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Date: Wed, 1 Jun 2016 10:52:57 +0300
From: Nikolay Borisov <kernel@...p.com>
To: john@...nmccutchan.com, eparis@...hat.com, ebiederm@...ssion.com
Cc: jack@...e.cz, linux-kernel@...r.kernel.org, gorcunov@...nvz.org,
avagin@...nvz.org, netdev@...r.kernel.org,
operations@...eground.com, Nikolay Borisov <kernel@...p.com>
Subject: [PATCH 1/4] inotify: Add infrastructure to account inotify limits per-namespace
This patch adds the necessary members to user_struct. The idea behind
the solution is really simple - user the userns pointers as keys into
a hash table which holds the inotify instances/watches counts. This
allows to account the limits per userns rather than per real user,
which makes certain scenarios such as a single mapped user in a
container deplete the inotify resources for all other users, which
map to the exact same real user.
Signed-off-by: Nikolay Borisov <kernel@...p.com>
---
fs/notify/inotify/inotify.h | 68 ++++++++++++++++++++++++++++++++++++++++
fs/notify/inotify/inotify_user.c | 36 +++++++++++++++++++++
include/linux/fsnotify_backend.h | 1 +
include/linux/sched.h | 3 ++
kernel/user.c | 13 ++++++++
5 files changed, 121 insertions(+)
diff --git a/fs/notify/inotify/inotify.h b/fs/notify/inotify/inotify.h
index ed855ef6f077..e069e1e4262a 100644
--- a/fs/notify/inotify/inotify.h
+++ b/fs/notify/inotify/inotify.h
@@ -1,6 +1,7 @@
#include <linux/fsnotify_backend.h>
#include <linux/inotify.h>
#include <linux/slab.h> /* struct kmem_cache */
+#include <linux/hashtable.h>
struct inotify_event_info {
struct fsnotify_event fse;
@@ -15,6 +16,13 @@ struct inotify_inode_mark {
int wd;
};
+struct inotify_state {
+ struct hlist_node node;
+ void *key; /* user_namespace ptr */
+ u32 inotify_watches; /* How many inotify watches does this user have? */
+ u32 inotify_devs; /* How many inotify devs does this user have opened? */
+};
+
static inline struct inotify_event_info *INOTIFY_E(struct fsnotify_event *fse)
{
return container_of(fse, struct inotify_event_info, fse);
@@ -30,3 +38,63 @@ extern int inotify_handle_event(struct fsnotify_group *group,
const unsigned char *file_name, u32 cookie);
extern const struct fsnotify_ops inotify_fsnotify_ops;
+
+/* Helpers for manipulating various inotify state, stored in user_struct */
+static inline struct inotify_state *__find_inotify_state(struct user_struct *user,
+ void *key)
+{
+ struct inotify_state *state;
+
+ hash_for_each_possible(user->inotify_tbl, state, node, (unsigned long)key)
+ if (state->key == key)
+ return state;
+
+ return NULL;
+}
+
+static inline void inotify_inc_watches(struct user_struct *user, void *key)
+{
+ struct inotify_state *state;
+
+ spin_lock(&user->inotify_lock);
+ state = __find_inotify_state(user, key);
+ state->inotify_watches++;
+ spin_unlock(&user->inotify_lock);
+}
+
+
+static inline void inotify_dec_watches(struct user_struct *user, void *key)
+{
+ struct inotify_state *state;
+
+ spin_lock(&user->inotify_lock);
+ state = __find_inotify_state(user, key);
+ state->inotify_watches--;
+ spin_unlock(&user->inotify_lock);
+}
+
+static inline int inotify_read_watches(struct user_struct *user, void *key)
+{
+ struct inotify_state *state;
+ int ret;
+
+ spin_lock(&user->inotify_lock);
+ state = __find_inotify_state(user, key);
+ ret = state->inotify_watches;
+ spin_unlock(&user->inotify_lock);
+ return ret;
+}
+
+static inline unsigned long inotify_dec_return_dev(struct user_struct *user,
