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[169.235.26.74]) by smtp.googlemail.com with ESMTPSA id b123sm44863606pfg.64.2019.08.21.23.21.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Aug 2019 23:21:49 -0700 (PDT) From: Yizhuo To: Cc: csong@cs.ucr.edu, zhiyunq@cs.ucr.edu, Yizhuo , Johannes Weiner , Michal Hocko , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] mm/memcg: return value of the function mem_cgroup_from_css() is not checked Date: Wed, 21 Aug 2019 23:22:09 -0700 Message-Id: <20190822062210.18649-1-yzhai003@ucr.edu> X-Mailer: git-send-email 2.17.1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000460, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Inside function mem_cgroup_wb_domain(), the pointer memcg could be NULL via mem_cgroup_from_css(). However, this pointer is not checked and directly dereferenced in the if statement, which is potentially unsafe. Signed-off-by: Yizhuo --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 661f046ad318..bd84bdaed3b0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3665,7 +3665,7 @@ struct wb_domain *mem_cgroup_wb_domain(struct bdi_writeback *wb) { struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css); - if (!memcg->css.parent) + if (!memcg || !memcg->css.parent) return NULL; return &memcg->cgwb_domain; -- 2.17.1