[Xen-devel] [PATCH] xen: arm: Avoid reading beyond the last module

["Chris (Christopher) Brand" <chris.brand@xxxxxxxxxxxx>]

nr_mods is set in add_boot_module() to the number of module
array elements used. This function also ensures that nr_mods
never exceeds MAX_MODULES (the size of the array). When looping
through the array, the correct maximum index is "nr_mods-1",
not "nr_mods". If the array is full, using the latter will in
fact access beyond the end of the array.
This was done correctly in boot_module_find_by_kind() and
consider_modules() but incorrectly in discard_initial_modules()
and next_module().

Signed-off-by: Chris Brand <chris.brand@xxxxxxxxxxxx>
---
 xen/arch/arm/setup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 06f8e54b1f04..5daa6db919ac 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -250,7 +250,7 @@ void __init discard_initial_modules(void)
     struct bootmodules *mi = &bootinfo.modules;
     int i;
 
-    for ( i = 0; i <= mi->nr_mods; i++ )
+    for ( i = 0; i < mi->nr_mods; i++ )
     {
         paddr_t s = mi->module[i].start;
         paddr_t e = s + PAGE_ALIGN(mi->module[i].size);
@@ -350,7 +350,7 @@ static paddr_t __init next_module(paddr_t s, paddr_t *end)
     paddr_t lowest = ~(paddr_t)0;
     int i;
 
-    for ( i = 0; i <= mi->nr_mods; i++ )
+    for ( i = 0; i < mi->nr_mods; i++ )
     {
         paddr_t mod_s = mi->module[i].start;
         paddr_t mod_e = mod_s + mi->module[i].size;
-- 
1.9.1


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