Messages in this thread Patch in this message | | | From | "Maciej S. Szmigiero" <> | Subject | [PATCH v7 2/9] x86/microcode/AMD: Add microcode container data checking functions | Date | Tue, 19 Jun 2018 20:47:32 +0200 |
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Add verify_container(), verify_equivalence_table(), verify_patch_section() and verify_patch() 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.
Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name> --- arch/x86/kernel/cpu/microcode/amd.c | 180 +++++++++++++++++++++++++++- 1 file changed, 177 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c index dc8ea9a9d962..120778771909 100644 --- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -73,6 +73,182 @@ 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 a passed buffer @buf of size @buf_size. + * If @early is set do not print errors so this function is usable by the + * early microcode loader. + */ +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_err("Truncated microcode container header.\n"); + + return false; + } + + cont_magic = *(const u32 *)buf; + if (cont_magic != UCODE_MAGIC) { + if (!early) + pr_err("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 a passed buffer @buf of size @buf_size. + * If @early is set do not print errors so this function is usable by the + * early microcode loader. + */ +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_err("Wrong microcode container equivalence table type: %u.\n", + cont_type); + + return false; + } + + equiv_tbl_len = hdr[2]; + if (equiv_tbl_len < sizeof(struct equiv_cpu_entry) || + buf_size - CONTAINER_HDR_SZ < equiv_tbl_len) { + if (!early) + pr_err("Truncated equivalence table.\n"); + + return false; + } + + return true; +} + +/* + * Check whether there is a valid, non-truncated microcode patch section + * at the beginning of a passed buffer @buf of size @buf_size. + * If @early is set do not print errors so this function is usable by the + * early microcode loader. + */ +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_err("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_err("Invalid type field (%u) in container file section header.\n", + patch_type); + + return false; + } + + if (patch_size < sizeof(struct microcode_header_amd)) { + if (!early) + pr_err("Patch of size %u too short.\n", patch_size); + + return false; + } + + return true; +} + +static unsigned int verify_patch_size(u8 family, u32 patch_size, + unsigned int size); + +/* + * Check whether there is a valid, non-truncated microcode patch of the + * right size for a particular family @family at the beginning of a passed + * buffer @buf, buffer that is of size @buf_size. + * Will return the length of current patch data in @crnt_size (even on + * failure), so the caller knows how many bytes it should skip. + * If @early is set do not print errors so this function is usable by the + * early microcode loader. + */ +static bool verify_patch(u8 family, const u8 *buf, size_t buf_size, + unsigned int *crnt_size, bool early) +{ + const u32 *hdr; + u32 patch_size; + const struct microcode_header_amd *mc_hdr; + u8 patch_fam; + + if (!verify_patch_section(buf, buf_size, early)) { + *crnt_size = min_t(unsigned int, 1, buf_size); + return false; + } + + hdr = (const u32 *)buf; + patch_size = hdr[1]; + + if (buf_size - SECTION_HDR_SIZE < patch_size) { + if (!early) + pr_err("Patch of size %u truncated.\n", patch_size); + + *crnt_size = buf_size; + return false; + } + + /* + * Set a patch length limit of slightly less than U32_MAX to + * prevent overflowing 32-bit variables holding the whole + * patch section size. + */ + if (patch_size > U32_MAX - SECTION_HDR_SIZE) { + if (!early) + pr_err("Patch of size %u too large.\n", patch_size); + + *crnt_size = SECTION_HDR_SIZE + PATCH_MAX_SIZE; + return false; + } + + *crnt_size = SECTION_HDR_SIZE + patch_size; + + mc_hdr = (const struct microcode_header_amd *)(buf + SECTION_HDR_SIZE); + patch_fam = 0xf + (mc_hdr->processor_rev_id >> 12); + + /* Is the patch for the proper CPU family? */ + if (family != patch_fam) + return false; + + /* + * 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. + */ + if (!verify_patch_size(family, patch_size, buf_size - SECTION_HDR_SIZE)) { + if (!early) + pr_err("Patch of size %u too large.\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 @@ -494,10 +670,8 @@ static unsigned int verify_patch_size(u8 family, u32 patch_size, unsigned int si break; } - if (patch_size > min_t(u32, size, max_size)) { - pr_err("patch size mismatch\n"); + if (patch_size > min_t(u32, size, max_size)) return 0; - } return patch_size; }
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