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=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 858ECC4332D for ; Fri, 19 Mar 2021 05:44:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4201664F7A for ; Fri, 19 Mar 2021 05:44:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233897AbhCSFna (ORCPT ); Fri, 19 Mar 2021 01:43:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:47784 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230337AbhCSFm6 (ORCPT ); Fri, 19 Mar 2021 01:42:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A9AA164DCC; Fri, 19 Mar 2021 05:42:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616132578; bh=eUscbhRfkwQ3BScJNzBWpmoaoPTaH2/CrSy667cXmSo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tgqo1fiAkRoibCXJIE+kRXm9B7zHFlQ3ZjkYujbyCmY/dDEE0Jy62q6f9XXHt4iIO /p23bnuLpXB29+L+t3a70FztoobrfKvnmT0Bs1saabnWd5AfaTGDAlt8Xo70I0G34/ d0ZZJZRz+N53xxtXUF/HDClQdzyjJVEmAxDJHb5NYlSFrlPOW0yjOFNNxSi4KpHyz+ ibM33xZZQNJIerRMOx6TVMCPKGq2OwKzZv63v542d1a1I3cOGUP2Uf2gx+phrVEzcv lkgm2gw/7bksxlh3HS+1ofIrAfbfBnso20XPGttISS7t0j3moc6w016C1YOxuSHJZg LuaAb2k8uy4Rw== Date: Fri, 19 Mar 2021 07:42:31 +0200 From: Jarkko Sakkinen To: Kai Huang Cc: x86@kernel.org, linux-sgx@vger.kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, dave.hansen@intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/sgx: Avoid returning NULL in __sgx_alloc_epc_page() Message-ID: References: <20210319040602.178558-1-kai.huang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210319040602.178558-1-kai.huang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 19, 2021 at 05:06:02PM +1300, Kai Huang wrote: > Below kernel bug happened when running simple SGX application when EPC > is under pressure. The root cause is with commit 5b8719504e3a > ("x86/sgx: Add a basic NUMA allocation scheme to sgx_alloc_epc_page()"), > __sgx_alloc_epc_page() returns NULL when there's no free EPC page can be > allocated, while old behavior was it always returned ERR_PTR(-ENOMEM) in > such case. > > Fix by directly returning the page if __sgx_alloc_epc_page_from_node() > allocates a valid page in fallback to non-local allocation, and always > returning ERR_PTR(-ENOMEM) if no EPC page can be allocated. > > [ 253.474764] BUG: kernel NULL pointer dereference, address: 0000000000000008 > [ 253.500101] #PF: supervisor write access in kernel mode > [ 253.525462] #PF: error_code(0x0002) - not-present page > ... > [ 254.102041] Call Trace: > [ 254.126699] sgx_ioc_enclave_add_pages+0x241/0x770 > [ 254.151305] sgx_ioctl+0x194/0x4b0 > [ 254.174976] ? handle_mm_fault+0xd0/0x260 > [ 254.198470] ? do_user_addr_fault+0x1ef/0x570 > [ 254.221827] __x64_sys_ioctl+0x91/0xc0 > [ 254.244546] do_syscall_64+0x38/0x90 > [ 254.266728] entry_SYSCALL_64_after_hwframe+0x44/0xae > [ 254.289232] RIP: 0033:0x7fdc4cf4031b > ... > [ 254.711480] CR2: 0000000000000008 > [ 254.735494] ---[ end trace 970dce6d4cdf7f64 ]--- > [ 254.759915] RIP: 0010:sgx_alloc_epc_page+0x46/0x152 > ... > > Fixes: 5b8719504e3a("x86/sgx: Add a basic NUMA allocation scheme to sgx_alloc_epc_page()") > Signed-off-by: Kai Huang Reviewed-by: Jarkko Sakkinen > --- > arch/x86/kernel/cpu/sgx/main.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index fe26e7e91c25..7105e34da530 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -508,10 +508,10 @@ struct sgx_epc_page *__sgx_alloc_epc_page(void) > > page = __sgx_alloc_epc_page_from_node(nid); > if (page) > - break; > + return page; > } > > - return page; > + return ERR_PTR(-ENOMEM); > } > > /** > -- > 2.30.2 > > /Jarkko