[Xen-changelog] [xen stable-4.9] gnttab: fix "don't use possibly unbounded tail calls"

[patchbot@xxxxxxx]

commit 9bf14bbf990843bfec16a5d69d36cf46c7593d88
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Aug 21 15:57:24 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Aug 21 15:57:24 2017 +0200

    gnttab: fix "don't use possibly unbounded tail calls"
    
    The compat mode code also needs adjustment to deal with the changed
    return value from gnttab_copy().
    
    This is part of XSA-226.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: ca617570542e1d7d8de636d5396959bbf1dabab7
    master date: 2017-08-21 15:43:36 +0200
---
 xen/common/compat/grant_table.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/common/compat/grant_table.c b/xen/common/compat/grant_table.c
index f8c60a1..cce3ff0 100644
--- a/xen/common/compat/grant_table.c
+++ b/xen/common/compat/grant_table.c
@@ -258,9 +258,9 @@ int compat_grant_table_op(unsigned int cmd,
                 rc = gnttab_copy(guest_handle_cast(nat.uop, gnttab_copy_t), n);
             if ( rc > 0 )
             {
-                ASSERT(rc < n);
-                i -= n - rc;
-                n = rc;
+                ASSERT(rc <= n);
+                i -= rc;
+                n -= rc;
             }
             if ( rc >= 0 )
             {
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.9

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