From: Shakeel Butt <shakeelb@xxxxxxxxxx>
Subject: memcg, fsnotify: no oom-kill for remote memcg charging
d46eb14b735b ("fs: fsnotify: account fsnotify metadata to kmemcg") added
remote memcg charging for fanotify and inotify event objects. The aim was
to charge the memory to the listener who is interested in the events but
without triggering the OOM killer. Otherwise there would be security
concerns for the listener. At the time, oom-kill trigger was not in the
charging path. A parallel work added the oom-kill back to charging path
i.e. commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the
charge path"). So to not trigger oom-killer in the remote memcg,
explicitly add __GFP_RETRY_MAYFAIL to the fanotigy and inotify event
allocations.
Link: http://lkml.kernel.org/r/20190514212259.156585-2-shakeelb@xxxxxxxxxx
Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Reviewed-by: Roman Gushchin <guro@xxxxxx>
Acked-by: Jan Kara <jack@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/notify/fanotify/fanotify.c | 5 ++++-
fs/notify/inotify/inotify_fsnotify.c | 8 ++++++--
2 files changed, 10 insertions(+), 3 deletions(-)
--- a/fs/notify/fanotify/fanotify.c~memcg-fsnotify-no-oom-kill-for-remote-memcg-charging
+++ a/fs/notify/fanotify/fanotify.c
@@ -288,10 +288,13 @@ struct fanotify_event *fanotify_alloc_ev
/*
* For queues with unlimited length lost events are not expected and
* can possibly have security implications. Avoid losing events when
- * memory is short.
+ * memory is short. For the limited size queues, avoid OOM killer in the
+ * target monitoring memcg as it may have security repercussion.
*/
if (group->max_events == UINT_MAX)
gfp |= __GFP_NOFAIL;
+ else
+ gfp |= __GFP_RETRY_MAYFAIL;
/* Whoever is interested in the event, pays for the allocation. */
memalloc_use_memcg(group->memcg);
--- a/fs/notify/inotify/inotify_fsnotify.c~memcg-fsnotify-no-oom-kill-for-remote-memcg-charging
+++ a/fs/notify/inotify/inotify_fsnotify.c
@@ -90,9 +90,13 @@ int inotify_handle_event(struct fsnotify
i_mark = container_of(inode_mark, struct inotify_inode_mark,
fsn_mark);
- /* Whoever is interested in the event, pays for the allocation. */
+ /*
+ * Whoever is interested in the event, pays for the allocation. Do not
+ * trigger OOM killer in the target monitoring memcg as it may have
+ * security repercussion.
+ */
memalloc_use_memcg(group->memcg);
- event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT);
+ event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
memalloc_unuse_memcg();
if (unlikely(!event)) {
_
