Messages in this thread | | | Subject | Re: [PATCH v5 4/6] x86/microcode/AMD: Check microcode container data in the late loader | From | "Maciej S. Szmigiero" <> | Date | Tue, 1 May 2018 00:27:51 +0200 |
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On 30.04.2018 11:05, Borislav Petkov wrote: > On Mon, Apr 23, 2018 at 11:34:09PM +0200, Maciej S. Szmigiero wrote: >> --- a/arch/x86/kernel/cpu/microcode/amd.c >> +++ b/arch/x86/kernel/cpu/microcode/amd.c >> @@ -750,28 +752,20 @@ static int verify_and_add_patch(u8 family, u8 *fw, unsigned int leftover) >> return crnt_size; >> } >> >> - /* >> - * 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 crnt_size; >> - } >> >> patch = kzalloc(sizeof(*patch), GFP_KERNEL); >> if (!patch) { >> pr_err("Patch allocation failure.\n"); >> - return -EINVAL; >> + return 0; > > So by convention returning 0 is success and negative value means error. > I don't see the reason for changing that in the whole code.
1) -EINVAL maps to a valid return value of 4294967274 bytes. We have a different behavior for invalid data in the container file (including too large lengths) than for grave errors like a failed memory allocation.
2) This function single caller (__load_microcode_amd()) normalized any error that verify_and_add_patch() returned to UCODE_ERROR anyway,
3) The existing code uses a convention that zero return value means 'terminate processing' for the parse_container() function in the early loader which normally returns a 'bytes consumed' value, as this function does.
Thanks, Maciej
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