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Message-ID: <20231003-strncpy-arch-x86-coco-tdx-tdx-c-v2-1-0bd21174a217@google.com> Date: Tue, 03 Oct 2023 21:54:59 +0000 From: Justin Stitt <justinstitt@...gle.com> To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com> Cc: linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, Kees Cook <keescook@...omium.org>, Justin Stitt <justinstitt@...gle.com> Subject: [PATCH v2] x86/tdx: replace deprecated strncpy with strtomem_pad strncpy works perfectly here in all cases, however, it is deprecated and as such we should prefer more robust and less ambiguous string apis. Let's use `strtomem_pad` as this matches the functionality of `strncpy` and is _not_ deprecated. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@...r.kernel.org Cc: Kees Cook <keescook@...omium.org> Signed-off-by: Justin Stitt <justinstitt@...gle.com> --- Changes in v2: - update subject (thanks Kees) - update commit message (thanks Dave) - rebase onto mainline cbf3a2cb156a2c91 - Link to v1: https://lore.kernel.org/r/20230911-strncpy-arch-x86-coco-tdx-tdx-c-v1-1-4b38155727f3@google.com --- Note: build-tested Note: Ingo Molnar has some concerns about the comment being out of sync [1] but I believe the comment still has a place as we can still theoretically copy 64 bytes into our destination buffer without a NUL-byte. The extra information about the 65th byte being NUL may serve helpful to future travelers of this code. What do we think? I can drop the comment in a v3 if needed. [1]: https://lore.kernel.org/all/ZRc+JqO7XvyHg%2FnB@gmail.com/ --- arch/x86/coco/tdx/tdx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 1d6b863c42b0..2e1be592c220 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -119,7 +119,7 @@ static void __noreturn tdx_panic(const char *msg) } message; /* VMM assumes '\0' in byte 65, if the message took all 64 bytes */ - strncpy(message.str, msg, 64); + strtomem_pad(message.str, msg, '\0'); args.r8 = message.r8; args.r9 = message.r9; --- base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2 change-id: 20230911-strncpy-arch-x86-coco-tdx-tdx-c-98b0b966bb8d Best regards, -- Justin Stitt <justinstitt@...gle.com>
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