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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD93CC433EF for ; Fri, 19 Nov 2021 15:13:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9267B611CC for ; Fri, 19 Nov 2021 15:13:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234343AbhKSPQD (ORCPT ); Fri, 19 Nov 2021 10:16:03 -0500 Received: from mailgw01.mediatek.com ([60.244.123.138]:44100 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S229879AbhKSPQC (ORCPT ); Fri, 19 Nov 2021 10:16:02 -0500 X-UUID: 0aeac716630e475c87c099b9aa70375d-20211119 X-UUID: 0aeac716630e475c87c099b9aa70375d-20211119 Received: from mtkexhb01.mediatek.inc [(172.21.101.102)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 1689223143; Fri, 19 Nov 2021 23:12:57 +0800 Received: from mtkcas10.mediatek.inc (172.21.101.39) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.15; Fri, 19 Nov 2021 23:12:56 +0800 Received: from mtksdccf07 (172.21.84.99) by mtkcas10.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Fri, 19 Nov 2021 23:12:55 +0800 Message-ID: Subject: Re: [PATCH] kmemleak: fix kmemleak false positive report with HW tag-based kasan enable From: Kuan-Ying Lee To: Andrey Konovalov CC: Catalin Marinas , Andrew Morton , Matthias Brugger , Chinwen Chang =?UTF-8?Q?=28=E5=BC=B5=E9=8C=A6=E6=96=87=29?= , Nicholas Tang =?UTF-8?Q?=28=E9=84=AD=E7=A7=A6=E8=BC=9D=29?= , James Hsu =?UTF-8?Q?=28=E5=BE=90=E6=85=B6=E8=96=B0=29?= , Yee Lee =?UTF-8?Q?=28=E6=9D=8E=E5=BB=BA=E8=AA=BC=29?= , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mediatek@lists.infradead.org" , kasan-dev , Date: Fri, 19 Nov 2021 23:12:55 +0800 In-Reply-To: References: <20211118054426.4123-1-Kuan-Ying.Lee@mediatek.com> <754511d9a0368065768cc3ad8037184d62c3fbd1.camel@mediatek.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2021-11-19 at 22:15 +0800, Andrey Konovalov wrote: > On Thu, Nov 18, 2021 at 10:20 AM Kuan-Ying Lee > wrote: > > > > +Cc kasan group > > > > On Thu, 2021-11-18 at 13:44 +0800, Kuan-Ying Lee wrote: > > > With HW tag-based kasan enable, We will get the warning > > > when we free object whose address starts with 0xFF. > > > > > > It is because kmemleak rbtree stores tagged object and > > > this freeing object's tag does not match with rbtree object. > > > > > > In the example below, kmemleak rbtree stores the tagged object in > > > the kmalloc(), and kfree() gets the pointer with 0xFF tag. > > > > > > Call sequence: > > > ptr = kmalloc(size, GFP_KERNEL); > > > page = virt_to_page(ptr); > > > kfree(page_address(page)); > > > ptr = kmalloc(size, GFP_KERNEL); > > How is this call sequence valid? page_address returns the address of > the start of the page, while kmalloced object could have been located > in the middle of it. Thanks for pointing out. I miss the offset. It should be listed as below. ptr = kmalloc(size, GFP_KERNEL); page = virt_to_page(ptr); offset = offset_in_page(ptr); kfree(page_address(page) + offset); ptr = kmalloc(size, GFP_KERNEL); > > > > > > > Call sequence like that may cause the warning as following: > > > 1) Freeing unknown object: > > > In kfree(), we will get free unknown object warning in > > > kmemleak_free(). > > > Because object(0xFx) in kmemleak rbtree and pointer(0xFF) in > > > kfree() > > > have > > > different tag. > > > > > > 2) Overlap existing: > > > When we allocate that object with the same hw-tag again, we will > > > find the overlap in the kmemleak rbtree and kmemleak thread will > > > be killed. > > > > > > [ 116.685312] kmemleak: Freeing unknown object at > > > 0xffff000003f88000 > > > [ 116.686422] CPU: 5 