[PATCH 1/2] x86/MCE/AMD: Cache SMCA MISC block addresses

[Borislav Petkov]

From: Borislav Petkov <b...@suse.de>

... 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.

Reported-by: Johannes Hirte <johannes.hi...@datenkhaos.de>
Signed-off-by: Borislav Petkov <b...@suse.de>
Cc: Yazen Ghannam <yazen.ghan...@amd.com>
Fixes: 27bd59502702 ("x86/mce/AMD: Get address from already initialized block")
Link: http://lkml.kernel.org/r/20180414004230.GA2033@probook
---
 arch/x86/kernel/cpu/mcheck/mce_amd.c | 29 ++++++++++++++--------------
 1 file 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);
 
-- 
2.17.0.391.g1f1cddd558b5

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 
(AG Nürnberg)
--