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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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