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(p200300cbc702dd00745e20b7bfa42e5f.dip0.t-ipconnect.de. [2003:cb:c702:dd00:745e:20b7:bfa4:2e5f]) by smtp.gmail.com with ESMTPSA id v11-20020a056000144b00b0020a9c02f60dsm1052532wrx.50.2022.04.22.00.39.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Apr 2022 00:39:38 -0700 (PDT) Message-ID: <3c218202-c4de-958c-8cf2-b0f24550d0d1@redhat.com> Date: Fri, 22 Apr 2022 09:39:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.2 Subject: Re: [PATCH] drivers/base/memory: Fix a reference counting issue in __add_memory_block() Content-Language: en-US To: Christophe JAILLET , Greg Kroah-Hartman , "Rafael J. Wysocki" , Scott Cheloha , Michal Hocko , Andrew Morton , Nathan Lynch Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org References: From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22.04.22 09:15, Christophe JAILLET wrote: > There is no point in doing put_device()/device_unregister() on a > device that has just been registered a few lines above. This will lead to > a double reference decrement. > > I guess that this put_device()/device_unregister() is a cut'n'paste from > remove_memory_block() (i.e. unregister_memory() at the time being) which > does need it. > > Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup") > Signed-off-by: Christophe JAILLET > --- > drivers/base/memory.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 7222ff9b5e05..084d67fd55cc 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory) > } > ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory, > GFP_KERNEL)); > - if (ret) { > - put_device(&memory->dev); > + if (ret) > device_unregister(&memory->dev); > - } > + > return ret; > } > Looks correct to me. I assume this will only happen once the stars align, but it's most certainly wrong I think. Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb