x86/microcode/intel: Check patch signature before saving microcode for early loading

commit 1a371e67dc77125736cc56d3a0893f06b75855b6 upstream.

Currently, scan_microcode() leverages microcode_matches() to check
if the microcode matches the CPU by comparing the family and model.
However, the processor stepping and flags of the microcode signature
should also be considered when saving a microcode patch for early
update.

Use find_matching_signature() in scan_microcode() and get rid of the
now-unused microcode_matches() which is a good cleanup in itself.

Complete the verification of the patch being saved for early loading in
save_microcode_patch() directly. This needs to be done there too because
save_mc_for_early() will call save_microcode_patch() too.

The second reason why this needs to be done is because the loader still
tries to support, at least hypothetically, mixed-steppings systems and
thus adds all patches to the cache that belong to the same CPU model
albeit with different steppings.

For example:

  microcode: CPU: sig=0x906ec, pf=0x2, rev=0xd6
  microcode: mc_saved[0]: sig=0x906e9, pf=0x2a, rev=0xd6, total size=0x19400, date = 2020-04-23
  microcode: mc_saved[1]: sig=0x906ea, pf=0x22, rev=0xd6, total size=0x19000, date = 2020-04-27
  microcode: mc_saved[2]: sig=0x906eb, pf=0x2, rev=0xd6, total size=0x19400, date = 2020-04-23
  microcode: mc_saved[3]: sig=0x906ec, pf=0x22, rev=0xd6, total size=0x19000, date = 2020-04-27
  microcode: mc_saved[4]: sig=0x906ed, pf=0x22, rev=0xd6, total size=0x19400, date = 2020-04-23

The patch which is being saved for early loading, however, can only be
the one which fits the CPU this runs on so do the signature verification
before saving.

 [ bp: Do signature verification in save_microcode_patch()
       and rewrite commit message. ]

Fixes: ec400ddeff20 ("x86/microcode_intel_early.c: Early update ucode on Intel's CPU")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=208535
Link: https://lkml.kernel.org/r/20201113015923.13960-1-yu.c.chen@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 16936a24795c8457b789f7b428216cfc5bd1fb4e..3aa0e5a453030cf85452ae023f631c9cd204444e 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -103,53 +103,6 @@ static int has_newer_microcode(void *mc, unsigned int csig, int cpf, int new_rev
        return find_matching_signature(mc, csig, cpf);
 }
 
-/*
- * Given CPU signature and a microcode patch, this function finds if the
- * microcode patch has matching family and model with the CPU.
- *
- * %true - if there's a match
- * %false - otherwise
- */
-static bool microcode_matches(struct microcode_header_intel *mc_header,
-                             unsigned long sig)
-{
-       unsigned long total_size = get_totalsize(mc_header);
-       unsigned long data_size = get_datasize(mc_header);
-       struct extended_sigtable *ext_header;
-       unsigned int fam_ucode, model_ucode;
-       struct extended_signature *ext_sig;
-       unsigned int fam, model;
-       int ext_sigcount, i;
-
-       fam   = x86_family(sig);
-       model = x86_model(sig);
-
-       fam_ucode   = x86_family(mc_header->sig);
-       model_ucode = x86_model(mc_header->sig);
-
-       if (fam == fam_ucode && model == model_ucode)
-               return true;
-
-       /* Look for ext. headers: */
-       if (total_size <= data_size + MC_HEADER_SIZE)
-               return false;
-
-       ext_header   = (void *) mc_header + data_size + MC_HEADER_SIZE;
-       ext_sig      = (void *)ext_header + EXT_HEADER_SIZE;
-       ext_sigcount = ext_header->count;
-
-       for (i = 0; i < ext_sigcount; i++) {
-               fam_ucode   = x86_family(ext_sig->sig);
-               model_ucode = x86_model(ext_sig->sig);
-
-               if (fam == fam_ucode && model == model_ucode)
-                       return true;
-
-               ext_sig++;
-       }
-       return false;
-}
-
 static struct ucode_patch *memdup_patch(void *data, unsigned int size)
 {
        struct ucode_patch *p;
@@ -167,7 +120,7 @@ static struct ucode_patch *memdup_patch(void *data, unsigned int size)
        return p;
 }
 
-static void save_microcode_patch(void *data, unsigned int size)
+static void save_microcode_patch(struct ucode_cpu_info *uci, void *data, unsigned int size)
 {
        struct microcode_header_intel *mc_hdr, *mc_saved_hdr;
        struct ucode_patch *iter, *tmp, *p = NULL;
@@ -213,6 +166,9 @@ static void save_microcode_patch(void *data, unsigned int size)
        if (!p)
                return;
 
+       if (!find_matching_signature(p->data, uci->cpu_sig.sig, uci->cpu_sig.pf))
+               return;
+
        /*
         * Save for early loading. On 32-bit, that needs to be a physical
         * address as the APs are running from physical addresses, before
@@ -347,13 +303,14 @@ scan_microcode(void *data, size_t size, struct ucode_cpu_info *uci, bool save)
 
                size -= mc_size;
 
-               if (!microcode_matches(mc_header, uci->cpu_sig.sig)) {
+               if (!find_matching_signature(data, uci->cpu_sig.sig,
+                                            uci->cpu_sig.pf)) {
                        data += mc_size;
                        continue;
                }
 
                if (save) {
-                       save_microcode_patch(data, mc_size);
+                       save_microcode_patch(uci, data, mc_size);
                        goto next;
                }
 
@@ -486,14 +443,14 @@ static void show_saved_mc(void)
  * Save this microcode patch. It will be loaded early when a CPU is
  * hot-added or resumes.
  */
-static void save_mc_for_early(u8 *mc, unsigned int size)
+static void save_mc_for_early(struct ucode_cpu_info *uci, u8 *mc, unsigned int size)
 {
        /* Synchronization during CPU hotplug. */
        static DEFINE_MUTEX(x86_cpu_microcode_mutex);
 
        mutex_lock(&x86_cpu_microcode_mutex);
 
-       save_microcode_patch(mc, size);
+       save_microcode_patch(uci, mc, size);
        show_saved_mc();
 
        mutex_unlock(&x86_cpu_microcode_mutex);
@@ -937,7 +894,7 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
         * permanent memory. So it will be loaded early when a CPU is hot added
         * or resumes.
         */
-       save_mc_for_early(new_mc, new_mc_size);
+       save_mc_for_early(uci, new_mc, new_mc_size);
 
        pr_debug("CPU%d found a matching microcode update with version 0x%x (current=0x%x)\n",
                 cpu, new_rev, uci->cpu_sig.rev);