[PATCH v2] Fix two problems in the microcode parsers

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

The microcode might come from a questionable source, so it is necessary
for the parsers to treat it as untrusted.  The CPU will validate the
microcode before applying it, so loading microcode from unofficial
sources is actually a legitimate thing to do in some cases.

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/cpu/microcode/amd.c   | 6 +++---
 xen/arch/x86/cpu/microcode/intel.c | 7 ++++---
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c
index 
d2a26967c6dbc4695602dd46d5836a6d88e15072..08fe3ac61c18a8e16f694e128973da96ce6995e3
 100644
--- a/xen/arch/x86/cpu/microcode/amd.c
+++ b/xen/arch/x86/cpu/microcode/amd.c
@@ -338,8 +338,7 @@ static struct microcode_patch *cf_check 
cpu_request_microcode(
         if ( size < sizeof(*et) ||
              (et = buf)->type != UCODE_EQUIV_CPU_TABLE_TYPE ||
              size - sizeof(*et) < et->len ||
-             et->len % sizeof(et->eq[0]) ||
-             et->eq[(et->len / sizeof(et->eq[0])) - 1].installed_cpu )
+             et->len % sizeof(et->eq[0]) )
         {
             printk(XENLOG_ERR "microcode: Bad equivalent cpu table\n");
             error = -EINVAL;
@@ -365,7 +364,8 @@ static struct microcode_patch *cf_check 
cpu_request_microcode(
             if ( size < sizeof(*mc) ||
                  (mc = buf)->type != UCODE_UCODE_TYPE ||
                  size - sizeof(*mc) < mc->len ||
-                 mc->len < sizeof(struct microcode_patch) )
+                 mc->len < sizeof(struct microcode_patch) ||
+                 mc->len % 4 != 0 )
             {
                 printk(XENLOG_ERR "microcode: Bad microcode data\n");
                 error = -EINVAL;
diff --git a/xen/arch/x86/cpu/microcode/intel.c 
b/xen/arch/x86/cpu/microcode/intel.c
index 
6f6957058684d7275d62e525e88ff678db9eb6d2..3e113c84b1fff0ba18a0251dbac0c7d6e2b229f6
 100644
--- a/xen/arch/x86/cpu/microcode/intel.c
+++ b/xen/arch/x86/cpu/microcode/intel.c
@@ -149,8 +149,8 @@ static int microcode_sanity_check(const struct 
microcode_patch *patch)
 {
     const struct extended_sigtable *ext;
     const uint32_t *ptr;
-    unsigned int total_size = get_totalsize(patch);
-    unsigned int data_size = get_datasize(patch);
+    uint32_t total_size = get_totalsize(patch);
+    uint32_t data_size = get_datasize(patch);
     unsigned int i, ext_size;
     uint32_t sum;
 
@@ -159,7 +159,8 @@ static int microcode_sanity_check(const struct 
microcode_patch *patch)
      * must fit within it.
      */
     if ( (total_size & 1023) ||
-         data_size > (total_size - MC_HEADER_SIZE) )
+         data_size > (total_size - MC_HEADER_SIZE) ||
+         (data_size % 4) != 0 )
     {
         printk(XENLOG_WARNING "microcode: Bad size\n");
         return -EINVAL;

base-commit: 035baa203b978b219828d0d3c16057beb344f35c
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab