Commit abaed011 authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds

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: 467c996c ("Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo")
Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Reported-by: default avatarWaiman Long <longman@redhat.com>
Acked-by: default avatarMel Gorman <mgorman@suse.de>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarWaiman Long <longman@redhat.com>
Acked-by: default avatarRafael Aquini <aquini@redhat.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Jann Horn <jannh@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent df2ec764
......@@ -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
......
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