From c3d532008661da197997fc6d8098190eef9344ad Mon Sep 17 00:00:00 2001 From: Chris Down Date: Wed, 1 Apr 2020 21:07:27 -0700 Subject: mm, memcg: prevent memory.min load/store tearing This can be set concurrently with reads, which may cause the wrong value to be propagated. Signed-off-by: Chris Down Signed-off-by: Andrew Morton Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Roman Gushchin Cc: Tejun Heo Link: http://lkml.kernel.org/r/e809b4e6b0c1626dac6945970de06409a180ee65.1584034301.git.chris@chrisdown.name Signed-off-by: Linus Torvalds --- mm/page_counter.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'mm/page_counter.c') diff --git a/mm/page_counter.c b/mm/page_counter.c index 509143f232d8..c56db2d5e159 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -17,14 +17,15 @@ static void propagate_protected_usage(struct page_counter *c, unsigned long usage) { unsigned long protected, old_protected; - unsigned long low; + unsigned long low, min; long delta; if (!c->parent) return; - if (c->min || atomic_long_read(&c->min_usage)) { - protected = min(usage, c->min); + min = READ_ONCE(c->min); + if (min || atomic_long_read(&c->min_usage)) { + protected = min(usage, min); old_protected = atomic_long_xchg(&c->min_usage, protected); delta = protected - old_protected; if (delta) @@ -207,7 +208,7 @@ void page_counter_set_min(struct page_counter *counter, unsigned long nr_pages) { struct page_counter *c; - counter->min = nr_pages; + WRITE_ONCE(counter->min, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); -- cgit v1.2.3