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Tue, 07 Jun 2022 07:36:13 -0700 (PDT) Message-ID: Date: Tue, 7 Jun 2022 22:36:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH v2 3/4] mm: kmemleak: handle address stored in object based on its type Content-Language: en-US To: Catalin Marinas Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yee.lee@mediatek.com References: <20220603035415.1243913-1-patrick.wang.shcn@gmail.com> <20220603035415.1243913-4-patrick.wang.shcn@gmail.com> From: Patrick Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=Hu1mE7Dz; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf13.hostedemail.com: domain of patrick.wang.shcn@gmail.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=patrick.wang.shcn@gmail.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 2F3C520027 X-Rspam-User: X-Stat-Signature: nocpo4b31xsxr131h53npi4ps64a3bht X-HE-Tag: 1654612536-379502 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 2022/6/6 23:01, Catalin Marinas wrote: > On Fri, Jun 03, 2022 at 11:54:14AM +0800, Patrick Wang wrote: >> Treat the address stored in object in different way according >> to its type: >> >> - Only use kasan_reset_tag for virtual address >> - Only update min_addr and max_addr for virtual address >> - Convert physical address to virtual address in scan_object >> >> Suggested-by: Catalin Marinas >> Signed-off-by: Patrick Wang >> --- >> mm/kmemleak.c | 34 ++++++++++++++++++++++++---------- >> 1 file changed, 24 insertions(+), 10 deletions(-) >> >> diff --git a/mm/kmemleak.c b/mm/kmemleak.c >> index 218144392446..246a70b7218f 100644 >> --- a/mm/kmemleak.c >> +++ b/mm/kmemleak.c >> @@ -297,7 +297,9 @@ static void hex_dump_object(struct seq_file *seq, >> warn_or_seq_printf(seq, " hex dump (first %zu bytes):\n", len); >> kasan_disable_current(); >> warn_or_seq_hex_dump(seq, DUMP_PREFIX_NONE, HEX_ROW_SIZE, >> - HEX_GROUP_SIZE, kasan_reset_tag((void *)ptr), len, HEX_ASCII); >> + HEX_GROUP_SIZE, object->flags & OBJECT_PHYS ? ptr : >> + kasan_reset_tag((void *)ptr), >> + len, HEX_ASCII); >> kasan_enable_current(); >> } > > This will go wrong since ptr is the actual physical address, it cannot > be dereferenced. This should only be used on virtual pointers and this > is the case already as we never print unreferenced objects from the phys > tree. What we could do though is something like an early exit from this > function (together with a comment that it doesn't support dumping such > objects): > > if (WARN_ON_ONCE(object->flags & OBJECT_PHYS)) > return; > I also found this. Will do. >> >> @@ -389,14 +391,15 @@ static struct kmemleak_object *lookup_object(unsigned long ptr, int alias, >> { >> struct rb_node *rb = is_phys ? object_phys_tree_root.rb_node : >> object_tree_root.rb_node; >> - unsigned long untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr); >> + unsigned long untagged_ptr = is_phys ? ptr : (unsigned long)kasan_reset_tag((void *)ptr); >> >> while (rb) { >> struct kmemleak_object *object; >> unsigned long untagged_objp; >> >> object = rb_entry(rb, struct kmemleak_object, rb_node); >> - untagged_objp = (unsigned long)kasan_reset_tag((void *)object->pointer); >> + untagged_objp = is_phys ? object->pointer : >> + (unsigned long)kasan_reset_tag((void *)object->pointer); >> >> if (untagged_ptr < untagged_objp) >> rb = object->rb_node.rb_left; > > You could leave this unchanged. A phys pointer is already untagged, so > it wouldn't make any difference. Right, will do. > >> @@ -643,16 +646,19 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size, >> >> raw_spin_lock_irqsave(&kmemleak_lock, flags); >> >> - untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr); >> - min_addr = min(min_addr, untagged_ptr); >> - max_addr = max(max_addr, untagged_ptr + size); >> + untagged_ptr = is_phys ? ptr : (unsigned long)kasan_reset_tag((void *)ptr); > > Same here. Will do. > >> + if (!is_phys) { >> + min_addr = min(min_addr, untagged_ptr); >> + max_addr = max(max_addr, untagged_ptr + size); >> + } >> link = is_phys ? &object_phys_tree_root.rb_node : >> &object_tree_root.rb_node; >> rb_parent = NULL; >> while (*link) { >> rb_parent = *link; >> parent = rb_entry(rb_parent, struct kmemleak_object, rb_node); >> - untagged_objp = (unsigned long)kasan_reset_tag((void *)parent->pointer); >> + untagged_objp = is_phys ? parent->pointer : >> + (unsigned long)kasan_reset_tag((void *)parent->pointer); > > And here. Will do. > >> if (untagged_ptr + size <= untagged_objp) >> link = &parent->rb_node.rb_left; >> else if (untagged_objp + parent->size <= untagged_ptr) >> @@ -1202,7 +1208,9 @@ static bool update_checksum(struct kmemleak_object *object) >> >> kasan_disable_current(); >> kcsan_disable_current(); >> - object->checksum = crc32(0, kasan_reset_tag((void *)object->pointer), object->size); >> + object->checksum = crc32(0, object->flags & OBJECT_PHYS ? (void *)object->pointer : >> + kasan_reset_tag((void *)object->pointer), >> + object->size); > > Luckily that's never called on a phys object, otherwise *object->pointer > would segfault. As for hex_dump, just return early with a warning if > that's the case. Right, will do. Thanks, Patrick