[Qemu-devel] [Bug 932539] Re: qemu exits with -11 when connecting to a port redirect before the service starts listening

[Serge Hallyn]

inline void
insque(void *a, void *b)
{
        register struct quehead *element = (struct quehead *) a;
        register struct quehead *head = (struct quehead *) b;
        element->qh_link = head->qh_link;

(line 27 is the last line)

(gdb) p *element
Cannot access memory at address 0x0
(gdb) p a
$3 = (void *) 0x0

This is called from here in slirp/if.c:

        /* If there are more packets for this session, re-queue them */
        if (ifm->ifs_next != /* ifm->ifs_prev != */ ifm) {
                insque(ifm->ifs_next, ifqt);
                ifs_remque(ifm);
        }

It sounds like ifm expects its last element to have ifm->ifs_next = ifm,
but it's actually == NULL.

I don't see any changes to this file likely to have introduced the
regression, looking further up the stack.


** Also affects: qemu
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/932539

Title:
  qemu exits with -11 when connecting to a port redirect before the
  service starts listening

Status in QEMU:
  New
Status in “qemu-kvm” package in Ubuntu:
  Confirmed

Bug description:
  This was detected initially as a crash in the auto upgrade tester.
  The code of the upgrade tester basically spawns a kvm instance in the 
background with a port redirect from localhost:54322 to tcp:22 in the VM, then 
wait for that port to allow for a ssh connection before continuing the upgrade 
testing.

  In the past (Oneiric), all worked well but since Precise, we now get
  qemu exitting with -11 at every single test :(

  A quick reproducer is:
   - start a VM that has openssh-server installed with: -net 
user,hostfwd=tcp::54322-:22
   - immediately start "ssh -p 54322 127.0.0.1" before the VM starts booting 
(BIOS/GRUB state)

  Then wait for sshd to start in the VM and qemu will exit with -11.

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