From abaed0112c1db08be15a784a2c5c8a8b3063cdd3 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Tue, 5 Nov 2019 21:16:40 -0800 Subject: [PATCH] mm, vmstat: hide /proc/pagetypeinfo from normal users /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. Link: http://lkml.kernel.org/r/20191025072610.18526-2-mhocko@kernel.org Fixes: 467c996c1e19 ("Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo") Signed-off-by: Michal Hocko Reported-by: Waiman Long Acked-by: Mel Gorman Acked-by: Vlastimil Babka Acked-by: Waiman Long Acked-by: Rafael Aquini Acked-by: David Rientjes Reviewed-by: Andrew Morton Cc: David Hildenbrand Cc: Johannes Weiner Cc: Roman Gushchin Cc: Konstantin Khlebnikov Cc: Jann Horn Cc: Song Liu Cc: Greg Kroah-Hartman Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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