the 256th element of the array.
Coverity reports an out-of-bounds write in superio_ioport_writeb,
but it does not show the corresponding out-of-bounds read
because it cannot prove that it can happen.  Fix the root
cause of the problem (zhanghailang's patch instead fixes
the logic in superio_ioport_writeb).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/isa/vt82c686.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
index e0c235c..a43e26d 100644
--- a/hw/isa/vt82c686.c
+++ b/hw/isa/vt82c686.c
@@ -36,7 +36,7 @@
 
 typedef struct SuperIOConfig
 {
-    uint8_t config[0xff];
+    uint8_t config[0x100];
     uint8_t index;
     uint8_t data;
 } SuperIOConfig;
-- 
1.8.3.1

Re: [Qemu-devel] [PATCH] vt82c686: avoid out-of-bounds read

[zhanghailiang]

Hi paolo,

Will this change affects the migration?
I noticed that there is a member 'SuperIOConfig superio_conf' in VT82C686BState.

vt82c686 seems only to be used in mips64el target, Do we support migration for mips target?

Thanks,
zhanghailiang

On 2014/12/10 17:17, Paolo Bonzini wrote:
> superio_ioport_readb can read the 256th element of the array.
> Coverity reports an out-of-bounds write in superio_ioport_writeb,
> but it does not show the corresponding out-of-bounds read
> because it cannot prove that it can happen.  Fix the root
> cause of the problem (zhanghailang's patch instead fixes
> the logic in superio_ioport_writeb).
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   hw/isa/vt82c686.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
> index e0c235c..a43e26d 100644
> --- a/hw/isa/vt82c686.c
> +++ b/hw/isa/vt82c686.c
> @@ -36,7 +36,7 @@
>
>   typedef struct SuperIOConfig
>   {
> -    uint8_t config[0xff];
> +    uint8_t config[0x100];
>       uint8_t index;
>       uint8_t data;
>   } SuperIOConfig;
>

Re: [Qemu-devel] [PATCH] vt82c686: avoid out-of-bounds read

[Paolo Bonzini]

On 10/12/2014 10:31, zhanghailiang wrote:
> Hi paolo,
> 
> Will this change affects the migration?
> I noticed that there is a member 'SuperIOConfig superio_conf' in
> VT82C686BState.
> 
> vt82c686 seems only to be used in mips64el target, Do we support
> migration for mips target?

No, there is no VMState for superio_conf.

Paolo

Re: [Qemu-devel] [PATCH] vt82c686: avoid out-of-bounds read

[zhanghailiang]

On 2014/12/10 17:17, Paolo Bonzini wrote:
> superio_ioport_readb can read the 256th element of the array.
> Coverity reports an out-of-bounds write in superio_ioport_writeb,
> but it does not show the corresponding out-of-bounds read
> because it cannot prove that it can happen.  Fix the root
> cause of the problem (zhanghailang's patch instead fixes
> the logic in superio_ioport_writeb).
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   hw/isa/vt82c686.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/isa/vt82c686.c b/hw/isa/vt82c686.c
> index e0c235c..a43e26d 100644
> --- a/hw/isa/vt82c686.c
> +++ b/hw/isa/vt82c686.c
> @@ -36,7 +36,7 @@
>
>   typedef struct SuperIOConfig
>   {
> -    uint8_t config[0xff];
> +    uint8_t config[0x100];
>       uint8_t index;
>       uint8_t data;
>   } SuperIOConfig;
>
Reviewed-by: zhanghailiang <zhang.zhanghailiang@huawei.com>

Re: [Qemu-devel] [Qemu-trivial] [PATCH] vt82c686: avoid out-of-bounds read

[Michael Tokarev]

10.12.2014 12:17, Paolo Bonzini wrote:
> superio_ioport_readb can read the 256th element of the array.

Is there a legitimate reason for it to access byte index 256?
What is the actual size of superio config memory, 256 or 257?
I don't know, but somehow it looks like it should be 256.
If that's the case, the fix is wrong and superio_ioport_readb()
should be fixed instead...

Thanks,

/mjt

Re: [Qemu-devel] [Qemu-trivial] [PATCH] vt82c686: avoid out-of-bounds read

[Paolo Bonzini]

On 11/12/2014 18:55, Michael Tokarev wrote:
>> > superio_ioport_readb can read the 256th element of the array.
> Is there a legitimate reason for it to access byte index 256?

The 256th element is byte index 255. :)

> What is the actual size of superio config memory, 256 or 257?

It's 256 and the array is sized conf[0xff].

> I don't know, but somehow it looks like it should be 256.

That's what the patch does. :)

Paolo

Re: [Qemu-devel] [Qemu-trivial] [PATCH] vt82c686: avoid out-of-bounds read

[Michael Tokarev]

10.12.2014 12:17, Paolo Bonzini wrote:
> superio_ioport_readb can read the 256th element of the array.
> Coverity reports an out-of-bounds write in superio_ioport_writeb,
> but it does not show the corresponding out-of-bounds read
> because it cannot prove that it can happen.  Fix the root
> cause of the problem (zhanghailang's patch instead fixes
> the logic in superio_ioport_writeb).

(Finally) applied to -trivial, thanks!

/mjt