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Subject[PATCH 02/16] x86/microcode/AMD: Add microcode container verification
Date
From: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>

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(). ]

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Cc: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/3014e96c82cd90761b4601bd2cfe59c4119e46a7.1529424596.git.mail@maciej.szmigiero.name
[ Drop the verify_patch() bits. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/microcode/amd.c | 101 ++++++++++++++++++++++++++++
1 file changed, 101 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index b44c9029860c..36aeb01b3ae8 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -73,6 +73,107 @@ static u16 find_equiv_id(struct equiv_cpu_entry *equiv_table, u32 sig)
return 0;
}

+/*
+ * 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
--
2.19.1
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