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 <m...@maciej.szmigiero.name> --- arch/x86/kernel/cpu/microcode/amd.c | 148 +++++++++++++++++++++++++++- 1 file changed, 145 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c index dc8ea9a9d962..f9485ff7183c 100644 --- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -73,6 +73,150 @@ static u16 find_equiv_id(struct equiv_cpu_entry *equiv_table, u32 sig) return 0; } +/* + * Checks whether there is a valid microcode container file at the beginning + * of a passed buffer @buf of size @size. + * If @early is set this function does not print errors which makes it + * 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; +} + +/* + * Checks whether there is a valid, non-truncated CPU equivalence table + * at the beginning of a passed buffer @buf of size @size. + * If @early is set this function does not print errors which makes it + * 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; +} + +/* + * Checks whether there is a valid, non-truncated microcode patch section + * at the beginning of a passed buffer @buf of size @size. + * If @early is set this function does not print errors which makes it + * usable by the early microcode loader. + */ +static bool verify_patch_section(const u8 *buf, size_t buf_size, bool early) +{ + const u32 *hdr = (const u32 *)buf; + u32 patch_type, patch_size; + + if (buf_size < SECTION_HDR_SIZE) { + if (!early) + pr_err("Truncated patch section.\n"); + + return false; + } + + 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; + } + + if (buf_size - SECTION_HDR_SIZE < patch_size) { + if (!early) + pr_err("Patch of size %u truncated.\n", patch_size); + + return false; + } + + return true; +} + +static unsigned int verify_patch_size(u8 family, u32 patch_size, + unsigned int size); + +/* + * Checks whether a microcode patch located at the beginning of a passed + * buffer @buf of size @size is not too large for a particular @family + * and is not truncated. + * If @early is set this function does not print errors which makes it + * usable by the early microcode loader. + */ +static bool verify_patch(u8 family, const u8 *buf, size_t buf_size, bool early) +{ + const u32 *hdr = (const u32 *)buf; + u32 patch_size; + + if (!verify_patch_section(buf, buf_size, early)) + return false; + + patch_size = hdr[1]; + + /* + * 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 +638,8 @@ 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; }