linux-kernel - [PATCH v2] memcg, fsnotify: no oom-kill for remote memcg charging

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Sat,  4 May 2019 07:52:42 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Jan Kara <jack@...e.cz>,
        Amir Goldstein <amir73il@...il.com>
Cc:     linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH v2] memcg, fsnotify: no oom-kill for remote memcg charging

The 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.

Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
Changelog since v1:
- Fixed usage of __GFP_RETRY_MAYFAIL flag.

 fs/notify/fanotify/fanotify.c        | 5 ++++-
 fs/notify/inotify/inotify_fsnotify.c | 7 +++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 6b9c27548997..f78fd4c8f12d 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. Also make sure to not trigger OOM killer in the
+	 * target memcg for the limited size queues.
 	 */
 	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 ff30abd6a49b..17c08daa1ba7 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -99,9 +99,12 @@ 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. However
+	 * do not trigger the OOM killer in the target memcg.
+	 */
 	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)) {
-- 
2.21.0.1020.gf2820cf01a-goog