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[86.145.187.174]) by smtp.gmail.com with ESMTPSA id 34sm3971188wrh.78.2020.11.25.03.22.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Nov 2020 03:22:08 -0800 (PST) From: Lorenzo Stoakes To: Alex Shi , Johannes Weiner , Hui Su , Stephen Rothwell , Shakeel Butt , Roman Gushchin Cc: syzbot , Linux Kernel Mailing List , linux-mm , Linux-Next Mailing List , syzkaller-bugs , Lorenzo Stoakes Subject: [PATCH] mm/memcg: warn on missing memcg on mem_cgroup_page_lruvec() Date: Wed, 25 Nov 2020 11:22:02 +0000 Message-Id: <20201125112202.387009-1-lstoakes@gmail.com> X-Mailer: git-send-email 2.29.2 In-Reply-To: <00000000000054aea005b4d59e71@google.com> References: <00000000000054aea005b4d59e71@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Move memcg check to mem_cgroup_page_lruvec() as there are callers which may invoke this with !memcg in mem_cgroup_lruvec(), whereas they should not in mem_cgroup_page_lruvec(). We expect that we have always charged a page to the memcg before mem_cgroup_page_lruvec() is invoked, so add a warning to assert that this is the case. Signed-off-by: Lorenzo Stoakes Reported-by: syzbot+ce635500093181f39c1c@syzkaller.appspotmail.com --- include/linux/memcontrol.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 87ed56dc75f9..3e6a1df3bdb9 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -618,7 +618,6 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg, goto out; } - VM_WARN_ON_ONCE(!memcg); if (!memcg) memcg = root_mem_cgroup; @@ -645,7 +644,10 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg, static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgdat) { - return mem_cgroup_lruvec(page_memcg(page), pgdat); + struct mem_cgroup *memcg = page_memcg(page); + + VM_WARN_ON_ONCE_PAGE(!memcg, page); + return mem_cgroup_lruvec(memcg, pgdat); } static inline bool lruvec_holds_page_lru_lock(struct page *page, -- 2.29.2