+ void *key)
+{
+ struct inotify_state *state;
+ unsigned long ret;
+
+ spin_lock(&user->inotify_lock);
+ state = __find_inotify_state(user, key);
+ ret = --state->inotify_devs;
+ spin_unlock(&user->inotify_lock);
+
+ return ret;
+}
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index b8d08d0d0a4d..ae7ec2414252 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -86,6 +86,42 @@ struct ctl_table inotify_table[] = {
};
#endif /* CONFIG_SYSCTL */
+
+static int inotify_init_state(struct user_struct *user,
+ void *key)
+{
+ struct inotify_state *state;
+ int ret = 0;
+
+ spin_lock(&user->inotify_lock);
+ state = __find_inotify_count(user, key);
+
+ if (!state) {
+ spin_unlock(&user->inotify_lock);
+ state = kzalloc(sizeof(struct inotify_state), GFP_KERNEL);
+ if (!state)
+ return -ENOMEM;
+
+ state->key = current_user_ns();
+ state->inotify_watches = 0;
+ state->inotify_devs = 1;
+
+ spin_lock(&user->inotify_lock);
+ hash_add(user->inotify_tbl, &state->node, (unsigned long)key);
+
+ goto out;
+ } else {
+
+ if (++state->inotify_devs > inotify_max_user_instances) {
+ ret = -EMFILE;
+ goto out;
+ }
+ }
+out:
+ spin_unlock(&user->inotify_lock);
+ return ret;
+}
+
static inline __u32 inotify_arg_to_mask(u32 arg)
{
__u32 mask;
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 29f917517299..89f7c247b038 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -170,6 +170,7 @@ struct fsnotify_group {
spinlock_t idr_lock;
struct idr idr;
struct user_struct *user;
+ void *userns_ptr;
} inotify_data;
#endif
#ifdef CONFIG_FANOTIFY
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6e42ada26345..0c55d951d0bb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -58,6 +58,7 @@ struct sched_param {
#include <linux/uidgid.h>
#include <linux/gfp.h>
#include <linux/magic.h>
+#include <linux/hashtable.h>
#include <linux/cgroup-defs.h>
#include <asm/processor.h>
@@ -839,6 +840,8 @@ struct user_struct {
atomic_t processes; /* How many processes does this user have? */
atomic_t sigpending; /* How many pending signals does this user have? */
#ifdef CONFIG_INOTIFY_USER
+ spinlock_t inotify_lock;
+ DECLARE_HASHTABLE(inotify_tbl, 6);
atomic_t inotify_watches; /* How many inotify watches does this user have? */
atomic_t inotify_devs; /* How many inotify devs does this user have opened? */
#endif
diff --git a/kernel/user.c b/kernel/user.c
index b069ccbfb0b0..0c73b0318806 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -17,6 +17,8 @@
#include <linux/export.h>
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>
+#include <linux/hashtable.h>
+
/*
* userns count is 1 for root user, 1 for init_uts_ns,
@@ -94,6 +96,9 @@ struct user_struct root_user = {
.sigpending = ATOMIC_INIT(0),
.locked_shm = 0,
.uid = GLOBAL_ROOT_UID,
+#ifdef CONFIG_INOTIFY_USER
+ .inotify_lock = __SPIN_LOCK_UNLOCKED(root_user.inotify_lock),
+#endif
};
/*
@@ -184,6 +189,10 @@ struct user_struct *alloc_uid(kuid_t uid)
new->uid = uid;
atomic_set(&new->__count, 1);
+#ifdef CONFIG_INOTIFY_USER
+ spin_lock_init(&new->inotify_lock);
+ hash_init(new->inotify_tbl);
+#endif
/*
* Before adding this, check whether we raced
@@ -223,6 +232,10 @@ static int __init uid_cache_init(void)
uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
spin_unlock_irq(&uidhash_lock);
+#ifdef CONFIG_INOTIFY_USER
+ hash_init(root_user.inotify_tbl);
+#endif
+
return 0;
}
subsys_initcall(uid_cache_init);
--
2.5.0
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