x86/microcode/AMD: Add microcode container verification

Add container and patch verification functions to the AMD microcode
update driver.

These functions check whether a passed buffer contains the relevant
structure, whether it isn't truncated and (for actual microcode patches)
whether the size of a patch is not too large for a particular CPU family.
By adding these checks as separate functions the actual microcode loading
code won't get interspersed with a lot of checks and so will be more
readable.

 [ bp: Make all pr_err() calls into pr_debug() and drop the
   verify_patch() bits. ]

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/3014e96c82cd90761b4601bd2cfe59c4119e46a7.1529424596.git.mail@maciej.szmigiero.name

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index b44c902..36aeb01 100644 (file)
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -74,6 +74,107 @@ static u16 find_equiv_id(struct equiv_cpu_entry *equiv_table, u32 sig)
 }
 
 /*
+ * Check whether there is a valid microcode container file at the beginning
+ * of @buf of size @buf_size. Set @early to use this function in the early path.
+ */
+static bool verify_container(const u8 *buf, size_t buf_size, bool early)
+{
+       u32 cont_magic;
+
+       if (buf_size <= CONTAINER_HDR_SZ) {
+               if (!early)
+                       pr_debug("Truncated microcode container header.\n");
+
+               return false;
+       }
+
+       cont_magic = *(const u32 *)buf;
+       if (cont_magic != UCODE_MAGIC) {
+               if (!early)
+                       pr_debug("Invalid magic value (0x%08x).\n", cont_magic);
+
+               return false;
+       }
+
+       return true;
+}
+
+/*
+ * Check whether there is a valid, non-truncated CPU equivalence table at the
+ * beginning of @buf of size @buf_size. Set @early to use this function in the
+ * early path.
+ */
+static bool verify_equivalence_table(const u8 *buf, size_t buf_size, bool early)
+{
+       const u32 *hdr = (const u32 *)buf;
+       u32 cont_type, equiv_tbl_len;
+
+       if (!verify_container(buf, buf_size, early))
+               return false;
+
+       cont_type = hdr[1];
+       if (cont_type != UCODE_EQUIV_CPU_TABLE_TYPE) {
+               if (!early)
+                       pr_debug("Wrong microcode container equivalence table type: %u.\n",
+                              cont_type);
+
+               return false;
+       }
+
+       buf_size -= CONTAINER_HDR_SZ;
+
+       equiv_tbl_len = hdr[2];
+       if (equiv_tbl_len < sizeof(struct equiv_cpu_entry) ||
+           buf_size < equiv_tbl_len) {
+               if (!early)
+                       pr_debug("Truncated equivalence table.\n");
+
+               return false;
+       }
+
+       return true;
+}
+
+/*
+ * Check whether there is a valid, non-truncated microcode patch section at the
+ * beginning of @buf of size @buf_size. Set @early to use this function in the
+ * early path.
+ */
+static bool verify_patch_section(const u8 *buf, size_t buf_size, bool early)
+{
+       const u32 *hdr;
+       u32 patch_type, patch_size;
+
+       if (buf_size < SECTION_HDR_SIZE) {
+               if (!early)
+                       pr_debug("Truncated patch section.\n");
+
+               return false;
+       }
+
+       hdr = (const u32 *)buf;
+       patch_type = hdr[0];
+       patch_size = hdr[1];
+
+       if (patch_type != UCODE_UCODE_TYPE) {
+               if (!early)
+                       pr_debug("Invalid type field (0x%x) in container file section header.\n",
+                               patch_type);
+
+               return false;
+       }
+
+       if (patch_size < sizeof(struct microcode_header_amd)) {
+               if (!early)
+                       pr_debug("Patch of size %u too short.\n", patch_size);
+
+               return false;
+       }
+
+       return true;
+}
+
+/*
  * This scans the ucode blob for the proper container as we can have multiple
  * containers glued together. Returns the equivalence ID from the equivalence
  * table or 0 if none found.