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SubjectRe: [PATCH v6 5/8] x86/microcode/AMD: Check microcode container data in the late loader
On Sun, May 20, 2018 at 12:07:19AM +0200, Maciej S. Szmigiero wrote:
> Convert the late loader in the AMD microcode update driver to use newly
> introduced microcode container data checking functions as it was previously
> done for the early loader.
>
> Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
> ---
> arch/x86/kernel/cpu/microcode/amd.c | 70 +++++++++++++----------------
> 1 file changed, 32 insertions(+), 38 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
> index f8bd74341ed8..3e10a5920f58 100644
> --- a/arch/x86/kernel/cpu/microcode/amd.c
> +++ b/arch/x86/kernel/cpu/microcode/amd.c
> @@ -693,28 +693,26 @@ static enum ucode_state apply_microcode_amd(int cpu)
> return UCODE_UPDATED;
> }
>
> -static int install_equiv_cpu_table(const u8 *buf)
> +static unsigned int install_equiv_cpu_table(const u8 *buf, size_t buf_size)
> {
> - unsigned int *ibuf = (unsigned int *)buf;
> - unsigned int type = ibuf[1];
> - unsigned int size = ibuf[2];
> + const u32 *hdr;
> + u32 equiv_tbl_len;
>
> - if (type != UCODE_EQUIV_CPU_TABLE_TYPE || !size) {
> - pr_err("empty section/"
> - "invalid type field in container file section header\n");
> - return -EINVAL;
> - }
> + if (!verify_equivalence_table(buf, buf_size, false))
> + return 0;
> +
> + hdr = (const u32 *)buf;
> + equiv_tbl_len = hdr[2];
>
> - equiv_cpu_table = vmalloc(size);
> + equiv_cpu_table = vmalloc(equiv_tbl_len);
> if (!equiv_cpu_table) {
> pr_err("failed to allocate equivalent CPU table\n");
> - return -ENOMEM;
> + return 0;
> }
>
> - memcpy(equiv_cpu_table, buf + CONTAINER_HDR_SZ, size);
> + memcpy(equiv_cpu_table, buf + CONTAINER_HDR_SZ, equiv_tbl_len);
>
> - /* add header length */
> - return size + CONTAINER_HDR_SZ;
> + return equiv_tbl_len;
> }
>
> static void free_equiv_cpu_table(void)
> @@ -739,13 +737,19 @@ static void cleanup(void)
> static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover,
> unsigned int *crnt_size)
> {
> + u32 *hdr = (u32 *)fw;
> struct microcode_header_amd *mc_hdr;
> struct ucode_patch *patch;
> - unsigned int patch_size, ret;
> + u32 patch_size;
> u32 proc_fam;
> u16 proc_id;
>
> - patch_size = *(u32 *)(fw + 4);
> + if (!verify_patch_section(fw, leftover, false)) {
> + *crnt_size = leftover;

I'm not sure about this: we verify the patch section and in the error
case we skip over the whole leftover buffer?

Maybe skipping over SECTION_HDR_SIZE or better yet skip 1 byte here
too, like in parse_container() to give us the highest chance of finding
something sensible later...

> + return 0;
> + }
> +
> + patch_size = hdr[1];

Same comment as before: verify_patch_size()

But I think you can simply do verify_patch() at the beginning of the
function and be done with the verification in that function.

> *crnt_size = patch_size + SECTION_HDR_SIZE;
> mc_hdr = (struct microcode_header_amd *)(fw + SECTION_HDR_SIZE);
> proc_id = mc_hdr->processor_rev_id;
> @@ -767,16 +771,8 @@ static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover,
> return 0;
> }
>
> - /*
> - * The section header length is not included in this indicated size
> - * but is present in the leftover file length so we need to subtract
> - * it before passing this value to the function below.
> - */
> - ret = verify_patch_size(family, patch_size, leftover - SECTION_HDR_SIZE);
> - if (!ret) {
> - pr_err("Patch-ID 0x%08x: size mismatch.\n", mc_hdr->patch_id);
> + if (!verify_patch(family, fw, leftover, false))
> return 0;
> - }
>
> patch = kzalloc(sizeof(*patch), GFP_KERNEL);
> if (!patch) {
> @@ -810,21 +806,21 @@ static enum ucode_state __load_microcode_amd(u8 family, const u8 *data,
> enum ucode_state ret = UCODE_ERROR;
> unsigned int leftover;
> u8 *fw = (u8 *)data;
> - int offset;
> + unsigned int offset;
>
> - offset = install_equiv_cpu_table(data);
> - if (offset < 0) {
> + offset = install_equiv_cpu_table(data, size);
> + if (!offset) {
> pr_err("failed to create equivalent cpu table\n");

No need for that error message anymore I guess -
install_equiv_cpu_table() and verify_equivalence_table() are pretty
vocal in the error case already.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--

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