From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] mm/kasan: Don't vfree() nonexistent vm_area. From: David Hildenbrand To: Andrey Ryabinin , Andrew Morton Cc: Paul Menzel , Alexander Potapenko , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org References: <12c9e499-9c11-d248-6a3f-14ec8c4e07f1@molgen.mpg.de> <20180201163349.8700-1-aryabinin@virtuozzo.com> <784dfdf6-8fc3-be08-833b-a9097c3d1b96@redhat.com> Message-ID: <6982f59e-c836-1064-c05c-a926446b6f48@redhat.com> Date: Fri, 18 May 2018 18:01:02 +0200 MIME-Version: 1.0 In-Reply-To: <784dfdf6-8fc3-be08-833b-a9097c3d1b96@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: On 18.05.2018 17:57, David Hildenbrand wrote: > On 01.02.2018 17:33, Andrey Ryabinin wrote: >> KASAN uses different routines to map shadow for hot added memory and memory >> obtained in boot process. Attempt to offline memory onlined by normal boot >> process leads to this: >> >> Trying to vfree() nonexistent vm area (000000005d3b34b9) >> WARNING: CPU: 2 PID: 13215 at mm/vmalloc.c:1525 __vunmap+0x147/0x190 >> >> Call Trace: >> kasan_mem_notifier+0xad/0xb9 >> notifier_call_chain+0x166/0x260 >> __blocking_notifier_call_chain+0xdb/0x140 >> __offline_pages+0x96a/0xb10 >> memory_subsys_offline+0x76/0xc0 >> device_offline+0xb8/0x120 >> store_mem_state+0xfa/0x120 >> kernfs_fop_write+0x1d5/0x320 >> __vfs_write+0xd4/0x530 >> vfs_write+0x105/0x340 >> SyS_write+0xb0/0x140 >> >> Obviously we can't call vfree() to free memory that wasn't allocated via >> vmalloc(). Use find_vm_area() to see if we can call vfree(). >> >> Unfortunately it's a bit tricky to properly unmap and free shadow allocated >> during boot, so we'll have to keep it. If memory will come online again >> that shadow will be reused. >> > > While debugging kasan memory hotplug problems I am having, stumbled over > this patch. > > Couldn't we handle that via VM_KASAN like in kasan_module_alloc/free > instead? > Just realized that this will most probably not work. So please ignore my comment for now :) -- Thanks, David / dhildenb