1 files changed, 87 insertions, 0 deletions
diff --git a/system/xen/xsa/xsa212.patch b/system/xen/xsa/xsa212.patch
new file mode 100644
index 0000000000..2c435c4136
--- /dev/null
+++ b/system/xen/xsa/xsa212.patch
@@ -0,0 +1,87 @@
+memory: properly check guest memory ranges in XENMEM_exchange handling
+
+The use of guest_handle_okay() here (as introduced by the XSA-29 fix)
+is insufficient here, guest_handle_subrange_okay() needs to be used
+instead.
+
+Note that the uses are okay in
+- XENMEM_add_to_physmap_batch handling due to the size field being only
+  16 bits wide,
+- livepatch_list() due to the limit of 1024 enforced on the
+  number-of-entries input (leaving aside the fact that this can be
+  called by a privileged domain only anyway),
+- compat mode handling due to counts there being limited to 32 bits,
+- everywhere else due to guest arrays being accessed sequentially from
+  index zero.
+
+This is XSA-212.
+
+Reported-by: Jann Horn <jannh@google.com>
+Signed-off-by: Jan Beulich <jbeulich@suse.com>
+Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
+
+--- a/xen/common/memory.c
++++ b/xen/common/memory.c
+@@ -436,8 +436,8 @@ static long memory_exchange(XEN_GUEST_HA
+         goto fail_early;
+     }
+ 
+-    if ( !guest_handle_okay(exch.in.extent_start, exch.in.nr_extents) ||
+-         !guest_handle_okay(exch.out.extent_start, exch.out.nr_extents) )
++    if ( !guest_handle_subrange_okay(exch.in.extent_start, exch.nr_exchanged,
++                                     exch.in.nr_extents - 1) )
+     {
+         rc = -EFAULT;
+         goto fail_early;
+@@ -447,11 +447,27 @@ static long memory_exchange(XEN_GUEST_HA
+     {
+         in_chunk_order  = exch.out.extent_order - exch.in.extent_order;
+         out_chunk_order = 0;
++
++        if ( !guest_handle_subrange_okay(exch.out.extent_start,
++                                         exch.nr_exchanged >> in_chunk_order,
++                                         exch.out.nr_extents - 1) )
++        {
++            rc = -EFAULT;
++            goto fail_early;
++        }
+     }
+     else
+     {
+         in_chunk_order  = 0;
+         out_chunk_order = exch.in.extent_order - exch.out.extent_order;
++
++        if ( !guest_handle_subrange_okay(exch.out.extent_start,
++                                         exch.nr_exchanged << out_chunk_order,
++                                         exch.out.nr_extents - 1) )
++        {
++            rc = -EFAULT;
++            goto fail_early;
++        }
+     }
+ 
+     d = rcu_lock_domain_by_any_id(exch.in.domid);
+--- a/xen/include/asm-x86/x86_64/uaccess.h
++++ b/xen/include/asm-x86/x86_64/uaccess.h
+@@ -29,8 +29,9 @@ extern void *xlat_malloc(unsigned long *
+ /*
+  * Valid if in +ve half of 48-bit address space, or above Xen-reserved area.
+  * This is also valid for range checks (addr, addr+size). As long as the
+- * start address is outside the Xen-reserved area then we will access a
+- * non-canonical address (and thus fault) before ever reaching VIRT_START.
++ * start address is outside the Xen-reserved area, sequential accesses
++ * (starting at addr) will hit a non-canonical address (and thus fault)
++ * before ever reaching VIRT_START.
+  */
+ #define __addr_ok(addr) \
+     (((unsigned long)(addr) < (1UL<<47)) || \
+@@ -40,7 +41,8 @@ extern void *xlat_malloc(unsigned long *
+     (__addr_ok(addr) || is_compat_arg_xlat_range(addr, size))
+ 
+ #define array_access_ok(addr, count, size) \
+-    (access_ok(addr, (count)*(size)))
++    (likely(((count) ?: 0UL) < (~0UL / (size))) && \
++     access_ok(addr, (count) * (size)))
+ 
+ #define __compat_addr_ok(d, addr) \
+     ((unsigned long)(addr) < HYPERVISOR_COMPAT_VIRT_START(d))