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[37.188.173.3]) by smtp.gmail.com with ESMTPSA id u21sm18234122wmu.27.2019.10.23.03.27.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Oct 2019 03:27:50 -0700 (PDT) From: Michal Hocko To: Andrew Morton , Mel Gorman , Waiman Long Cc: Johannes Weiner , Roman Gushchin , Vlastimil Babka , Konstantin Khlebnikov , Jann Horn , Song Liu , Greg Kroah-Hartman , Rafael Aquini , , LKML , Michal Hocko Subject: [RFC PATCH 1/2] mm, vmstat: hide /proc/pagetypeinfo from normal users Date: Wed, 23 Oct 2019 12:27:36 +0200 Message-Id: <20191023102737.32274-2-mhocko@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191023102737.32274-1-mhocko@kernel.org> References: <20191023095607.GE3016@techsingularity.net> <20191023102737.32274-1-mhocko@kernel.org> MIME-Version: 1.0 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: From: Michal Hocko /proc/pagetypeinfo is a debugging tool to examine internal page allocator state wrt to fragmentation. It is not very useful for any other use so normal users really do not need to read this file. Waiman Long has noticed that reading this file can have negative side effects because zone->lock is necessary for gathering data and that a) interferes with the page allocator and its users and b) can lead to hard lockups on large machines which have very long free_list. Reduce both issues by simply not exporting the file to regular users. Reported-by: Waiman Long Cc: stable Signed-off-by: Michal Hocko --- mm/vmstat.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index 6afc892a148a..4e885ecd44d1 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1972,7 +1972,7 @@ void __init init_mm_internals(void) #endif #ifdef CONFIG_PROC_FS proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op); - proc_create_seq("pagetypeinfo", 0444, NULL, &pagetypeinfo_op); + proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op); proc_create_seq("vmstat", 0444, NULL, &vmstat_op); proc_create_seq("zoneinfo", 0444, NULL, &zoneinfo_op); #endif --=20 2.20.1