From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3791B2110E; Tue, 27 May 2025 17:06:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748365562; cv=none; b=ewB0k+puoHzqmtLgkji3suSBuStSE0i+7/KSixQaNjAUC05O1rHO3FqRgeqxgGMlsYf5qIne9FZwTw+gCOmWVJraq06ykrCNfjwImjK6rP6Cvxi+KYQwHxx3KvLPYrqaeeqCf/C7s7vKvEnkAYkDAVIvCdsFX6ckKhDM2bn/xLA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748365562; c=relaxed/simple; bh=gcb0TAgudwrHWQKiBz8R3yFrarIYArAFkDH9y72k5EA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uwRWtsmXzNxG/SLrZeDjYuc79/GFuKri200EdNzWzE6UfnIsvQ9GlssNrUtHArihVtGBKIBdzD/tBBSNeWIuP2bntbDcgl6pJxNZuqPfx2rkWlX6KKMZy4e7H4sIm2QUK9jXil7ZF6Vn8wLy3ne2+mHXEwiA/ubR2CsoltLrjzA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=c4z0Zrks; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="c4z0Zrks" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4014C4CEEB; Tue, 27 May 2025 17:06:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1748365562; bh=gcb0TAgudwrHWQKiBz8R3yFrarIYArAFkDH9y72k5EA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c4z0Zrks8KF9K6Ae93fq5PMEFckIxhVvmhvqEHafpU1BSnE0GBMZE7Vhzx8xYFGxW 6si3YzlMqa6hHia+IXeu/0NuMD6VPfoTzTIxyn2FbOjSn726vAnoSD0oa4EFr+KNzp 6nPGkEUAlYteYqpigbec5o6EgyQeYoRtothO1ydc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sami Tolvanen , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 6.12 376/626] x86/ibt: Handle FineIBT in handle_cfi_failure() Date: Tue, 27 May 2025 18:24:29 +0200 Message-ID: <20250527162500.296126196@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250527162445.028718347@linuxfoundation.org> References: <20250527162445.028718347@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra [ Upstream commit 882b86fd4e0d49bf91148dbadcdbece19ded40e6 ] Sami reminded me that FineIBT failure does not hook into the regular CFI failure case, and as such CFI_PERMISSIVE does not work. Reported-by: Sami Tolvanen Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Sami Tolvanen Link: https://lkml.kernel.org/r/20250214092619.GB21726@noisy.programming.kicks-ass.net Signed-off-by: Sasha Levin --- arch/x86/include/asm/cfi.h | 11 +++++++++++ arch/x86/kernel/alternative.c | 30 ++++++++++++++++++++++++++++++ arch/x86/kernel/cfi.c | 22 ++++++++++++++++++---- 3 files changed, 59 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/cfi.h b/arch/x86/include/asm/cfi.h index 31d19c815f992..7dd5ab239c87b 100644 --- a/arch/x86/include/asm/cfi.h +++ b/arch/x86/include/asm/cfi.h @@ -126,6 +126,17 @@ static inline int cfi_get_offset(void) extern u32 cfi_get_func_hash(void *func); +#ifdef CONFIG_FINEIBT +extern bool decode_fineibt_insn(struct pt_regs *regs, unsigned long *target, u32 *type); +#else +static inline bool +decode_fineibt_insn(struct pt_regs *regs, unsigned long *target, u32 *type) +{ + return false; +} + +#endif + #else static inline enum bug_trap_type handle_cfi_failure(struct pt_regs *regs) { diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 66e77bd7d5116..6ab96bc764cfa 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1254,6 +1254,7 @@ asm( ".pushsection .rodata \n" " endbr64 \n" " subl $0x12345678, %r10d \n" " je fineibt_preamble_end \n" + "fineibt_preamble_ud2: \n" " ud2 \n" " nop \n" "fineibt_preamble_end: \n" @@ -1261,9 +1262,11 @@ asm( ".pushsection .rodata \n" ); extern u8 fineibt_preamble_start[]; +extern u8 fineibt_preamble_ud2[]; extern u8 fineibt_preamble_end[]; #define fineibt_preamble_size (fineibt_preamble_end - fineibt_preamble_start) +#define fineibt_preamble_ud2 (fineibt_preamble_ud2 - fineibt_preamble_start) #define fineibt_preamble_hash 7 asm( ".pushsection .rodata \n" @@ -1568,6 +1571,33 @@ static void poison_cfi(void *addr) } } +/* + * regs->ip points to a UD2 instruction, return true and fill out target and + * type when this UD2 is from a FineIBT preamble. + * + * We check the preamble by checking for the ENDBR instruction relative to the + * UD2 instruction. + */ +bool decode_fineibt_insn(struct pt_regs *regs, unsigned long *target, u32 *type) +{ + unsigned long addr = regs->ip - fineibt_preamble_ud2; + u32 endbr, hash; + + __get_kernel_nofault(&endbr, addr, u32, Efault); + if (endbr != gen_endbr()) + return false; + + *target = addr + fineibt_preamble_size; + + __get_kernel_nofault(&hash, addr + fineibt_preamble_hash, u32, Efault); + *type = (u32)regs->r10 + hash; + + return true; + +Efault: + return false; +} + #else static void __apply_fineibt(s32 *start_retpoline, s32 *end_retpoline, diff --git a/arch/x86/kernel/cfi.c b/arch/x86/kernel/cfi.c index e6bf78fac1462..f6905bef0af84 100644 --- a/arch/x86/kernel/cfi.c +++ b/arch/x86/kernel/cfi.c @@ -70,11 +70,25 @@ enum bug_trap_type handle_cfi_failure(struct pt_regs *regs) unsigned long target; u32 type; - if (!is_cfi_trap(regs->ip)) - return BUG_TRAP_TYPE_NONE; + switch (cfi_mode) { + case CFI_KCFI: + if (!is_cfi_trap(regs->ip)) + return BUG_TRAP_TYPE_NONE; + + if (!decode_cfi_insn(regs, &target, &type)) + return report_cfi_failure_noaddr(regs, regs->ip); + + break; - if (!decode_cfi_insn(regs, &target, &type)) - return report_cfi_failure_noaddr(regs, regs->ip); + case CFI_FINEIBT: + if (!decode_fineibt_insn(regs, &target, &type)) + return BUG_TRAP_TYPE_NONE; + + break; + + default: + return BUG_TRAP_TYPE_NONE; + } return report_cfi_failure(regs, regs->ip, &target, type); } -- 2.39.5