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  1. 20 10月, 2012 3 次提交
  3. 12 10月, 2012 1 次提交
    • K
      xen/pv-on-hvm kexec: add quirk for Xen 3.4 and shutdown watches. · cb6b6df1
      由 Konrad Rzeszutek Wilk 提交于 
      The commit 254d1a3f, titled
"xen/pv-on-hvm kexec: shutdown watches from old kernel" assumes that the
XenBus backend can deal with reading of values from:
 "control/platform-feature-xs_reset_watches":

    ... a patch for xenstored is required so that it
    accepts the XS_RESET_WATCHES request from a client (see changeset
    23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
    the registration of watches will fail and some features of a PVonHVM
    guest are not available. The guest is still able to boot, but repeated
    kexec boots will fail."

Sadly this is not true when using a Xen 3.4 hypervisor and booting a PVHVM
guest. We end up hanging at:

  err = xenbus_scanf(XBT_NIL, "control",
                        "platform-feature-xs_reset_watches", "%d", &supported);

This can easily be seen with guests hanging at xenbus_init:

NX (Execute Disable) protection: active
SMBIOS 2.4 present.
DMI: Xen HVM domU, BIOS 3.4.0 05/13/2011
Hypervisor detected: Xen HVM
Xen version 3.4.
Xen Platform PCI: I/O protocol version 1
... snip ..
calling  xenbus_init+0x0/0x27e @ 1

Reverting the commit or using the attached patch fixes the issue. This fix
checks whether the hypervisor is older than 4.0 and if so does not try to
perform the read.

Fixes-Oracle-Bug: 14708233
CC: stable@vger.kernel.org
Acked-by: NOlaf Hering <olaf@aepfle.de>
[v2: Added a comment in the source code]
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      cb6b6df1
  5. 17 9月, 2012 1 次提交
  7. 20 7月, 2012 1 次提交
    • O
      xen/pv-on-hvm kexec: shutdown watches from old kernel · 254d1a3f
      由 Olaf Hering 提交于 
      Add xs_reset_watches function to shutdown watches from old kernel after
kexec boot.  The old kernel does not unregister all watches in the
shutdown path.  They are still active, the double registration can not
be detected by the new kernel.  When the watches fire, unexpected events
will arrive and the xenwatch thread will crash (jumps to NULL).  An
orderly reboot of a hvm guest will destroy the entire guest with all its
resources (including the watches) before it is rebuilt from scratch, so
the missing unregister is not an issue in that case.

With this change the xenstored is instructed to wipe all active watches
for the guest.  However, a patch for xenstored is required so that it
accepts the XS_RESET_WATCHES request from a client (see changeset
23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
the registration of watches will fail and some features of a PVonHVM
guest are not available. The guest is still able to boot, but repeated
kexec boots will fail.
Signed-off-by: NOlaf Hering <olaf@aepfle.de>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      254d1a3f
  9. 05 1月, 2012 2 次提交
    • I
      xen/xenbus: don't reimplement kvasprintf via a fixed size buffer · a800651e
      由 Ian Campbell 提交于 
      Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Cc: Haogang Chen <haogangchen@gmail.com>
Acked-by: NJan Beulich <JBeulich@suse.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      a800651e
    • I
      xen/xenbus: Reject replies with payload > XENSTORE_PAYLOAD_MAX. · 9e7860ce
      由 Ian Campbell 提交于 
      Haogang Chen found out that:

 There is a potential integer overflow in process_msg() that could result
 in cross-domain attack.

 	body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH);

 When a malicious guest passes 0xffffffff in msg->hdr.len, the subsequent
 call to xb_read() would write to a zero-length buffer.

 The other end of this connection is always the xenstore backend daemon
 so there is no guest (malicious or otherwise) which can do this. The
 xenstore daemon is a trusted component in the system.

 However this seem like a reasonable robustness improvement so we should
 have it.

And Ian when read the API docs found that:
        The payload length (len field of the header) is limited to 4096
        (XENSTORE_PAYLOAD_MAX) in both directions.  If a client exceeds the
        limit, its xenstored connection will be immediately killed by
        xenstored, which is usually catastrophic from the client's point of
        view.  Clients (particularly domains, which cannot just reconnect)
        should avoid this.

so this patch checks against that instead.

This also avoids a potential integer overflow pointed out by Haogang Chen.
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Cc: Haogang Chen <haogangchen@gmail.com>
CC: stable@kernel.org
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      9e7860ce
  11. 19 12月, 2011 1 次提交
  13. 27 9月, 2011 1 次提交
  15. 23 9月, 2011 1 次提交
    • O
      xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches from old kernel · ddacf5ef
      由 Olaf Hering 提交于 
      Add new xs_reset_watches function to shutdown watches from old kernel after
kexec boot.  The old kernel does not unregister all watches in the
shutdown path.  They are still active, the double registration can not
be detected by the new kernel.  When the watches fire, unexpected events
will arrive and the xenwatch thread will crash (jumps to NULL).  An
orderly reboot of a hvm guest will destroy the entire guest with all its
resources (including the watches) before it is rebuilt from scratch, so
the missing unregister is not an issue in that case.

With this change the xenstored is instructed to wipe all active watches
for the guest.  However, a patch for xenstored is required so that it
accepts the XS_RESET_WATCHES request from a client (see changeset
23839:42a45baf037d in xen-unstable.hg). Without the patch for xenstored
the registration of watches will fail and some features of a PVonHVM
guest are not available. The guest is still able to boot, but repeated
kexec boots will fail.

[v5: use xs_single instead of passing a dummy string to xs_talkv]
[v4: ignore -EEXIST in xs_reset_watches]
[v3: use XS_RESET_WATCHES instead of XS_INTRODUCE]
[v2: move all code which deals with XS_INTRODUCE into xs_introduce()
    (based on feedback from Ian Campbell); remove casts from kvec assignment]
Signed-off-by: NOlaf Hering <olaf@aepfle.de>
[v1: Redid the git description a bit]
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      ddacf5ef
  17. 01 9月, 2011 1 次提交
    • O
      xen/pv-on-hvm kexec: prevent crash in xenwatch_thread() when stale watch events arrive · c4c303c7
      由 Olaf Hering 提交于 
      During repeated kexec boots xenwatch_thread() can crash because
xenbus_watch->callback is cleared by xenbus_watch_path() if a node/token
combo for a new watch happens to match an already registered watch from
an old kernel.  In this case xs_watch returns -EEXISTS, then
register_xenbus_watch() does not remove the to-be-registered watch from
the list of active watches but returns the -EEXISTS to the caller
anyway.

Because the watch is still active in xenstored it will cause an event
which will arrive in the new kernel. process_msg() will find the
encapsulated struct xenbus_watch in its list of registered watches and
puts the "empty" watch handle in the queue for xenwatch_thread().
xenwatch_thread() then calls ->callback which was cleared earlier by
xenbus_watch_path().

To prevent that crash in a guest running on an old xen toolstack remove
the special -EEXIST handling.

v2:
 - remove the EEXIST handing in register_xenbus_watch() instead of
   checking for ->callback in process_msg()
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NOlaf Hering <olaf@aepfle.de>
      c4c303c7
  19. 03 6月, 2010 1 次提交
  21. 04 11月, 2009 1 次提交
  23. 31 3月, 2009 1 次提交
  25. 09 1月, 2009 1 次提交
  27. 03 7月, 2008 1 次提交
  29. 27 7月, 2007 1 次提交
  31. 18 7月, 2007 1 次提交