diff options
Diffstat (limited to 'system/xen/xsa/xsa342-4.13.patch')
| -rw-r--r-- | system/xen/xsa/xsa342-4.13.patch | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/system/xen/xsa/xsa342-4.13.patch b/system/xen/xsa/xsa342-4.13.patch new file mode 100644 index 0000000000000..334baf1b69c0d --- /dev/null +++ b/system/xen/xsa/xsa342-4.13.patch @@ -0,0 +1,145 @@ +From: Jan Beulich <jbeulich@suse.com> +Subject: evtchn/x86: enforce correct upper limit for 32-bit guests + +The recording of d->max_evtchns in evtchn_2l_init(), in particular with +the limited set of callers of the function, is insufficient. Neither for +PV nor for HVM guests the bitness is known at domain_create() time, yet +the upper bound in 2-level mode depends upon guest bitness. Recording +too high a limit "allows" x86 32-bit domains to open not properly usable +event channels, management of which (inside Xen) would then result in +corruption of the shared info and vCPU info structures. + +Keep the upper limit dynamic for the 2-level case, introducing a helper +function to retrieve the effective limit. This helper is now supposed to +be private to the event channel code. The used in do_poll() and +domain_dump_evtchn_info() weren't consistent with port uses elsewhere +and hence get switched to port_is_valid(). + +Furthermore FIFO mode's setup_ports() gets adjusted to loop only up to +the prior ABI limit, rather than all the way up to the new one. + +Finally a word on the change to do_poll(): Accessing ->max_evtchns +without holding a suitable lock was never safe, as it as well as +->evtchn_port_ops may change behind do_poll()'s back. Using +port_is_valid() instead widens some the window for potential abuse, +until we've dealt with the race altogether (see XSA-343). + +This is XSA-342. + +Reported-by: Julien Grall <jgrall@amazon.com> +Fixes: 48974e6ce52e ("evtchn: use a per-domain variable for the max number of event channels") +Signed-off-by: Jan Beulich <jbeulich@suse.com> +Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> +Reviewed-by: Julien Grall <jgrall@amazon.com> + +--- a/xen/common/event_2l.c ++++ b/xen/common/event_2l.c +@@ -103,7 +103,6 @@ static const struct evtchn_port_ops evtc + void evtchn_2l_init(struct domain *d) + { + d->evtchn_port_ops = &evtchn_port_ops_2l; +- d->max_evtchns = BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d); + } + + /* +--- a/xen/common/event_channel.c ++++ b/xen/common/event_channel.c +@@ -151,7 +151,7 @@ static void free_evtchn_bucket(struct do + + int evtchn_allocate_port(struct domain *d, evtchn_port_t port) + { +- if ( port > d->max_evtchn_port || port >= d->max_evtchns ) ++ if ( port > d->max_evtchn_port || port >= max_evtchns(d) ) + return -ENOSPC; + + if ( port_is_valid(d, port) ) +@@ -1396,13 +1396,11 @@ static void domain_dump_evtchn_info(stru + + spin_lock(&d->event_lock); + +- for ( port = 1; port < d->max_evtchns; ++port ) ++ for ( port = 1; port_is_valid(d, port); ++port ) + { + const struct evtchn *chn; + char *ssid; + +- if ( !port_is_valid(d, port) ) +- continue; + chn = evtchn_from_port(d, port); + if ( chn->state == ECS_FREE ) + continue; +--- a/xen/common/event_fifo.c ++++ b/xen/common/event_fifo.c +@@ -478,7 +478,7 @@ static void cleanup_event_array(struct d + d->evtchn_fifo = NULL; + } + +-static void setup_ports(struct domain *d) ++static void setup_ports(struct domain *d, unsigned int prev_evtchns) + { + unsigned int port; + +@@ -488,7 +488,7 @@ static void setup_ports(struct domain *d + * - save its pending state. + * - set default priority. + */ +- for ( port = 1; port < d->max_evtchns; port++ ) ++ for ( port = 1; port < prev_evtchns; port++ ) + { + struct evtchn *evtchn; + +@@ -546,6 +546,8 @@ int evtchn_fifo_init_control(struct evtc + if ( !d->evtchn_fifo ) + { + struct vcpu *vcb; ++ /* Latch the value before it changes during setup_event_array(). */ ++ unsigned int prev_evtchns = max_evtchns(d); + + for_each_vcpu ( d, vcb ) { + rc = setup_control_block(vcb); +@@ -562,8 +564,7 @@ int evtchn_fifo_init_control(struct evtc + goto error; + + d->evtchn_port_ops = &evtchn_port_ops_fifo; +- d->max_evtchns = EVTCHN_FIFO_NR_CHANNELS; +- setup_ports(d); ++ setup_ports(d, prev_evtchns); + } + else + rc = map_control_block(v, gfn, offset); +--- a/xen/common/schedule.c ++++ b/xen/common/schedule.c +@@ -1434,7 +1434,7 @@ static long do_poll(struct sched_poll *s + goto out; + + rc = -EINVAL; +- if ( port >= d->max_evtchns ) ++ if ( !port_is_valid(d, port) ) + goto out; + + rc = 0; +--- a/xen/include/xen/event.h ++++ b/xen/include/xen/event.h +@@ -105,6 +105,12 @@ void notify_via_xen_event_channel(struct + #define bucket_from_port(d, p) \ + ((group_from_port(d, p))[((p) % EVTCHNS_PER_GROUP) / EVTCHNS_PER_BUCKET]) + ++static inline unsigned int max_evtchns(const struct domain *d) ++{ ++ return d->evtchn_fifo ? EVTCHN_FIFO_NR_CHANNELS ++ : BITS_PER_EVTCHN_WORD(d) * BITS_PER_EVTCHN_WORD(d); ++} ++ + static inline bool_t port_is_valid(struct domain *d, unsigned int p) + { + if ( p >= read_atomic(&d->valid_evtchns) ) +--- a/xen/include/xen/sched.h ++++ b/xen/include/xen/sched.h +@@ -382,7 +382,6 @@ struct domain + /* Event channel information. */ + struct evtchn *evtchn; /* first bucket only */ + struct evtchn **evtchn_group[NR_EVTCHN_GROUPS]; /* all other buckets */ +- unsigned int max_evtchns; /* number supported by ABI */ + unsigned int max_evtchn_port; /* max permitted port number */ + unsigned int valid_evtchns; /* number of allocated event channels */ + spinlock_t event_lock; |