[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 1/4] dt-overlay: Fix NULL pointer dereference
Hi,
On 30/09/2024 15:04, Michal Orzel wrote:
Hi Julien,
On 30/09/2024 12:37, Julien Grall wrote:
On 23/09/2024 12:05, Michal Orzel wrote:
Hi Julien,
Hi Michal,
On 20/09/2024 10:29, Julien Grall wrote:
Hi Michal,
On 19/09/2024 12:42, Michal Orzel wrote:
Attempt to attach an overlay (xl dt-overlay attach) to a domain without
first adding this overlay to Xen (xl dt-overlay add) results in an
overlay track entry being NULL in handle_attach_overlay_nodes(). This
leads to NULL pointer dereference and the following data abort crash:
(XEN) Cannot find any matching tracker with input dtbo. Operation is supported
only for prior added dtbo.
(XEN) Data Abort Trap. Syndrome=0x5
(XEN) Walking Hypervisor VA 0x40 on CPU0 via TTBR 0x0000000046948000
(XEN) 0TH[0x000] = 0x46940f7f
(XEN) 1ST[0x000] = 0x0
(XEN) CPU0: Unexpected Trap: Data Abort
(XEN) ----[ Xen-4.20-unstable arm64 debug=y Not tainted ]----
...
(XEN) Xen call trace:
(XEN) [<00000a0000208b30>] dt_overlay_domctl+0x304/0x370 (PC)
(XEN) [<00000a0000208b30>] dt_overlay_domctl+0x304/0x370 (LR)
(XEN) [<00000a0000274b7c>] arch_do_domctl+0x48/0x328
Fixes: 4c733873b5c2 ("xen/arm: Add XEN_DOMCTL_dt_overlay and device attachment to
domains")
Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
---
xen/common/dt-overlay.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/xen/common/dt-overlay.c b/xen/common/dt-overlay.c
index d53b4706cd2f..8606b14d1e8e 100644
--- a/xen/common/dt-overlay.c
+++ b/xen/common/dt-overlay.c
@@ -908,8 +908,11 @@ static long handle_attach_overlay_nodes(struct domain *d,
out:
spin_unlock(&overlay_lock);
- rangeset_destroy(entry->irq_ranges);
- rangeset_destroy(entry->iomem_ranges);
+ if ( entry )
+ {
+ rangeset_destroy(entry->irq_ranges);
+ rangeset_destroy(entry->iomem_ranges);
+ }
While looking at the error paths in handle_attach_overlay_nodes(), I
noticed we don't revert any partial changes made by handle_device().
In this case, I am wondering whether it is correct to destroy the
rangeset. How would you be able to revert the changes?
I guess the same story applies as for the partial add/remove which was stated
by Vikram
in the commit msg of 7e5c4a8b86f12942de0566b1d61f71d15774364b meaning partial
success withe some
failures may lead to other failures and might need a system reboot. I did not
carefully look into
this series, my plan was to fix the issues without changing the functional
behavior.
Do you mean in this series or forever? If the former, would you be able
to outline what you expect after the end of this series? What should
work? What should not work?
The goal of this series is to fix the issues I encountered while doing some
other DT overlay work
as stated in the patch 0. The goal of each patch is clearly outlined in the
commit message
by stating what is being fixed and why. The first 3 patches contain "Fixes" tag, therefore there> is no functional behavior change - only fixing what should have been
fixed by the original series.
Patch 4 does not have "Fixes" tag although in theory it could. There is no doc
mentioning that adding
nodes right into "/" is forbidden. Linux supports it so I added support for Xen
as well.
After end of *this* series I expect the issues mentioned in each patch to be
fixed + the ability to add
nodes directly under root node.
It's definitely not the end of fixes for this series.
Good. This wasn't clear from your wording. Thanks for clarification!
FWICS, we do not
yet support detachment (only add/remove and attach) and removal of nodes and
ranges is only
possible if the nodes are assigned to hwdom.
I need some clarifications. By "we do not yet support detachment", do
you mean while a guest is running or do you also include a domain
shutting down?In order to reason about detachment we need to go back to see
what is supported in terms of attachment.
At the moment, we can only attach dtbo to 1:1 domUs, therefore we can stop
talking about libxl domUs for now.
Ah, I missed the check. I thought we already supported device attachment
to guest started by xl.
For dom0less domUs, we also cannot really shut down them. So it leaves us with
dom0 whose reboot implies system
reboot. At the moment there is no code that would release IRQs and unmap MMIOs.
Understood. Then no action expected from my side for now. But it would
be good to keep track of the unknown issues when we will implement detach.
Cheers,
--
Julien Grall
|
