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[109.252.193.60]) by smtp.googlemail.com with ESMTPSA id y10sm332353lfl.240.2021.03.24.12.49.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Mar 2021 12:49:59 -0700 (PDT) Subject: Re: [PATCH] mm: cma: fix corruption cma_sysfs_alloc_pages_count From: Dmitry Osipenko To: Minchan Kim , Andrew Morton Cc: linux-mm , LKML , gregkh@linuxfoundation.org, surenb@google.com, joaodias@google.com, jhubbard@nvidia.com, willy@infradead.org References: <20210324192044.1505747-1-minchan@kernel.org> <18ee5c3e-fba2-0d8d-bd93-5fb8d0dd7a01@gmail.com> Message-ID: <89ba4c7a-42d2-5412-2367-cc1cffc1117b@gmail.com> Date: Wed, 24 Mar 2021 22:49:58 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <18ee5c3e-fba2-0d8d-bd93-5fb8d0dd7a01@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 1328C2000249 X-Stat-Signature: iy1w9hawjbzfhb77dhza8r8tja6a78a7 Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf11; identity=mailfrom; envelope-from=""; helo=mail-lf1-f41.google.com; client-ip=209.85.167.41 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616615398-653949 Content-Transfer-Encoding: quoted-printable 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: 24.03.2021 22:43, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > 24.03.2021 22:20, Minchan Kim =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> static int __init cma_sysfs_init(void) >> { >> - int i =3D 0; >> + struct kobject *cma_kobj_root; >> + struct cma_kobject *cma_kobj; >> struct cma *cma; >> + unsigned int i; >=20 >> while (--i >=3D 0) { >=20 > Do you realize that this doesn't work anymore? >=20 >> cma =3D &cma_areas[i]; >> - kobject_put(&cma->stat->kobj); >> - } >> =20 >> - kfree(cma_stats); >> - kobject_put(cma_kobj); >> + kobject_put(&cma->cma_kobj->kobj); >> + kfree(cma->cma_kobj); >=20 > Freeing a null pointer? >=20 >> + cma->cma_kobj =3D NULL; >> + } >> + kobject_put(cma_kobj_root); >=20 Please try to simulate the errors and check that error path is working properly in the next version. Alternatively, we could remove the cma_kobj_release entirely, like Greg suggested previously, and then don't care about cleaning up at all.