x86/microcode/intel: Handle truncated microcode images more robustly

We do not check the input data bounds containing the microcode before
copying a struct microcode_intel_header from it. A specially crafted
microcode could cause the kernel to read invalid memory and lead to a
denial-of-service.

Signed-off-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1422964824-22056-3-git-send-email-quentin.casasnovas@oracle.com
[ Made error message differ from the next one and flipped comparison. ]
Signed-off-by: Borislav Petkov <bp@suse.de>

2 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index c6826d1e8082..746e7fd08aad 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -196,6 +196,11 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
                 struct microcode_header_intel mc_header;
                 unsigned int mc_size;
 
+                if (leftover < sizeof(mc_header)) {
+                        pr_err("error! Truncated header in microcode data file\n");
+                        break;
+                }
+
                 if (get_ucode_data(&mc_header, ucode_ptr, sizeof(mc_header)))
                         break;
 
diff --git a/arch/x86/kernel/cpu/microcode/intel_early.c b/arch/x86/kernel/cpu/microcode/intel_early.c
index 5e109a31f62b..420eb933189c 100644
--- a/arch/x86/kernel/cpu/microcode/intel_early.c
+++ b/arch/x86/kernel/cpu/microcode/intel_early.c
@@ -322,6 +322,10 @@ get_matching_model_microcode(int cpu, unsigned long start,
         int i;
 
         while (leftover && mc_saved_count < ARRAY_SIZE(mc_saved_tmp)) {
+
+                if (leftover < sizeof(mc_header))
+                        break;
+
                 mc_header = (struct microcode_header_intel *)ucode_ptr;
 
                 mc_size = get_totalsize(mc_header);