4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Oleg Nesterov <o...@redhat.com>
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 <bbla...@plumgrid.com>
Signed-off-by: Oleg Nesterov <o...@redhat.com>
Reviewed-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Michal Hocko <mho...@kernel.org>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Alexei Starovoitov <alexei.starovoi...@gmail.com>
Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Vladimir Davydov <vdavy...@virtuozzo.com>
Fixes: 00501b531c47 ("mm: memcontrol: rewrite charge API")
Link: http://lkml.kernel.org/r/20160817153629.gb29...@redhat.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
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;
