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>

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index c6826d1e8082584268d1b5e8f3abeb176ee61187..746e7fd08aad7082747ee1d9dca80570f1a00e3b 100644 (file)
--- 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 5e109a31f62bb0168f704bd04d725b8ff580df6e..420eb933189ca487110607475ddbf33be8e8267b 100644 (file)
--- 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);