From ec165450968b26298bd1c373de37b0ab6d826b33 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Thu, 11 Jul 2019 20:55:52 -0700 Subject: memcg, fsnotify: no oom-kill for remote memcg charging Commit 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@google.com Signed-off-by: Shakeel Butt Reviewed-by: Roman Gushchin Acked-by: Jan Kara Cc: Johannes Weiner Cc: Vladimir Davydov Cc: Michal Hocko Cc: Amir Goldstein Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/notify/fanotify/fanotify.c | 5 ++++- fs/notify/inotify/inotify_fsnotify.c | 8 ++++++-- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index b428c295d13f..5778d1347b35 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -288,10 +288,13 @@ struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group, /* * 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); diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c index 2fda08b2b885..d510223d302c 100644 --- a/fs/notify/inotify/inotify_fsnotify.c +++ b/fs/notify/inotify/inotify_fsnotify.c @@ -90,9 +90,13 @@ int inotify_handle_event(struct fsnotify_group *group, 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)) { -- cgit v1.2.3