[Xen-changelog] [xen master] libxc/x86: fix mapping of the start_info area

[patchbot@xxxxxxx]

commit d00385d80f151ee17eba35064a85769338ad6a74
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Wed Mar 28 12:55:15 2018 +0100
Commit:     Wei Liu <wei.liu2@xxxxxxxxxx>
CommitDate: Wed Mar 28 13:54:46 2018 +0100

    libxc/x86: fix mapping of the start_info area
    
    The start_info size calculated in bootlate_hvm is wrong. It should use
    HVMLOADER_MODULE_MAX_COUNT instead of dom->num_modules and it doesn't
    take into account the size of the modules command line.
    
    This is not a problem so far because the actually used amount of
    memory doesn't cross a page boundary, and so no page-fault is
    triggered.
    
    Instead of fixing the size calculation done in bootlate_hvm just map
    the amount of memory allocated in alloc_magic_pages_hvm.
    
    Suggested-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxc/xc_dom_x86.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c
index 0b65dab4bc..f4bacb9e28 100644
--- a/tools/libxc/xc_dom_x86.c
+++ b/tools/libxc/xc_dom_x86.c
@@ -1666,21 +1666,11 @@ static int bootlate_hvm(struct xc_dom_image *dom)
     uint32_t domid = dom->guest_domid;
     xc_interface *xch = dom->xch;
     struct hvm_start_info *start_info;
-    size_t start_info_size;
     struct hvm_modlist_entry *modlist;
     unsigned int i;
 
-    start_info_size = sizeof(*start_info) + dom->cmdline_size;
-    start_info_size += sizeof(struct hvm_modlist_entry) * dom->num_modules;
-
-    if ( start_info_size >
-         dom->start_info_seg.pages << XC_DOM_PAGE_SHIFT(dom) )
-    {
-        DOMPRINTF("Trying to map beyond start_info_seg");
-        return -1;
-    }
-
-    start_info = xc_map_foreign_range(xch, domid, start_info_size,
+    start_info = xc_map_foreign_range(xch, domid, dom->start_info_seg.pages <<
+                                                  XC_DOM_PAGE_SHIFT(dom),
                                       PROT_READ | PROT_WRITE,
                                       dom->start_info_seg.pfn);
     if ( start_info == NULL )
@@ -1733,7 +1723,7 @@ static int bootlate_hvm(struct xc_dom_image *dom)
 
     start_info->magic = XEN_HVM_START_MAGIC_VALUE;
 
-    munmap(start_info, start_info_size);
+    munmap(start_info, dom->start_info_seg.pages << XC_DOM_PAGE_SHIFT(dom));
 
     if ( dom->device_model )
     {
--
generated by git-patchbot for /home/xen/git/xen.git#master

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