Commit 6c4687cc authored Aug 17, 2016 by Oleg Nesterov Committed by Ingo Molnar Aug 18, 2016

uprobes: Fix the memcg accounting



__replace_page() wronlgy calls mem_cgroup_cancel_charge() in "success" path,
it should only do this if page_check_address() fails.

This means that every enable/disable leads to unbalanced mem_cgroup_uncharge()
from put_page(old_page), it is trivial to underflow the page_counter->count
and trigger OOM.

Reported-and-tested-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: stable@vger.kernel.org # 3.17+
Fixes: 00501b53 ("mm: memcontrol: rewrite charge API")
Link: http://lkml.kernel.org/r/20160817153629.GB29724@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 3cace81e

kernel/events/uprobes.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -172,8 +172,10 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
		mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
		err = -EAGAIN;
		ptep = page_check_address(page, mm, addr, &ptl, 0);
		if (!ptep)
		if (!ptep) {
		mem_cgroup_cancel_charge(kpage, memcg, false);
		goto unlock;
		}

		get_page(kpage);
		page_add_new_anon_rmap(kpage, vma, addr, false);
		@@ -200,7 +202,6 @@ static int __replace_page(struct vm_area_struct *vma, unsigned long addr,

		err = 0;
		unlock:
		mem_cgroup_cancel_charge(kpage, memcg, false);
		mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
		unlock_page(page);
		return err;

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