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[203.206.37.215]) by smtp.gmail.com with ESMTPSA id 196sm12926660pfz.99.2019.10.04.20.11.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Oct 2019 20:11:14 -0700 (PDT) Subject: Re: [PATCH] kmemleak: Do not corrupt the object_list during clean-up To: Catalin Marinas , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Marc Dionne , Andrew Morton References: <20191004134624.46216-1-catalin.marinas@arm.com> From: Alexey Kardashevskiy Autocrypt: addr=aik@ozlabs.ru; keydata= mQINBE+rT0sBEADFEI2UtPRsLLvnRf+tI9nA8T91+jDK3NLkqV+2DKHkTGPP5qzDZpRSH6mD EePO1JqpVuIow/wGud9xaPA5uvuVgRS1q7RU8otD+7VLDFzPRiRE4Jfr2CW89Ox6BF+q5ZPV /pS4v4G9eOrw1v09lEKHB9WtiBVhhxKK1LnUjPEH3ifkOkgW7jFfoYgTdtB3XaXVgYnNPDFo PTBYsJy+wr89XfyHr2Ev7BB3Xaf7qICXdBF8MEVY8t/UFsesg4wFWOuzCfqxFmKEaPDZlTuR tfLAeVpslNfWCi5ybPlowLx6KJqOsI9R2a9o4qRXWGP7IwiMRAC3iiPyk9cknt8ee6EUIxI6 t847eFaVKI/6WcxhszI0R6Cj+N4y+1rHfkGWYWupCiHwj9DjILW9iEAncVgQmkNPpUsZECLT 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XrB5p+6ML7Bd84xOEGsj/vdaXmz1esuH7BOZAGEZfLRCHJ0GVCSssg== Message-ID: <5a75249e-47ee-bb7c-d281-31b385d8bb86@ozlabs.ru> Date: Sat, 5 Oct 2019 13:11:10 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191004134624.46216-1-catalin.marinas@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 04/10/2019 23:46, Catalin Marinas wrote: > In case of an error (e.g. memory pool too small), kmemleak disables > itself and cleans up the already allocated metadata objects. However, if > this happens early before the RCU callback mechanism is available, > put_object() skips call_rcu() and frees the object directly. This is not > safe with the RCU list traversal in __kmemleak_do_cleanup(). > > Change the list traversal in __kmemleak_do_cleanup() to > list_for_each_entry_safe() and remove the rcu_read_{lock,unlock} since > the kmemleak is already disabled at this point. In addition, avoid an > unnecessary metadata object rb-tree look-up since it already has the > struct kmemleak_object pointer. > > Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations") > Reported-by: Alexey Kardashevskiy > Reported-by: Marc Dionne > Cc: Andrew Morton > Signed-off-by: Catalin Marinas Tested-by: Alexey Kardashevskiy It not just fixed lockups but brought network speed back to normal but I guess it is because kmemleak disables itself when CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE=400. dmesg: [ 0.000000] kmemleak: Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE [ 0.000000] kmemleak: Cannot allocate a kmemleak_object structure [ 0.000000] kmemleak: Kernel memory leak detector disabled > --- > mm/kmemleak.c | 30 +++++++++++++++++++++--------- > 1 file changed, 21 insertions(+), 9 deletions(-) > > diff --git a/mm/kmemleak.c b/mm/kmemleak.c > index 03a8d84badad..244607663363 100644 > --- a/mm/kmemleak.c > +++ b/mm/kmemleak.c > @@ -526,6 +526,16 @@ static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias) > return object; > } > > +/* > + * Remove an object from the object_tree_root and object_list. Must be called > + * with the kmemleak_lock held _if_ kmemleak is still enabled. > + */ > +static void __remove_object(struct kmemleak_object *object) > +{ > + rb_erase(&object->rb_node, &object_tree_root); > + list_del_rcu(&object->object_list); > +} > + > /* > * Look up an object in the object search tree and remove it from both > * object_tree_root and object_list. The returned object's use_count should be > @@ -538,10 +548,8 @@ static struct kmemleak_object *find_and_remove_object(unsigned long ptr, int ali > > write_lock_irqsave(&kmemleak_lock, flags); > object = lookup_object(ptr, alias); > - if (object) { > - rb_erase(&object->rb_node, &object_tree_root); > - list_del_rcu(&object->object_list); > - } > + if (object) > + __remove_object(object); > write_unlock_irqrestore(&kmemleak_lock, flags); > > return object; > @@ -1834,12 +1842,16 @@ static const struct file_operations kmemleak_fops = { > > static void __kmemleak_do_cleanup(void) > { > - struct kmemleak_object *object; > + struct kmemleak_object *object, *tmp; > > - rcu_read_lock(); > - list_for_each_entry_rcu(object, &object_list, object_list) > - delete_object_full(object->pointer); > - rcu_read_unlock(); > + /* > + * Kmemleak has already been disabled, no need for RCU list traversal > + * or kmemleak_lock held. > + */ > + list_for_each_entry_safe(object, tmp, &object_list, object_list) { > + __remove_object(object); > + __delete_object(object); > + } > } > > /* > -- Alexey