PID: 177 Comm: cat Not tainted 5.16.0-rc1- > > > dirty > > > #21 > > > [ 116.687067] Hardware name: linux,dummy-virt (DT) > > > [ 116.687496] Call trace: > > > [ 116.687792] dump_backtrace+0x0/0x1ac > > > [ 116.688255] show_stack+0x1c/0x30 > > > [ 116.688663] dump_stack_lvl+0x68/0x84 > > > [ 116.689096] dump_stack+0x1c/0x38 > > > [ 116.689499] kmemleak_free+0x6c/0x70 > > > [ 116.689919] slab_free_freelist_hook+0x104/0x200 > > > [ 116.690420] kmem_cache_free+0xa8/0x3d4 > > > [ 116.690845] test_version_show+0x270/0x3a0 > > > [ 116.691344] module_attr_show+0x28/0x40 > > > [ 116.691789] sysfs_kf_seq_show+0xb0/0x130 > > > [ 116.692245] kernfs_seq_show+0x30/0x40 > > > [ 116.692678] seq_read_iter+0x1bc/0x4b0 > > > [ 116.692678] seq_read_iter+0x1bc/0x4b0 > > > [ 116.693114] kernfs_fop_read_iter+0x144/0x1c0 > > > [ 116.693586] generic_file_splice_read+0xd0/0x184 > > > [ 116.694078] do_splice_to+0x90/0xe0 > > > [ 116.694498] splice_direct_to_actor+0xb8/0x250 > > > [ 116.694975] do_splice_direct+0x88/0xd4 > > > [ 116.695409] do_sendfile+0x2b0/0x344 > > > [ 116.695829] __arm64_sys_sendfile64+0x164/0x16c > > > [ 116.696306] invoke_syscall+0x48/0x114 > > > [ 116.696735] el0_svc_common.constprop.0+0x44/0xec > > > [ 116.697263] do_el0_svc+0x74/0x90 > > > [ 116.697665] el0_svc+0x20/0x80 > > > [ 116.698261] el0t_64_sync_handler+0x1a8/0x1b0 > > > [ 116.698695] el0t_64_sync+0x1ac/0x1b0 > > > ... > > > [ 117.520301] kmemleak: Cannot insert 0xf2ff000003f88000 into > > > the > > > object search tree (overlaps existing) > > > [ 117.521118] CPU: 5 PID: 178 Comm: cat Not tainted 5.16.0-rc1- > > > dirty > > > #21 > > > [ 117.521827] Hardware name: linux,dummy-virt (DT) > > > [ 117.522287] Call trace: > > > [ 117.522586] dump_backtrace+0x0/0x1ac > > > [ 117.523053] show_stack+0x1c/0x30 > > > [ 117.523578] dump_stack_lvl+0x68/0x84 > > > [ 117.524039] dump_stack+0x1c/0x38 > > > [ 117.524472] create_object.isra.0+0x2d8/0x2fc > > > [ 117.524975] kmemleak_alloc+0x34/0x40 > > > [ 117.525416] kmem_cache_alloc+0x23c/0x2f0 > > > [ 117.525914] test_version_show+0x1fc/0x3a0 > > > [ 117.526379] module_attr_show+0x28/0x40 > > > [ 117.526827] sysfs_kf_seq_show+0xb0/0x130 > > > [ 117.527363] kernfs_seq_show+0x30/0x40 > > > [ 117.527848] seq_read_iter+0x1bc/0x4b0 > > > [ 117.528320] kernfs_fop_read_iter+0x144/0x1c0 > > > [ 117.528809] generic_file_splice_read+0xd0/0x184 > > > [ 117.529316] do_splice_to+0x90/0xe0 > > > [ 117.529734] splice_direct_to_actor+0xb8/0x250 > > > [ 117.530227] do_splice_direct+0x88/0xd4 > > > [ 117.530686] do_sendfile+0x2b0/0x344 > > > [ 117.531154] __arm64_sys_sendfile64+0x164/0x16c > > > [ 117.531673] invoke_syscall+0x48/0x114 > > > [ 117.532111] el0_svc_common.constprop.0+0x44/0xec > > > [ 117.532621] do_el0_svc+0x74/0x90 > > > [ 117.533048] el0_svc+0x20/0x80 > > > [ 117.533461] el0t_64_sync_handler+0x1a8/0x1b0 > > > [ 117.533950] el0t_64_sync+0x1ac/0x1b0 > > > [ 117.534625] kmemleak: Kernel memory leak detector disabled > > > [ 117.535201] kmemleak: Object 0xf2ff000003f88000 (size 128): > > > [ 117.535761] kmemleak: comm "cat", pid 177, jiffies > > > 4294921177 > > > [ 117.536339] kmemleak: min_count = 1 > > > [ 117.536718] kmemleak: count = 0 > > > [ 117.537068] kmemleak: flags = 0x1 > > > [ 117.537429] kmemleak: checksum = 0 > > > [ 117.537806] kmemleak: backtrace: > > > [ 117.538211] kmem_cache_alloc+0x23c/0x2f0 > > > [ 117.538924] test_version_show+0x1fc/0x3a0 > > > [ 117.539393] module_attr_show+0x28/0x40 > > > [ 117.539844] sysfs_kf_seq_show+0xb0/0x130 > > > [ 117.540304] kernfs_seq_show+0x30/0x40 > > > [ 117.540750] seq_read_iter+0x1bc/0x4b0 > > > [ 117.541206] kernfs_fop_read_iter+0x144/0x1c0 > > > [ 117.541687] generic_file_splice_read+0xd0/0x184 > > > [ 117.542182] do_splice_to+0x90/0xe0 > > > [ 117.542611] splice_direct_to_actor+0xb8/0x250 > > > [ 117.543097] do_splice_direct+0x88/0xd4 > > > [ 117.543544] do_sendfile+0x2b0/0x344 > > > [ 117.543983] __arm64_sys_sendfile64+0x164/0x16c > > > [ 117.544471] invoke_syscall+0x48/0x114 > > > [ 117.544917] el0_svc_common.constprop.0+0x44/0xec > > > [ 117.545416] do_el0_svc+0x74/0x90 > > > [ 117.554100] kmemleak: Automatic memory scanning thread ended > > > > > > Signed-off-by: Kuan-Ying Lee > > > --- > > > mm/kmemleak.c | 17 ++++++++++++----- > > > 1 file changed, 12 insertions(+), 5 deletions(-) > > > > > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > > > index b57383c17cf6..fa12e2e08cdc 100644 > > > --- a/mm/kmemleak.c > > > +++ b/mm/kmemleak.c > > > @@ -381,15 +381,20 @@ static void dump_object_info(struct > > > kmemleak_object *object) > > > static struct kmemleak_object *lookup_object(unsigned long ptr, > > > int > > > alias) > > > { > > > struct rb_node *rb = object_tree_root.rb_node; > > > + unsigned long untagged_ptr = (unsigned > > > long)kasan_reset_tag((void *)ptr); > > > > > > while (rb) { > > > struct kmemleak_object *object = > > > rb_entry(rb, struct kmemleak_object, > > > rb_node); > > > - if (ptr < object->pointer) > > > + unsigned long untagged_objp; > > > + > > > + untagged_objp = (unsigned > > > long)kasan_reset_tag((void > > > *)object->pointer); > > > + > > > + if (untagged_ptr < untagged_objp) > > > rb = object->rb_node.rb_left; > > > - else if (object->pointer + object->size <= ptr) > > > + else if (untagged_objp + object->size <= > > > untagged_ptr) > > > rb = object->rb_node.rb_right; > > > - else if (object->pointer == ptr || alias) > > > + else if (untagged_objp == untagged_ptr || alias) > > > return object; > > > else { > > > kmemleak_warn("Found object by alias at > > > 0x%08lx\n", > > > @@ -576,6 +581,7 @@ static struct kmemleak_object > > > *create_object(unsigned long ptr, size_t size, > > > struct kmemleak_object *object, *parent; > > > struct rb_node **link, *rb_parent; > > > unsigned long untagged_ptr; > > > + unsigned long untagged_objp; > > > > > > object = mem_pool_alloc(gfp); > > > if (!object) { > > > @@ -629,9 +635,10 @@ static struct kmemleak_object > > > *create_object(unsigned long ptr, size_t size, > > > while (*link) { > > > rb_parent = *link; > > > parent = rb_entry(rb_parent, struct > > > kmemleak_object, > > > rb_node); > > > - if (ptr + size <= parent->pointer) > > > + untagged_objp = (unsigned > > > long)kasan_reset_tag((void > > > *)parent->pointer); > > > + if (untagged_ptr + size <= untagged_objp) > > > link = &parent->rb_node.rb_left; > > > - else if (parent->pointer + parent->size <= ptr) > > > + else if (untagged_objp + parent->size <= > > > untagged_ptr) > > > link = &parent->rb_node.rb_right; > > > else { > > > kmemleak_stop("Cannot insert 0x%lx into the > > > object search tree (overlaps existing)\n", > > > -- > > > 2.18.0 > > > > > > > -- > > You received this message because you are subscribed to the Google > > Groups "kasan-dev" group. > > To unsubscribe from this group and stop receiving emails from it, > > send an email to kasan-dev+unsubscribe@googlegroups.com. > > To view this discussion on the web visit > > https://urldefense.com/v3/__https://groups.google.com/d/msgid/kasan-dev/754511d9a0368065768cc3ad8037184d62c3fbd1.camel*40mediatek.com__;JQ!!CTRNKA9wMg0ARbw!y7gGU0PsiMId4XiGTZzBUUL_WtWQ24nnTQtGbFrZ46wqfwk8ZeYCVP2pYmNFHrAUGOKr1g$ > > .