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(Postfix, from userid 63042) id 7094E6B00A7; Fri, 19 Nov 2021 09:15:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0112.hostedemail.com [216.40.44.112]) by kanga.kvack.org (Postfix) with ESMTP id 61DC16B00A5 for ; Fri, 19 Nov 2021 09:15:47 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D11718B749 for ; Fri, 19 Nov 2021 14:15:36 +0000 (UTC) X-FDA: 78825877872.16.FA052F1 Received: from mail-io1-f45.google.com (mail-io1-f45.google.com [209.85.166.45]) by imf09.hostedemail.com (Postfix) with ESMTP id F3B893000117 for ; Fri, 19 Nov 2021 14:15:33 +0000 (UTC) Received: by mail-io1-f45.google.com with SMTP id y16so12904374ioc.8 for ; Fri, 19 Nov 2021 06:15:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0C7ROqxCmjaAbgYP83xHwXpa8YBysEBDejrqcdYrWb4=; b=TL+kYVRg53GtAuxVvS4grcqBr81SeAHrLkE46j7/yX6dDlQI/qtk1DFB5daEyM1/Mq 30ji1EDbv/Y2dMUvBB4X6x+pu4vn2zmkxFxMc72rniWX6t6ivy2bPebFt7zn6tYEIrC4 zeeFPmcV5cV1F8fKaHuAHvsohl39eY/MmH3qoxNOYVHxAjxWcr9jXu+kkXtUt4oD8+Lw B4lOSja/VlD9LQuF/H/BhgGitNDDzAovYXZ32Nu9HP7ADnszD85RAWh2SoeJOW8Tp6EA 4c9eJzAeBuX4A64vqpBe1Th/4ZQyIFiSdP49fHRfDU7pD0qW7gXdmApaF9Z+9BVLUe+3 pdjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0C7ROqxCmjaAbgYP83xHwXpa8YBysEBDejrqcdYrWb4=; b=a7Vp/ivKgz5i54JFUsSd42L7jge1NaWAJMG8p2NHMLzmd+gIv2AlwWlh6DzXbGCiyV CffIUp6gILdklE//8eajaObt+L1gRDpuzxC1WtNhLe3vdJHlSY/l0m6/MMnqFmNh9KBd EiohN4gUUbWzK3Rk+HpSKSojYpDq9o/8otAn38aalv0IHAVy27fgU2sv2B/tpnsUslRI XaJxRBkRD4XUFyGIG/VIc4qrDyw1i3vbZ1IszfuEhJLeDbuUN6lT7QVL931XNs8VbyGg 7OARzlbEq6Unvzi3kmNhvGHcAWc43djQmu9hQLmA6Mw7+IjuF1ucSv5jDEyVlnEBzlI0 eLQQ== X-Gm-Message-State: AOAM533xlSDZ+DINoQy0XpS/6w/hEx35KPdwA8vbfGAolph5Fb2f+RZ7 lfd2PpVTktxd/6JRyBwZ3rxBTvuifgERbuwhnqc= X-Google-Smtp-Source: ABdhPJzVH8qe7UX3d0c8lCZVjoyHR1+73SsttZNRuWCmfAgUF9OEmrsvds6dF79li+nJnxqCqmECggSLe4f6rFVyU/c= X-Received: by 2002:a05:6638:2257:: with SMTP id m23mr28073982jas.17.1637331335309; Fri, 19 Nov 2021 06:15:35 -0800 (PST) MIME-Version: 1.0 References: <20211118054426.4123-1-Kuan-Ying.Lee@mediatek.com> <754511d9a0368065768cc3ad8037184d62c3fbd1.camel@mediatek.com> In-Reply-To: <754511d9a0368065768cc3ad8037184d62c3fbd1.camel@mediatek.com> From: Andrey Konovalov Date: Fri, 19 Nov 2021 15:15:24 +0100 Message-ID: Subject: Re: [PATCH] kmemleak: fix kmemleak false positive report with HW tag-based kasan enable To: Kuan-Ying Lee Cc: Catalin Marinas , Andrew Morton , Matthias Brugger , =?UTF-8?B?Q2hpbndlbiBDaGFuZyAo5by16Yym5paHKQ==?= , =?UTF-8?B?TmljaG9sYXMgVGFuZyAo6YSt56em6LydKQ==?= , =?UTF-8?B?SmFtZXMgSHN1ICjlvpDmhbbolrAp?= , =?UTF-8?B?WWVlIExlZSAo5p2O5bu66Kq8KQ==?= , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mediatek@lists.infradead.org" , kasan-dev Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F3B893000117 X-Stat-Signature: 65sb85b6jmfc1hpb9fgtpcronyjak8js Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=TL+kYVRg; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf09.hostedemail.com: domain of andreyknvl@gmail.com designates 209.85.166.45 as permitted sender) smtp.mailfrom=andreyknvl@gmail.com X-HE-Tag: 1637331333-331053 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: 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. > > > > 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://groups.google.com/d/msgid/kasan-dev/754511d9a0368065768cc3ad8037184d62c3fbd1.camel%40mediatek.com.