From patchwork Fri May 13 14:23:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 572510 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE1F6C433FE for ; Fri, 13 May 2022 14:31:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381007AbiEMObt (ORCPT ); Fri, 13 May 2022 10:31:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381198AbiEMObK (ORCPT ); Fri, 13 May 2022 10:31:10 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A54A0985B0; Fri, 13 May 2022 07:28:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 192EECE3237; Fri, 13 May 2022 14:28:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 274EEC36AF2; Fri, 13 May 2022 14:28:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1652452118; bh=VkPUj72UpbJFCY22ks6F56UqOwRU9wtq4zC3+pJvIkk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tx5aNeJVZeHXIUwxHEksjaepFAIWmBSsQ0/qtuhqyxm2A+A4XQetsgdY/q899uylz AcokfPIrS2Jb1z3uZfXA3b9WWJYKrWK0CQ8XYF0N13eEyoZDh7/YVailUAuvOqtsbD HQ5YpYnR9FXCSwyOfvfbH9zZmOqTA5bYCUG0rdl8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Borislav Petkov , Sasha Levin Subject: [PATCH 5.15 05/21] x86/alternative: Relax text_poke_bp() constraint Date: Fri, 13 May 2022 16:23:47 +0200 Message-Id: <20220513142230.035244880@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220513142229.874949670@linuxfoundation.org> References: <20220513142229.874949670@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peter Zijlstra [ Upstream commit 26c44b776dba4ac692a0bf5a3836feb8a63fea6b ] Currently, text_poke_bp() is very strict to only allow patching a single instruction; however with straight-line-speculation it will be required to patch: ret; int3, which is two instructions. As such, relax the constraints a little to allow int3 padding for all instructions that do not imply the execution of the next instruction, ie: RET, JMP.d8 and JMP.d32. While there, rename the text_poke_loc::rel32 field to ::disp. Note: this fills up the text_poke_loc structure which is now a round 16 bytes big. [ bp: Put comments ontop instead of on the side. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20211204134908.082342723@infradead.org Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/alternative.c | 49 +++++++++++++++++++++++++++++------------- 1 file changed, 34 insertions(+), 15 deletions(-) --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -930,10 +930,13 @@ void text_poke_sync(void) } struct text_poke_loc { - s32 rel_addr; /* addr := _stext + rel_addr */ - s32 rel32; + /* addr := _stext + rel_addr */ + s32 rel_addr; + s32 disp; + u8 len; u8 opcode; const u8 text[POKE_MAX_OPCODE_SIZE]; + /* see text_poke_bp_batch() */ u8 old; }; @@ -948,7 +951,8 @@ static struct bp_patching_desc *bp_desc; static __always_inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp) { - struct bp_patching_desc *desc = __READ_ONCE(*descp); /* rcu_dereference */ + /* rcu_dereference */ + struct bp_patching_desc *desc = __READ_ONCE(*descp); if (!desc || !arch_atomic_inc_not_zero(&desc->refs)) return NULL; @@ -982,7 +986,7 @@ noinstr int poke_int3_handler(struct pt_ { struct bp_patching_desc *desc; struct text_poke_loc *tp; - int len, ret = 0; + int ret = 0; void *ip; if (user_mode(regs)) @@ -1022,8 +1026,7 @@ noinstr int poke_int3_handler(struct pt_ goto out_put; } - len = text_opcode_size(tp->opcode); - ip += len; + ip += tp->len; switch (tp->opcode) { case INT3_INSN_OPCODE: @@ -1038,12 +1041,12 @@ noinstr int poke_int3_handler(struct pt_ break; case CALL_INSN_OPCODE: - int3_emulate_call(regs, (long)ip + tp->rel32); + int3_emulate_call(regs, (long)ip + tp->disp); break; case JMP32_INSN_OPCODE: case JMP8_INSN_OPCODE: - int3_emulate_jmp(regs, (long)ip + tp->rel32); + int3_emulate_jmp(regs, (long)ip + tp->disp); break; default: @@ -1118,7 +1121,7 @@ static void text_poke_bp_batch(struct te */ for (do_sync = 0, i = 0; i < nr_entries; i++) { u8 old[POKE_MAX_OPCODE_SIZE] = { tp[i].old, }; - int len = text_opcode_size(tp[i].opcode); + int len = tp[i].len; if (len - INT3_INSN_SIZE > 0) { memcpy(old + INT3_INSN_SIZE, @@ -1195,21 +1198,37 @@ static void text_poke_loc_init(struct te const void *opcode, size_t len, const void *emulate) { struct insn insn; - int ret; + int ret, i; memcpy((void *)tp->text, opcode, len); if (!emulate) emulate = opcode; ret = insn_decode_kernel(&insn, emulate); - BUG_ON(ret < 0); - BUG_ON(len != insn.length); tp->rel_addr = addr - (void *)_stext; + tp->len = len; tp->opcode = insn.opcode.bytes[0]; switch (tp->opcode) { + case RET_INSN_OPCODE: + case JMP32_INSN_OPCODE: + case JMP8_INSN_OPCODE: + /* + * Control flow instructions without implied execution of the + * next instruction can be padded with INT3. + */ + for (i = insn.length; i < len; i++) + BUG_ON(tp->text[i] != INT3_INSN_OPCODE); + break; + + default: + BUG_ON(len != insn.length); + }; + + + switch (tp->opcode) { case INT3_INSN_OPCODE: case RET_INSN_OPCODE: break; @@ -1217,7 +1236,7 @@ static void text_poke_loc_init(struct te case CALL_INSN_OPCODE: case JMP32_INSN_OPCODE: case JMP8_INSN_OPCODE: - tp->rel32 = insn.immediate.value; + tp->disp = insn.immediate.value; break; default: /* assume NOP */ @@ -1225,13 +1244,13 @@ static void text_poke_loc_init(struct te case 2: /* NOP2 -- emulate as JMP8+0 */ BUG_ON(memcmp(emulate, x86_nops[len], len)); tp->opcode = JMP8_INSN_OPCODE; - tp->rel32 = 0; + tp->disp = 0; break; case 5: /* NOP5 -- emulate as JMP32+0 */ BUG_ON(memcmp(emulate, x86_nops[len], len)); tp->opcode = JMP32_INSN_OPCODE; - tp->rel32 = 0; + tp->disp = 0; break; default: /* unknown instruction */