The branch main has been updated by royger:
URL:
https://cgit.FreeBSD.org/src/commit/?id=4ece79968e70b96d3283f202635d49a4bf04a7e7
commit 4ece79968e70b96d3283f202635d49a4bf04a7e7
Author: Roger Pau Monné <roy...@freebsd.org>
AuthorDate: 2024-02-05 10:47:25 +0000
Commit: Roger Pau Monné <roy...@freebsd.org>
CommitDate: 2024-02-22 10:08:03 +0000
x86/xen: fix out of bounds access to the event channel masks on resume
When resuming from migration or suspension all regular event channels ports
are
reset to the INVALID_EVTCHN value, and drivers should re-initialize them
according to the new value provided by the other end of the connection.
However, the driver would first attempt to unbind the event channel handler
before attempting to bind it using the newly provided port. This unbind
uses
the stale event channel port that has been set to INVALID_EVTCHN for some
operations (notably as a result of the handler removal the interrupt
subsystem
ends up calling disable intr and source PIC hooks).
This was fine when INVALID_EVTCHN was 0, as then the operation would just
result in pointless setting of the 0 bit in the different event channel
related
control arrays (evtchn_{pending,mask} for example). However with the
change to
define INVALID_EVTCHN as ~0 the write is no longer pointless, and we end up
triggering a page-fault, or corrupting random data that happens to be
mapped at
the array position + ~0 bits.
In hindsight the change of INVALID_EVTCHN from 0 to ~0 was way more risky
than
initially assessed, and I believe has end up resulting in more fragile code
for
no real benefit.
Fix the disable intr and source wrappers to check whether the event channel
is
valid before attempting to use it.
Also introduce some extra KASSERTs in several array accesses in order to
avoid
out of bounds accesses if INVALID_EVTCHN ever reaches those functions.
Fixes: 1797ff962769 ('xen/intr: cleanup event channel number use')
MFC after: 1 week
Sponsored by: Cloud Software Group
Reviewed by: markj
Differential revision: https://reviews.freebsd.org/D43928
---
sys/dev/xen/bus/xen_intr.c | 8 ++++++--
sys/xen/evtchn/evtchnvar.h | 7 +++++--
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/sys/dev/xen/bus/xen_intr.c b/sys/dev/xen/bus/xen_intr.c
index 3fc8fb0fe83a..609f31b5418a 100644
--- a/sys/dev/xen/bus/xen_intr.c
+++ b/sys/dev/xen/bus/xen_intr.c
@@ -166,6 +166,7 @@ evtchn_cpu_mask_port(u_int cpu, evtchn_port_t port)
struct xen_intr_pcpu_data *pcpu;
pcpu = DPCPU_ID_PTR(cpu, xen_intr_pcpu);
+ KASSERT(is_valid_evtchn(port), ("Invalid event channel port"));
xen_clear_bit(port, pcpu->evtchn_enabled);
}
@@ -188,6 +189,7 @@ evtchn_cpu_unmask_port(u_int cpu, evtchn_port_t port)
struct xen_intr_pcpu_data *pcpu;
pcpu = DPCPU_ID_PTR(cpu, xen_intr_pcpu);
+ KASSERT(is_valid_evtchn(port), ("Invalid event channel port"));
xen_set_bit(port, pcpu->evtchn_enabled);
}
@@ -619,7 +621,8 @@ void
xen_intr_disable_intr(struct xenisrc *isrc)
{
- evtchn_mask_port(isrc->xi_port);
+ if (__predict_true(is_valid_evtchn(isrc->xi_port)))
+ evtchn_mask_port(isrc->xi_port);
}
/**
@@ -706,7 +709,8 @@ xen_intr_disable_source(struct xenisrc *isrc)
* unmasked by the generic interrupt code. The event channel
* device will unmask them when needed.
*/
- isrc->xi_masked = !!evtchn_test_and_set_mask(isrc->xi_port);
+ if (__predict_true(is_valid_evtchn(isrc->xi_port)))
+ isrc->xi_masked = !!evtchn_test_and_set_mask(isrc->xi_port);
}
/*
diff --git a/sys/xen/evtchn/evtchnvar.h b/sys/xen/evtchn/evtchnvar.h
index 455f7bcbd620..3e6575748f6b 100644
--- a/sys/xen/evtchn/evtchnvar.h
+++ b/sys/xen/evtchn/evtchnvar.h
@@ -37,8 +37,11 @@
#include <contrib/xen/event_channel.h>
/* Macros for accessing event channel values */
-#define EVTCHN_PTR(type, port) \
- (HYPERVISOR_shared_info->evtchn_##type + ((port) / __LONG_BIT))
+#define EVTCHN_PTR(type, port) ({
\
+ KASSERT(port < nitems(HYPERVISOR_shared_info->evtchn_##type) * \
+ sizeof(xen_ulong_t) * 8, ("Invalid event channel port")); \
+ (HYPERVISOR_shared_info->evtchn_##type + ((port) / __LONG_BIT));\
+})
#define EVTCHN_BIT(port) ((port) & (__LONG_BIT - 1))
#define EVTCHN_MASK(port) (1UL << EVTCHN_BIT(port))
