From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755345AbeD3XEi (ORCPT ); Mon, 30 Apr 2018 19:04:38 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42314 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751384AbeD3XEh (ORCPT ); Mon, 30 Apr 2018 19:04:37 -0400 Date: Mon, 30 Apr 2018 16:04:36 -0700 From: Andrew Morton To: Chintan Pandya Cc: vbabka@suse.cz, labbott@redhat.com, catalin.marinas@arm.com, hannes@cmpxchg.org, f.fainelli@gmail.com, xieyisheng1@huawei.com, ard.biesheuvel@linaro.org, richard.weiyang@gmail.com, byungchul.park@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, khandual@linux.vnet.ibm.com, mhocko@kernel.org Subject: Re: [PATCH v2 2/2] mm: vmalloc: Pass proper vm_start into debugobjects Message-Id: <20180430160436.45f92ec5b3c78c84e4425ec4@linux-foundation.org> In-Reply-To: <1523961828-9485-3-git-send-email-cpandya@codeaurora.org> References: <1523961828-9485-1-git-send-email-cpandya@codeaurora.org> <1523961828-9485-3-git-send-email-cpandya@codeaurora.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 17 Apr 2018 16:13:48 +0530 Chintan Pandya wrote: > Client can call vunmap with some intermediate 'addr' > which may not be the start of the VM area. Entire > unmap code works with vm->vm_start which is proper > but debug object API is called with 'addr'. This > could be a problem within debug objects. As far as I can tell this is indeed the case, but it's a pretty weird thing for us to do. I wonder if there is any code in the kernel which is passing such an offset address into vunmap(). If so, perhaps we should check for it and do a WARN_ONCE so it gets fixed. > Pass proper start address into debug object API. > > ... > > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1124,15 +1124,15 @@ void vm_unmap_ram(const void *mem, unsigned int count) > BUG_ON(addr > VMALLOC_END); > BUG_ON(!PAGE_ALIGNED(addr)); > > - debug_check_no_locks_freed(mem, size); > - > if (likely(count <= VMAP_MAX_ALLOC)) { > + debug_check_no_locks_freed(mem, size); But this still has the problem you described, no? Shouldn't we be doing yet another find_vmap_area()? > vb_free(mem, size); > return; > } > > va = find_vmap_area(addr); > BUG_ON(!va); > + debug_check_no_locks_freed(va->va_start, (va->va_end - va->va_start)); > free_unmap_vmap_area(va); > } > EXPORT_SYMBOL(vm_unmap_ram); > @@ -1507,8 +1507,8 @@ static void __vunmap(const void *addr, int deallocate_pages) > return; > } > > - debug_check_no_locks_freed(addr, get_vm_area_size(area)); > - debug_check_no_obj_freed(addr, get_vm_area_size(area)); > + debug_check_no_locks_freed(area->addr, get_vm_area_size(area)); > + debug_check_no_obj_freed(area->addr, get_vm_area_size(area)); > Offtopic: it's a bit sad that __vunmap() does the find_vmap_area() then calls remove_vm_area() which runs find_vmap_area() yet again...