x86/MCE/AMD: Cache SMCA MISC block addresses

... into a global, two-dimensional array and service subsequent reads from
that cache to avoid rdmsr_on_cpu() calls during CPU hotplug (IPIs with IRQs
disabled).

In addition, this fixes a KASAN slab-out-of-bounds read due to wrong usage
of the bank->blocks pointer.

Fixes: 27bd59502702 ("x86/mce/AMD: Get address from already initialized block")
Reported-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Tested-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Yazen Ghannam <yazen.ghannam@amd.com>
Link: http://lkml.kernel.org/r/20180414004230.GA2033@probook

1 files changed, 14 insertions, 15 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index f7666eef4a87..c8e038800591 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -94,6 +94,11 @@ static struct smca_bank_name smca_names[] = {
         [SMCA_SMU]      = { "smu",              "System Management Unit" },
 };
 
+static u32 smca_bank_addrs[MAX_NR_BANKS][NR_BLOCKS] __ro_after_init =
+{
+        [0 ... MAX_NR_BANKS - 1] = { [0 ... NR_BLOCKS - 1] = -1 }
+};
+
 const char *smca_get_name(enum smca_bank_types t)
 {
         if (t >= N_SMCA_BANK_TYPES)
@@ -443,20 +448,26 @@ static u32 smca_get_block_address(unsigned int cpu, unsigned int bank,
         if (!block)
                 return MSR_AMD64_SMCA_MCx_MISC(bank);
 
+        /* Check our cache first: */
+        if (smca_bank_addrs[bank][block] != -1)
+                return smca_bank_addrs[bank][block];
+
         /*
          * For SMCA enabled processors, BLKPTR field of the first MISC register
          * (MCx_MISC0) indicates presence of additional MISC regs set (MISC1-4).
          */
         if (rdmsr_safe_on_cpu(cpu, MSR_AMD64_SMCA_MCx_CONFIG(bank), &low, &high))
-                return addr;
+                goto out;
 
         if (!(low & MCI_CONFIG_MCAX))
-                return addr;
+                goto out;
 
         if (!rdmsr_safe_on_cpu(cpu, MSR_AMD64_SMCA_MCx_MISC(bank), &low, &high) &&
             (low & MASK_BLKPTR_LO))
-                return MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
+                addr = MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1);
 
+out:
+        smca_bank_addrs[bank][block] = addr;
         return addr;
 }
 
@@ -468,18 +479,6 @@ static u32 get_block_address(unsigned int cpu, u32 current_addr, u32 low, u32 hi
         if ((bank >= mca_cfg.banks) || (block >= NR_BLOCKS))
                 return addr;
 
-        /* Get address from already initialized block. */
-        if (per_cpu(threshold_banks, cpu)) {
-                struct threshold_bank *bankp = per_cpu(threshold_banks, cpu)[bank];
-
-                if (bankp && bankp->blocks) {
-                        struct threshold_block *blockp = &bankp->blocks[block];
-
-                        if (blockp)
-                                return blockp->address;
-                }
-        }
-
         if (mce_flags.smca)
                 return smca_get_block_address(cpu, bank, block);