1 files changed, 134 insertions, 0 deletions
diff --git a/main/xen/xsa226-1.patch b/main/xen/xsa226-1.patch
new file mode 100644
index 0000000000..7711d3f888
--- /dev/null
+++ b/main/xen/xsa226-1.patch
@@ -0,0 +1,134 @@
+From: Jan Beulich <jbeulich@suse.com>
+Subject: gnttab: don't use possibly unbounded tail calls
+
+There is no guarantee that the compiler would actually translate them
+to branches instead of calls, so only ones with a known recursion limit
+are okay:
+- __release_grant_for_copy() can call itself only once, as
+  __acquire_grant_for_copy() won't permit use of multi-level transitive
+  grants,
+- __acquire_grant_for_copy() is fine to call itself with the last
+  argument false, as that prevents further recursion,
+- __acquire_grant_for_copy() must not call itself to recover from an
+  observed change to the active entry's pin count
+
+This is part of CVE-2017-12135 / XSA-226.
+
+Signed-off-by: Jan Beulich <jbeulich@suse.com>
+
+--- a/xen/common/grant_table.c
++++ b/xen/common/grant_table.c
+@@ -2103,8 +2103,10 @@ __release_grant_for_copy(
+ 
+     if ( td != rd )
+     {
+-        /* Recursive calls, but they're tail calls, so it's
+-           okay. */
++        /*
++         * Recursive calls, but they're bounded (acquire permits only a single
++         * level of transitivity), so it's okay.
++         */
+         if ( released_write )
+             __release_grant_for_copy(td, trans_gref, 0);
+         else if ( released_read )
+@@ -2255,10 +2257,11 @@ __acquire_grant_for_copy(
+                 return rc;
+             }
+ 
+-            /* We dropped the lock, so we have to check that nobody
+-               else tried to pin (or, for that matter, unpin) the
+-               reference in *this* domain.  If they did, just give up
+-               and try again. */
++            /*
++             * We dropped the lock, so we have to check that nobody else tried
++             * to pin (or, for that matter, unpin) the reference in *this*
++             * domain.  If they did, just give up and tell the caller to retry.
++             */
+             if ( act->pin != old_pin )
+             {
+                 __fixup_status_for_copy_pin(act, status);
+@@ -2266,9 +2269,8 @@ __acquire_grant_for_copy(
+                 active_entry_release(act);
+                 grant_read_unlock(rgt);
+                 put_page(*page);
+-                return __acquire_grant_for_copy(rd, gref, ldom, readonly,
+-                                                frame, page, page_off, length,
+-                                                allow_transitive);
++                *page = NULL;
++                return ERESTART;
+             }
+ 
+             /* The actual remote remote grant may or may not be a
+@@ -2574,7 +2576,7 @@ static int gnttab_copy_one(const struct
+     {
+         gnttab_copy_release_buf(src);
+         rc = gnttab_copy_claim_buf(op, &op->source, src, GNTCOPY_source_gref);
+-        if ( rc < 0 )
++        if ( rc )
+             goto out;
+     }
+ 
+@@ -2584,7 +2586,7 @@ static int gnttab_copy_one(const struct
+     {
+         gnttab_copy_release_buf(dest);
+         rc = gnttab_copy_claim_buf(op, &op->dest, dest, GNTCOPY_dest_gref);
+-        if ( rc < 0 )
++        if ( rc )
+             goto out;
+     }
+ 
+@@ -2593,6 +2595,14 @@ static int gnttab_copy_one(const struct
+     return rc;
+ }
+ 
++/*
++ * gnttab_copy(), other than the various other helpers of
++ * do_grant_table_op(), returns (besides possible error indicators)
++ * "count - i" rather than "i" to ensure that even if no progress
++ * was made at all (perhaps due to gnttab_copy_one() returning a
++ * positive value) a non-zero value is being handed back (zero needs
++ * to be avoided, as that means "success, all done").
++ */
+ static long gnttab_copy(
+     XEN_GUEST_HANDLE_PARAM(gnttab_copy_t) uop, unsigned int count)
+ {
+@@ -2606,7 +2616,7 @@ static long gnttab_copy(
+     {
+         if ( i && hypercall_preempt_check() )
+         {
+-            rc = i;
++            rc = count - i;
+             break;
+         }
+ 
+@@ -2616,13 +2626,20 @@ static long gnttab_copy(
+             break;
+         }
+ 
+-        op.status = gnttab_copy_one(&op, &dest, &src);
+-        if ( op.status != GNTST_okay )
++        rc = gnttab_copy_one(&op, &dest, &src);
++        if ( rc > 0 )
++        {
++            rc = count - i;
++            break;
++        }
++        if ( rc != GNTST_okay )
+         {
+             gnttab_copy_release_buf(&src);
+             gnttab_copy_release_buf(&dest);
+         }
+ 
++        op.status = rc;
++        rc = 0;
+         if ( unlikely(__copy_field_to_guest(uop, &op, status)) )
+         {
+             rc = -EFAULT;
+@@ -3160,6 +3177,7 @@ do_grant_table_op(
+         rc = gnttab_copy(copy, count);
+         if ( rc > 0 )
+         {
++            rc = count - rc;
+             guest_handle_add_offset(copy, rc);
+             uop = guest_handle_cast(copy, void);
+         }