From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7141C76188 for ; Fri, 19 Jul 2019 05:53:35 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2665D2085A for ; Fri, 19 Jul 2019 05:53:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=neuling.org header.i=@neuling.org header.b="Znn2KVe6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2665D2085A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=neuling.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45qgCw4PFmzDqv1 for ; Fri, 19 Jul 2019 15:53:32 +1000 (AEST) Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 45qf845s44zDqMB for ; Fri, 19 Jul 2019 15:05:08 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=neuling.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=neuling.org header.i=@neuling.org header.b="Znn2KVe6"; dkim-atps=neutral Received: from neuling.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 45qf836QDkz9s00; Fri, 19 Jul 2019 15:05:07 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=neuling.org; s=201811; t=1563512707; bh=M+utsh9UbAsD43z7wK4lS+57JCI6TToPn3sL83++q5k=; h=From:To:Cc:Subject:Date:From; b=Znn2KVe6t3HWwaFhpNM4s2SWpg5QKgs+t8FoMeIxdT4O2yZbEOLJDnAAhlNyeokfK 2P33GwGq+yc9BVgmQ68xJyofRQ9RdrIxPmljqTWykaSHuXpMghP51bKax5o3PBRdqJ zEVYVgZOMhpxL7tPRjHBheLFSjnyJhmF185w+tNUU5MImOIKPcIRHSDsBItKeCHKZb nJ8qi4xvPvJpQ9oVVJjyU+Cr9sC+UiuJ8maXO/ZSCcBqC/WclCbRKwcmr0m5WLPjYX NYcI3/qFCXeUwPnT7+n2VSugxziLcioBOvVbuk0ree3ykkSCOVS+VxfrifsXu7aoGo Tkc4FGe9f/PhQ== Received: by neuling.org (Postfix, from userid 1000) id C62EA2A1025; Fri, 19 Jul 2019 15:05:07 +1000 (AEST) From: Michael Neuling To: mpe@ellerman.id.au Subject: [PATCH] powerpc/tm: Fix oops on sigreturn on systems without TM Date: Fri, 19 Jul 2019 15:05:02 +1000 Message-Id: <20190719050502.405-1-mikey@neuling.org> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mikey@neuling.org, Praveen Pandey , gromero@br.ibm.com, linuxppc-dev@lists.ozlabs.org, Breno Leitao , Haren Myneni Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On systems like P9 powernv where we have no TM (or P8 booted with ppc_tm=off), userspace can construct a signal context which still has the MSR TS bits set. The kernel tries to restore this context which results in the following crash: [ 74.980557] Unexpected TM Bad Thing exception at c0000000000022fc (msr 0x8000000102a03031) tm_scratch=800000020280f033 [ 74.980741] Oops: Unrecoverable exception, sig: 6 [#1] [ 74.980820] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries [ 74.980917] Modules linked in: [ 74.980980] CPU: 0 PID: 1636 Comm: sigfuz Not tainted 5.2.0-11043-g0a8ad0ffa4 #69 [ 74.981096] NIP: c0000000000022fc LR: 00007fffb2d67e48 CTR: 0000000000000000 [ 74.981212] REGS: c00000003fffbd70 TRAP: 0700 Not tainted (5.2.0-11045-g7142b497d8) [ 74.981325] MSR: 8000000102a03031 CR: 42004242 XER: 00000000 [ 74.981463] CFAR: c0000000000022e0 IRQMASK: 0 [ 74.981463] GPR00: 0000000000000072 00007fffb2b6e560 00007fffb2d87f00 0000000000000669 [ 74.981463] GPR04: 00007fffb2b6e728 0000000000000000 0000000000000000 00007fffb2b6f2a8 [ 74.981463] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 [ 74.981463] GPR12: 0000000000000000 00007fffb2b76900 0000000000000000 0000000000000000 [ 74.981463] GPR16: 00007fffb2370000 00007fffb2d84390 00007fffea3a15ac 000001000a250420 [ 74.981463] GPR20: 00007fffb2b6f260 0000000010001770 0000000000000000 0000000000000000 [ 74.981463] GPR24: 00007fffb2d843a0 00007fffea3a14a0 0000000000010000 0000000000800000 [ 74.981463] GPR28: 00007fffea3a14d8 00000000003d0f00 0000000000000000 00007fffb2b6e728 [ 74.982420] NIP [c0000000000022fc] rfi_flush_fallback+0x7c/0x80 [ 74.982517] LR [00007fffb2d67e48] 0x7fffb2d67e48 [ 74.982593] Call Trace: [ 74.982632] Instruction dump: [ 74.982691] e96a0220 e96a02a8 e96a0330 e96a03b8 394a0400 4200ffdc 7d2903a6 e92d0c00 [ 74.982809] e94d0c08 e96d0c10 e82d0c18 7db242a6 <4c000024> 7db243a6 7db142a6 f82d0c18 The problem is the signal code assumes TM is enabled when CONFIG_PPC_TRANSACTIONAL_MEM is on. This may not be the case as with P9 powernv or if `ppc_tm=off` is used on P8. This means any local user can crash the system. Fix the problem by returning a bad stack frame to the user if they try to set the MSR TS bits with sigreturn() on systems where TM is not supported. Found with sigfuz kernel selftest on P9. This fixes CVE-2019-13648. Fixes: 2b0a576d15 ("powerpc: Add new transactional memory state to the signal context") Cc: stable@vger.kernel.org # v3.9 Reported-by: Praveen Pandey Signed-off-by: Michael Neuling --- arch/powerpc/kernel/signal_32.c | 3 +++ arch/powerpc/kernel/signal_64.c | 5 +++++ 2 files changed, 8 insertions(+) diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c index f50b708d6d..98600b276f 100644 --- a/arch/powerpc/kernel/signal_32.c +++ b/arch/powerpc/kernel/signal_32.c @@ -1198,6 +1198,9 @@ SYSCALL_DEFINE0(rt_sigreturn) goto bad; if (MSR_TM_ACTIVE(msr_hi<<32)) { + /* Trying to start TM on non TM system */ + if (!cpu_has_feature(CPU_FTR_TM)) + goto bad; /* We only recheckpoint on return if we're * transaction. */ diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index 2f80e270c7..117515564e 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -771,6 +771,11 @@ SYSCALL_DEFINE0(rt_sigreturn) if (MSR_TM_ACTIVE(msr)) { /* We recheckpoint on return. */ struct ucontext __user *uc_transact; + + /* Trying to start TM on non TM system */ + if (!cpu_has_feature(CPU_FTR_TM)) + goto badframe; + if (__get_user(uc_transact, &uc->uc_link)) goto badframe; if (restore_tm_sigcontexts(current, &uc->uc_mcontext, -- 2.21.0