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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6BABC67861 for ; Tue, 9 Apr 2024 14:29:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 67A326B0088; Tue, 9 Apr 2024 10:29:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 62A106B0089; Tue, 9 Apr 2024 10:29:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4F31E6B008A; Tue, 9 Apr 2024 10:29:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 306B06B0088 for ; Tue, 9 Apr 2024 10:29:00 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id D95CEA0BBF for ; 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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1712672938; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=O162Au2HGGfJnds2vJPLMT8AqodUGMKqcVOul01Xz+w=; b=kBJuKUoy8Ii48SvdslzttZRn47Z+bMVZSjw4woXpblVaH1S1GBAkmiiC99tuqkoYLBlvQP bP1TribT0zmkrWxwOKt/o86wyrQ6gfScpESgk8nWmYmGB1zOSw8CdUT+TJXRxekBRhVt4h RvXFRqIJ4sGasmInOv/Afov4KZ8Gfhk= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 4F752CE11BD; Tue, 9 Apr 2024 14:28:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42475C433F1; Tue, 9 Apr 2024 14:28:51 +0000 (UTC) Date: Tue, 9 Apr 2024 15:28:44 +0100 From: Catalin Marinas To: Kefeng Wang Cc: Andrew Morton , Russell King , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH 1/2] arm64: mm: drop VM_FAULT_BADMAP/VM_FAULT_BADACCESS Message-ID: References: <20240407081211.2292362-1-wangkefeng.wang@huawei.com> <20240407081211.2292362-2-wangkefeng.wang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240407081211.2292362-2-wangkefeng.wang@huawei.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C19968000B X-Stat-Signature: 4n59fhyxyhhbgdmd3o6744bt7uadimya X-Rspam-User: X-HE-Tag: 1712672937-276937 X-HE-Meta: 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 UEi+zIcP Me5nl7qckKLUseMy1B3LT7QXv1mbpkPLmlZCOLVgKamvwfMM81/wWdCFtzlA5S98sstoG7JxGQSsP42QcgORXPPAu5g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Kefeng, On Sun, Apr 07, 2024 at 04:12:10PM +0800, Kefeng Wang wrote: > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 405f9aa831bd..61a2acae0dca 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -500,9 +500,6 @@ static bool is_write_abort(unsigned long esr) > return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM); > } > > -#define VM_FAULT_BADMAP ((__force vm_fault_t)0x010000) > -#define VM_FAULT_BADACCESS ((__force vm_fault_t)0x020000) > - > static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > struct pt_regs *regs) > { > @@ -513,6 +510,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > unsigned int mm_flags = FAULT_FLAG_DEFAULT; > unsigned long addr = untagged_addr(far); > struct vm_area_struct *vma; > + int si_code; I think we should initialise this to 0. Currently all paths seem to set si_code to something meaningful but I'm not sure the last 'else' close in this patch is guaranteed to always cover exactly those earlier code paths updating si_code. I'm not talking about the 'goto bad_area' paths since they set 'fault' to 0 but the fall through after the second (under the mm lock) handle_mm_fault(). > if (kprobe_page_fault(regs, esr)) > return 0; > @@ -572,9 +570,10 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > > if (!(vma->vm_flags & vm_flags)) { > vma_end_read(vma); > - fault = VM_FAULT_BADACCESS; > + fault = 0; > + si_code = SEGV_ACCERR; > count_vm_vma_lock_event(VMA_LOCK_SUCCESS); > - goto done; > + goto bad_area; > } > fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs); > if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) > @@ -599,15 +598,18 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > retry: > vma = lock_mm_and_find_vma(mm, addr, regs); > if (unlikely(!vma)) { > - fault = VM_FAULT_BADMAP; > - goto done; > + fault = 0; > + si_code = SEGV_MAPERR; > + goto bad_area; > } > > - if (!(vma->vm_flags & vm_flags)) > - fault = VM_FAULT_BADACCESS; > - else > - fault = handle_mm_fault(vma, addr, mm_flags, regs); > + if (!(vma->vm_flags & vm_flags)) { > + fault = 0; > + si_code = SEGV_ACCERR; > + goto bad_area; > + } What's releasing the mm lock here? Prior to this change, it is falling through to mmap_read_unlock() below or handle_mm_fault() was releasing the lock (VM_FAULT_RETRY, VM_FAULT_COMPLETED). > > + fault = handle_mm_fault(vma, addr, mm_flags, regs); > /* Quick path to respond to signals */ > if (fault_signal_pending(fault, regs)) { > if (!user_mode(regs)) > @@ -626,13 +628,11 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > mmap_read_unlock(mm); > > done: > - /* > - * Handle the "normal" (no error) case first. > - */ > - if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | > - VM_FAULT_BADACCESS)))) > + /* Handle the "normal" (no error) case first. */ > + if (likely(!(fault & VM_FAULT_ERROR))) > return 0; > > +bad_area: > /* > * If we are in kernel mode at this point, we have no context to > * handle this fault with. > @@ -667,13 +667,8 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > > arm64_force_sig_mceerr(BUS_MCEERR_AR, far, lsb, inf->name); > } else { > - /* > - * Something tried to access memory that isn't in our memory > - * map. > - */ > - arm64_force_sig_fault(SIGSEGV, > - fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR, > - far, inf->name); > + /* Something tried to access memory that out of memory map */ > + arm64_force_sig_fault(SIGSEGV, si_code, far, inf->name); > } We can get to the 'else' close after the second handle_mm_fault(). Do we guarantee that 'fault == 0' in this last block? If not, maybe a warning and some safe initialisation for 'si_code' to avoid leaking stack data. -- Catalin