[Xen-devel] [PATCH V3] x86, amd_ucode: Verify max allowed patch size before apply

[Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>]

Each family has a stipulated max patch_size. Use this as
additional sanity check before we apply it.

Also, tone down the amount of debug messages and
Follow microcode_intel's implementation of pr_debug.

While at it, fix comment at very top to indicate we support ucode
patch loading from fam10h and higher.

Changes from V2-
 - using microcode_intel way of pr_debug
 - go back to using bool_t for microcode_fits and return 1 for
   Success, 0 for Err as that is what do_microcode_update hypercall
   will expect.

Signed-off-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>
Reviewed-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
---
 xen/arch/x86/microcode_amd.c |   47 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/microcode_amd.c b/xen/arch/x86/microcode_amd.c
index b227173..dfe5f90 100644
--- a/xen/arch/x86/microcode_amd.c
+++ b/xen/arch/x86/microcode_amd.c
@@ -8,7 +8,7 @@
  *  Tigran Aivazian <tigran@xxxxxxxxxxxxxxxxxxxx>
  *
  *  This driver allows to upgrade microcode on AMD
- *  family 0x10 and 0x11 processors.
+ *  family 0x10 and later.
  *
  *  Licensed unter the terms of the GNU General Public
  *  License version 2. See file COPYING for details.
@@ -27,6 +27,8 @@
 #include <asm/microcode.h>
 #include <asm/hvm/svm/svm.h>
 
+#define pr_debug(x...) ((void)0)
+
 struct __packed equiv_cpu_entry {
     uint32_t installed_cpu;
     uint32_t fixed_errata_mask;
@@ -88,12 +90,40 @@ static int collect_cpu_info(int cpu, struct cpu_signature 
*csig)
 
     rdmsrl(MSR_AMD_PATCHLEVEL, csig->rev);
 
-    printk(KERN_DEBUG "microcode: CPU%d collect_cpu_info: patch_id=%#x\n",
+    pr_debug("microcode: CPU%d collect_cpu_info: patch_id=%#x\n",
            cpu, csig->rev);
 
     return 0;
 }
 
+static bool_t verify_patch_size(uint32_t patch_size)
+{
+    uint32_t max_size;
+
+#define F1XH_MPB_MAX_SIZE 2048
+#define F14H_MPB_MAX_SIZE 1824
+#define F15H_MPB_MAX_SIZE 4096
+#define F16H_MPB_MAX_SIZE 3458
+
+    switch (boot_cpu_data.x86)
+    {
+    case 0x14:
+        max_size = F14H_MPB_MAX_SIZE;
+        break;
+    case 0x15:
+        max_size = F15H_MPB_MAX_SIZE;
+        break;
+    case 0x16:
+        max_size = F16H_MPB_MAX_SIZE;
+        break;
+    default:
+        max_size = F1XH_MPB_MAX_SIZE;
+        break;
+    }
+
+    return (patch_size <= max_size);
+}
+
 static bool_t microcode_fits(const struct microcode_amd *mc_amd, int cpu)
 {
     struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu);
@@ -123,10 +153,19 @@ static bool_t microcode_fits(const struct microcode_amd 
*mc_amd, int cpu)
     if ( (mc_header->processor_rev_id) != equiv_cpu_id )
         return 0;
 
+    if ( !verify_patch_size(mc_amd->mpb_size) )
+    {
+        pr_debug("microcode: patch size mismatch\n");
+        return 0;
+    }
+
     if ( mc_header->patch_id <= uci->cpu_sig.rev )
+    {
+        pr_debug("microcode: patch is already at required level or 
greater.\n");
         return 0;
+    }
 
-    printk(KERN_DEBUG "microcode: CPU%d found a matching microcode "
+    pr_debug("microcode: CPU%d found a matching microcode "
            "update with version %#x (current=%#x)\n",
            cpu, mc_header->patch_id, uci->cpu_sig.rev);
 
@@ -224,7 +263,7 @@ static int get_ucode_from_buffer_amd(
 
     *offset = off + mpbuf->len + 8;
 
-    printk(KERN_DEBUG "microcode: CPU%d size %zu, block size %u offset %zu 
equivID %#x rev %#x\n",
+    pr_debug("microcode: CPU%d size %zu, block size %u offset %zu equivID %#x 
rev %#x\n",
            raw_smp_processor_id(), bufsize, mpbuf->len, off,
            ((struct microcode_header_amd *)mc_amd->mpb)->processor_rev_id,
            ((struct microcode_header_amd *)mc_amd->mpb)->patch_id);
-- 
1.7.9.5


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