[Qemu-devel] [Bug 1703147] [NEW] Xfer:features:read truncating xml sent to gdb frontends

[Qemu-devel] [Bug 1703147] [NEW] Xfer:features:read truncating xml sent to gdb frontends

[Duane Voth]

Public bug reported:

Around line 1326 in gdbstub.c:

            if (len > (MAX_PACKET_LENGTH - 5) / 2)
                len = (MAX_PACKET_LENGTH - 5) / 2;

is truncating processor reg description xml files longer than 2045
bytes.  Deleting these lines works for my immediate need, but they seem
to be trying to fix some buffer overrun condition so I won't offer a
patch until we understand their purpose.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1703147

Title:
  Xfer:features:read truncating xml sent to gdb frontends

Status in QEMU:
  New

Bug description:
  Around line 1326 in gdbstub.c:

              if (len > (MAX_PACKET_LENGTH - 5) / 2)
                  len = (MAX_PACKET_LENGTH - 5) / 2;

  is truncating processor reg description xml files longer than 2045
  bytes.  Deleting these lines works for my immediate need, but they
  seem to be trying to fix some buffer overrun condition so I won't
  offer a patch until we understand their purpose.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1703147/+subscriptions

Re: [Qemu-devel] [Bug 1703147] [NEW] Xfer:features:read truncating xml sent to gdb frontends

[Peter Maydell]

On 8 July 2017 at 22:19, Duane Voth <duanev@gmail.com> wrote:
> Around line 1326 in gdbstub.c:
>
>             if (len > (MAX_PACKET_LENGTH - 5) / 2)
>                 len = (MAX_PACKET_LENGTH - 5) / 2;
>
> is truncating processor reg description xml files longer than 2045
> bytes.  Deleting these lines works for my immediate need, but they seem
> to be trying to fix some buffer overrun condition so I won't offer a
> patch until we understand their purpose.

Those lines prevent the packet we're constructing overrunning
the buf[] array (in the worst case the packet encoding could
use 2 bytes of buffer for every byte of payload). It's probably
working for you without them because (a) the XML payload doesn't
come near the worst-case and (b) buf[] is followed on the stack
by mem_buf[] which happens to be unused here so overrunning into
it has no visible harmful effects.

Truncating the XML is clearly not what we want though so we
should do something more intelligent...

thanks
-- PMM

[Bug 1703147] Re: Xfer:features:read truncating xml sent to gdb frontends

[Thomas Huth]

The QEMU project is currently considering to move its bug tracking to
another system. For this we need to know which bugs are still valid
and which could be closed already. Thus we are setting older bugs to
"Incomplete" now.

If you still think this bug report here is valid, then please switch
the state back to "New" within the next 60 days, otherwise this report
will be marked as "Expired". Or please mark it as "Fix Released" if
the problem has been solved with a newer version of QEMU already.

Thank you and sorry for the inconvenience.


** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1703147

Title:
  Xfer:features:read truncating xml sent to gdb frontends

Status in QEMU:
  Incomplete

Bug description:
  Around line 1326 in gdbstub.c:

              if (len > (MAX_PACKET_LENGTH - 5) / 2)
                  len = (MAX_PACKET_LENGTH - 5) / 2;

  is truncating processor reg description xml files longer than 2045
  bytes.  Deleting these lines works for my immediate need, but they
  seem to be trying to fix some buffer overrun condition so I won't
  offer a patch until we understand their purpose.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1703147/+subscriptions

[Bug 1703147] Re: Xfer:features:read truncating xml sent to gdb frontends

[Launchpad Bug Tracker]

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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Title:
  Xfer:features:read truncating xml sent to gdb frontends

Status in QEMU:
  Expired

Bug description:
  Around line 1326 in gdbstub.c:

              if (len > (MAX_PACKET_LENGTH - 5) / 2)
                  len = (MAX_PACKET_LENGTH - 5) / 2;

  is truncating processor reg description xml files longer than 2045
  bytes.  Deleting these lines works for my immediate need, but they
  seem to be trying to fix some buffer overrun condition so I won't
  offer a patch until we understand their purpose.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1703147/+subscriptions

[Bug 1703147] Re: Xfer:features:read truncating xml sent to gdb frontends

[Duane Voth]

Problematic code now around lines 2221 (in handle_query_xfer_features)
... lol I'm the only one impacted ... all the large register set cpus
can be affected.

** Changed in: qemu
       Status: Expired => New

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https://bugs.launchpad.net/bugs/1703147

Title:
  Xfer:features:read truncating xml sent to gdb frontends

Status in QEMU:
  New

Bug description:
  Around line 1326 in gdbstub.c:

              if (len > (MAX_PACKET_LENGTH - 5) / 2)
                  len = (MAX_PACKET_LENGTH - 5) / 2;

  is truncating processor reg description xml files longer than 2045
  bytes.  Deleting these lines works for my immediate need, but they
  seem to be trying to fix some buffer overrun condition so I won't
  offer a patch until we understand their purpose.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1703147/+subscriptions

[Bug 1703147] Re: Xfer:features:read truncating xml sent to gdb frontends

[Thomas Huth]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/458


** Changed in: qemu
       Status: New => Expired

** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #458
   https://gitlab.com/qemu-project/qemu/-/issues/458

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You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1703147

Title:
  Xfer:features:read truncating xml sent to gdb frontends

Status in QEMU:
  Expired

Bug description:
  Around line 1326 in gdbstub.c:

              if (len > (MAX_PACKET_LENGTH - 5) / 2)
                  len = (MAX_PACKET_LENGTH - 5) / 2;

  is truncating processor reg description xml files longer than 2045
  bytes.  Deleting these lines works for my immediate need, but they
  seem to be trying to fix some buffer overrun condition so I won't
  offer a patch until we understand their purpose.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1703147/+subscriptions