From patchwork Mon Oct 14 16:11:00 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 13835310 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 67EDCD1812D for ; Mon, 14 Oct 2024 16:12:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=llp5ytVzB4Ph0+/8a8EaRdT3yelYdQ+lkHdacYEmEGg=; b=iObgzfLDLjM0x7t+KTDOFzAZne OeBXyvtxesYCqqueXcu5VtKfE9fLOVWH7eV0+tDZniugcXyIl5KcLdPk8guqyggSuc/KXEvP/28AW 5DKumJ+/Yyg+HEVVUAu0PBUUE00J2T319cpUuHfnTPzRDXFvkoa2xNlKttr7EE8VTWFTI6563rlu3 fAFjYWgMAWggWJpTn1du7Z2hIYyCpankH02vZ33gxTbGyoRvzxPuuDcOCYIurIeeUyImH9P5L1yPu IQnefBe6Ra93rM3962NouFeQNUvpfKxibosYooW8rHgehuR38yN5E5s6Gt/Dbd+6OGmF3uuk/iZbA vexIZkXQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1t0NgW-00000005oyL-0Ol3; Mon, 14 Oct 2024 16:12:40 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1t0Nf4-00000005obx-36LV for linux-arm-kernel@lists.infradead.org; Mon, 14 Oct 2024 16:11:12 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 174665C4BEB; Mon, 14 Oct 2024 16:11:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5CA5DC4CEC3; Mon, 14 Oct 2024 16:11:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728922269; bh=wOqrwTp34LIuaLxXUWvsvqtFruSD5VEeAEnaub7ceTs=; h=From:To:Cc:Subject:Date:From; b=D/Adz256Xdf+mrawykJtzhVASiYOfpa0IwX3FMvxrVz2YweLRVFW9jxuHDfqhmAud EX/OfDsT5YcKIAt0/0jYU0pRGqdgAIXbHl2iDM4yTBThMGKRnrzyXJPGkhlZgKI+me G1GiX6e1gC/3Y6UPKg9hP7jrx1mLr9lfzhgSG+BNeWl3nTlifrrUMJEPcI7jsYzATM Om6l6jV/DUaW4S//gG5cRdcklwg52DsYh1Hgu2Xjt4nDQORIgC0mGjwF9c+LM5GmhZ 0njUvD9G/zEeDzfw0qAWsL15P2l4h+lkH2c5WWZJvG/7faEwSwnrsshKuzR1GDRqpW e82VDWBrynuSA== From: Will Deacon To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, ryabinin.a.a@gmail.com, glider@google.com, kasan-dev@googlegroups.com, Will Deacon , Andrey Konovalov , Mark Rutland , syzbot+908886656a02769af987@syzkaller.appspotmail.com Subject: [PATCH] kasan: Disable Software Tag-Based KASAN with GCC Date: Mon, 14 Oct 2024 17:11:00 +0100 Message-Id: <20241014161100.18034-1-will@kernel.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241014_091110_883454_17477724 X-CRM114-Status: GOOD ( 15.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Syzbot reports a KASAN failure early during boot on arm64 when building with GCC 12.2.0 and using the Software Tag-Based KASAN mode: | BUG: KASAN: invalid-access in smp_build_mpidr_hash arch/arm64/kernel/setup.c:133 [inline] | BUG: KASAN: invalid-access in setup_arch+0x984/0xd60 arch/arm64/kernel/setup.c:356 | Write of size 4 at addr 03ff800086867e00 by task swapper/0 | Pointer tag: [03], memory tag: [fe] Initial triage indicates that the report is a false positive and a thorough investigation of the crash by Mark Rutland revealed the root cause to be a bug in GCC: > When GCC is passed `-fsanitize=hwaddress` or > `-fsanitize=kernel-hwaddress` it ignores > `__attribute__((no_sanitize_address))`, and instruments functions > we require are not instrumented. > > [...] > > All versions [of GCC] I tried were broken, from 11.3.0 to 14.2.0 > inclusive. > > I think we have to disable KASAN_SW_TAGS with GCC until this is > fixed Disable Software Tag-Based KASAN when building with GCC by making CC_HAS_KASAN_SW_TAGS depend on !CC_IS_GCC. Cc: Andrey Konovalov Suggested-by: Mark Rutland Reported-by: syzbot+908886656a02769af987@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/000000000000f362e80620e27859@google.com Link: https://lore.kernel.org/r/ZvFGwKfoC4yVjN_X@J2N7QTR9R3 Link: https://bugzilla.kernel.org/show_bug.cgi?id=218854 Signed-off-by: Will Deacon Acked-by: Mark Rutland Reviewed-by: Andrey Konovalov Reported-by: syzbot+908886656a02769af987@syzkaller.appspotmail.com Signed-off-by: Marco Elver --- lib/Kconfig.kasan | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) While sweeping up pending fixes and open bug reports, I noticed this one had slipped through the cracks... diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index 98016e137b7f..233ab2096924 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -22,8 +22,11 @@ config ARCH_DISABLE_KASAN_INLINE config CC_HAS_KASAN_GENERIC def_bool $(cc-option, -fsanitize=kernel-address) +# GCC appears to ignore no_sanitize_address when -fsanitize=kernel-hwaddress +# is passed. See https://bugzilla.kernel.org/show_bug.cgi?id=218854 (and +# the linked LKML thread) for more details. config CC_HAS_KASAN_SW_TAGS - def_bool $(cc-option, -fsanitize=kernel-hwaddress) + def_bool !CC_IS_GCC && $(cc-option, -fsanitize=kernel-hwaddress) # This option is only required for software KASAN modes. # Old GCC versions do not have proper support for no_sanitize_address. @@ -98,7 +101,7 @@ config KASAN_SW_TAGS help Enables Software Tag-Based KASAN. - Requires GCC 11+ or Clang. + Requires Clang. Supported only on arm64 CPUs and relies on Top Byte Ignore.