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

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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: ec400ddeff ("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
This commit is contained in:
Chen Yu 2020-11-13 09:59:23 +08:00 committed by Borislav Petkov
parent 8986f223bd
commit 1a371e67dc
1 changed files with 10 additions and 53 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
arch/x86/kernel/cpu/microcode/intel.c
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@ -100,53 +100,6 @@ 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;
@ -164,7 +117,7 @@ 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;
@ -210,6 +163,9 @@ 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
@ -344,13 +300,14 @@ 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;
}
@ -483,14 +440,14 @@ 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);
@ -935,7 +892,7 @@ static enum ucode_state generic_load_microcode(int cpu, struct iov_iter *iter)
* 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);