From patchwork Tue Oct 10 11:47:50 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Ellerman X-Patchwork-Id: 1845840 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=LPvG7yFk; dkim-atps=neutral Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=2404:9400:2:0:216:3eff:fee1:b9f1; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=patchwork.ozlabs.org) Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2404:9400:2:0:216:3eff:fee1:b9f1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1) server-digest SHA384) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4S4Z0m1rnBz23jb for ; Tue, 10 Oct 2023 22:48:22 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=LPvG7yFk; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4S4Z0k455Wz2yMJ for ; Tue, 10 Oct 2023 22:48:22 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=LPvG7yFk; dkim-atps=neutral Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) (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 4S4Z0N2lzJz30P0 for ; Tue, 10 Oct 2023 22:48:04 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1696938483; bh=3RrloAUYJLow9MEEKipUVgFNIUhEqEFkUDg4lS5JExc=; h=From:To:Cc:Subject:Date:From; b=LPvG7yFk1fKyqCYtrapmvIJH4id2RpfVMEsSnkUExJJgunZOG+vQkcjE7qrH/z7BN q7usNqYKA1hpDDQesgqmP1cWZm5XI899V3JyfEeMI7AkT5ZBGZmst4SVOPZgNP2z/p opeddfQ/lkBci3viSHAPjMz8qNBgG2P5sQToAOG7hyiyXl6LA4bgW6xwPzcZq+96X0 KP8El130xk2EteaapoKvXIC6WuTbs1fvsShgUcnv0WOmxFBhKzD6TZXnLK6sslrthk KoM/litFRh4XlE9lg5Xx4cSfGNzbva+c7tEz9T/GYS5yyKUEf0fTgBhRuOK49BjxO3 XVlduBfU3LIiw== Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4S4Z0L6ycZz4x3H; Tue, 10 Oct 2023 22:48:02 +1100 (AEDT) From: Michael Ellerman To: Subject: [PATCH] powerpc/47x: Fix 47x syscall return crash Date: Tue, 10 Oct 2023 22:47:50 +1100 Message-ID: <20231010114750.847794-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 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: eajames@linux.ibm.com Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Eddie reported that newer kernels were crashing during boot on his 476 FSP2 system: kernel tried to execute user page (b7ee2000) - exploit attempt? (uid: 0) BUG: Unable to handle kernel instruction fetch Faulting instruction address: 0xb7ee2000 Oops: Kernel access of bad area, sig: 11 [#1] BE PAGE_SIZE=4K FSP-2 Modules linked in: CPU: 0 PID: 61 Comm: mount Not tainted 6.1.55-d23900f.ppcnf-fsp2 #1 Hardware name: ibm,fsp2 476fpe 0x7ff520c0 FSP-2 NIP:  b7ee2000 LR: 8c008000 CTR: 00000000 REGS: bffebd83 TRAP: 0400   Not tainted (6.1.55-d23900f.ppcnf-fs p2) MSR:  00000030   CR: 00001000  XER: 20000000 GPR00: c00110ac bffebe63 bffebe7e bffebe88 8c008000 00001000 00000d12 b7ee2000 GPR08: 00000033 00000000 00000000 c139df10 48224824 1016c314 10160000 00000000 GPR16: 10160000 10160000 00000008 00000000 10160000 00000000 10160000 1017f5b0 GPR24: 1017fa50 1017f4f0 1017fa50 1017f740 1017f630 00000000 00000000 1017f4f0 NIP [b7ee2000] 0xb7ee2000 LR [8c008000] 0x8c008000 Call Trace: Instruction dump: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX ---[ end trace 0000000000000000 ]--- The problem is in ret_from_syscall where the check for icache_44x_need_flush is done. When the flush is needed the code jumps out-of-line to do the flush, and then intends to jump back to continue the syscall return. However the branch back to label 1b doesn't return to the correct location, instead branching back just prior to the return to userspace, causing bogus register values to be used by the rfi. The breakage was introduced by commit 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") which inadvertently removed the "1" label and reused it elsewhere. Fix it by adding named local labels in the correct locations. Note that the return label needs to be outside the ifdef so that CONFIG_PPC_47x=n compiles. Fixes: 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") Cc: stable@vger.kernel.org # v5.12+ Reported-by: Eddie James Link: https://lore.kernel.org/linuxppc-dev/fdaadc46-7476-9237-e104-1d2168526e72@linux.ibm.com/ Signed-off-by: Michael Ellerman Tested-by: Eddie James Reviewed-by: Christophe Leroy --- arch/powerpc/kernel/entry_32.S | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 9692acb0361f..7eda33a24bb4 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -137,8 +137,9 @@ ret_from_syscall: lis r4,icache_44x_need_flush@ha lwz r5,icache_44x_need_flush@l(r4) cmplwi cr0,r5,0 - bne- 2f + bne- .L44x_icache_flush #endif /* CONFIG_PPC_47x */ +.L44x_icache_flush_return: kuep_unlock lwz r4,_LINK(r1) lwz r5,_CCR(r1) @@ -172,10 +173,11 @@ syscall_exit_finish: b 1b #ifdef CONFIG_44x -2: li r7,0 +.L44x_icache_flush: + li r7,0 iccci r0,r0 stw r7,icache_44x_need_flush@l(r4) - b 1b + b .L44x_icache_flush_return #endif /* CONFIG_44x */ .globl ret_from_fork