4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Oleg Nesterov <[email protected]> commit 6c4687cc17a788a6dd8de3e27dbeabb7cbd3e066 upstream. __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 <[email protected]> Signed-off-by: Oleg Nesterov <[email protected]> Reviewed-by: Johannes Weiner <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Alexander Shishkin <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Vladimir Davydov <[email protected]> Fixes: 00501b531c47 ("mm: memcontrol: rewrite charge API") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/events/uprobes.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -171,8 +171,10 @@ static int __replace_page(struct vm_area 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); goto unlock; + } get_page(kpage); page_add_new_anon_rmap(kpage, vma, addr); @@ -199,7 +201,6 @@ static int __replace_page(struct vm_area err = 0; unlock: - mem_cgroup_cancel_charge(kpage, memcg); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); unlock_page(page); return err;
