[Xen-changelog] [xen staging-4.8] ARM: disable grant table v2

[patchbot@xxxxxxx]

commit 04061641b612fe253bceb71845751acf25aa24f7
Author:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
AuthorDate: Tue Aug 14 11:20:53 2018 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Aug 14 17:27:26 2018 +0100

    ARM: disable grant table v2
    
    It was never expected to work, the implementation is incomplete.
    
    As a side effect, it also prevents guests from triggering a
    "BUG_ON(page_get_owner(pg) != d)" in gnttab_unpopulate_status_frames().
    
    This is XSA-268.
    
    Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    (cherry picked from commit 9a5c16a3e75778c8a094ca87784d93b74676f46c)
---
 docs/misc/xen-command-line.markdown | 2 ++
 xen/common/grant_table.c            | 6 +++++-
 xen/include/asm-arm/grant_table.h   | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 4e58c3c916..a8707669b1 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -871,6 +871,8 @@ version are 1 and 2.
 use of grant table v2 without transitive grants is an ABI breakage from the
 guests point of view.
 
+The usage of gnttab v2 is not security supported on ARM platforms.
+
 ### gnttab\_max\_frames
 > `= <integer>`
 
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 3ec826a7a6..a8987c0865 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -62,7 +62,11 @@ integer_param("gnttab_max_frames", max_grant_frames);
 static unsigned int __read_mostly max_maptrack_frames;
 integer_param("gnttab_max_maptrack_frames", max_maptrack_frames);
 
-static unsigned int __read_mostly opt_gnttab_max_version = 2;
+#ifndef GNTTAB_MAX_VERSION
+#define GNTTAB_MAX_VERSION 2
+#endif
+
+static unsigned int __read_mostly opt_gnttab_max_version = GNTTAB_MAX_VERSION;
 static bool __read_mostly opt_transitive_grants = true;
 
 static int __init parse_gnttab(const char *s)
diff --git a/xen/include/asm-arm/grant_table.h 
b/xen/include/asm-arm/grant_table.h
index 2f9224fb7a..b47220c1c6 100644
--- a/xen/include/asm-arm/grant_table.h
+++ b/xen/include/asm-arm/grant_table.h
@@ -4,6 +4,7 @@
 #include <xen/grant_table.h>
 
 #define INITIAL_NR_GRANT_FRAMES 4
+#define GNTTAB_MAX_VERSION 1
 
 void gnttab_clear_flag(unsigned long nr, uint16_t *addr);
 int create_grant_host_mapping(unsigned long gpaddr,
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.8

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