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Reimplement RLIMIT_MSGQUEUE on top of ucounts

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The rlimit counter is tied to uid in the user_namespace. This allows
rlimit values to be specified in userns even if they are already
globally exceeded by the user. However, the value of the previous
user_namespaces cannot be exceeded.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/2531f42f7884bbfee56a978040b3e0d25cdf6cde.1619094428.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Alexey Gladkov 2021-04-22 14:27:12 +02:00 committed by Eric W. Biederman
parent 21d1c5e386
commit 6e52a9f053
6 changed files with 26 additions and 24 deletions
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4
include/linux/sched/user.h
View file

@ -18,10 +18,6 @@ struct user_struct {
#endif
#ifdef CONFIG_EPOLL
atomic_long_t epoll_watches; /* The number of file descriptors currently watched */
#endif
#ifdef CONFIG_POSIX_MQUEUE
/* protected by mq_lock */
unsigned long mq_bytes; /* How many bytes can be allocated to mqueue? */
#endif
unsigned long locked_shm; /* How many pages of mlocked shm ? */
unsigned long unix_inflight; /* How many files in flight in unix sockets */

1
include/linux/user_namespace.h
View file

@ -51,6 +51,7 @@ enum ucount_type {
UCOUNT_INOTIFY_WATCHES,
#endif
UCOUNT_RLIMIT_NPROC,
UCOUNT_RLIMIT_MSGQUEUE,
UCOUNT_COUNTS,
};

42
ipc/mqueue.c
View file

@ -144,7 +144,7 @@ struct mqueue_inode_info {
struct pid *notify_owner;
u32 notify_self_exec_id;
struct user_namespace *notify_user_ns;
struct user_struct *user; /* user who created, for accounting */
struct ucounts *ucounts; /* user who created, for accounting */
struct sock *notify_sock;
struct sk_buff *notify_cookie;
@ -292,7 +292,6 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
struct ipc_namespace *ipc_ns, umode_t mode,
struct mq_attr *attr)
{
struct user_struct *u = current_user();
struct inode *inode;
int ret = -ENOMEM;
@ -321,7 +320,7 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
info->notify_owner = NULL;
info->notify_user_ns = NULL;
info->qsize = 0;
info->user = NULL; /* set when all is ok */
info->ucounts = NULL; /* set when all is ok */
info->msg_tree = RB_ROOT;
info->msg_tree_rightmost = NULL;
info->node_cache = NULL;
@ -371,19 +370,23 @@ static struct inode *mqueue_get_inode(struct super_block *sb,
if (mq_bytes + mq_treesize < mq_bytes)
goto out_inode;
mq_bytes += mq_treesize;
spin_lock(&mq_lock);
if (u->mq_bytes + mq_bytes < u->mq_bytes ||
u->mq_bytes + mq_bytes > rlimit(RLIMIT_MSGQUEUE)) {
spin_unlock(&mq_lock);
/* mqueue_evict_inode() releases info->messages */
ret = -EMFILE;
goto out_inode;
}
u->mq_bytes += mq_bytes;
spin_unlock(&mq_lock);
info->ucounts = get_ucounts(current_ucounts());
if (info->ucounts) {
long msgqueue;
/* all is ok */
info->user = get_uid(u);
spin_lock(&mq_lock);
msgqueue = inc_rlimit_ucounts(info->ucounts, UCOUNT_RLIMIT_MSGQUEUE, mq_bytes);
if (msgqueue == LONG_MAX || msgqueue > rlimit(RLIMIT_MSGQUEUE)) {
dec_rlimit_ucounts(info->ucounts, UCOUNT_RLIMIT_MSGQUEUE, mq_bytes);
spin_unlock(&mq_lock);
put_ucounts(info->ucounts);
info->ucounts = NULL;
/* mqueue_evict_inode() releases info->messages */
ret = -EMFILE;
goto out_inode;
}
spin_unlock(&mq_lock);
}
} else if (S_ISDIR(mode)) {
inc_nlink(inode);
/* Some things misbehave if size == 0 on a directory */
@ -497,7 +500,6 @@ static void mqueue_free_inode(struct inode *inode)
static void mqueue_evict_inode(struct inode *inode)
{
struct mqueue_inode_info *info;
struct user_struct *user;
struct ipc_namespace *ipc_ns;
struct msg_msg *msg, *nmsg;
LIST_HEAD(tmp_msg);
@ -520,8 +522,7 @@ static void mqueue_evict_inode(struct inode *inode)
free_msg(msg);
}
user = info->user;
if (user) {
if (info->ucounts) {
unsigned long mq_bytes, mq_treesize;
/* Total amount of bytes accounted for the mqueue */
@ -533,7 +534,7 @@ static void mqueue_evict_inode(struct inode *inode)
info->attr.mq_msgsize);
spin_lock(&mq_lock);
user->mq_bytes -= mq_bytes;
dec_rlimit_ucounts(info->ucounts, UCOUNT_RLIMIT_MSGQUEUE, mq_bytes);
/*
* get_ns_from_inode() ensures that the
* (ipc_ns = sb->s_fs_info) is either a valid ipc_ns
@ -543,7 +544,8 @@ static void mqueue_evict_inode(struct inode *inode)
if (ipc_ns)
ipc_ns->mq_queues_count--;
spin_unlock(&mq_lock);
free_uid(user);
put_ucounts(info->ucounts);
info->ucounts = NULL;
}
if (ipc_ns)
put_ipc_ns(ipc_ns);

1
kernel/fork.c
View file

@ -823,6 +823,7 @@ void __init fork_init(void)
init_user_ns.ucount_max[i] = max_threads/2;
init_user_ns.ucount_max[UCOUNT_RLIMIT_NPROC] = task_rlimit(&init_task, RLIMIT_NPROC);
init_user_ns.ucount_max[UCOUNT_RLIMIT_MSGQUEUE] = task_rlimit(&init_task, RLIMIT_MSGQUEUE);
#ifdef CONFIG_VMAP_STACK
cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "fork:vm_stack_cache",

1
kernel/ucount.c
View file

@ -80,6 +80,7 @@ static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_inotify_instances"),
UCOUNT_ENTRY("max_inotify_watches"),
#endif
{ },
{ },
{ }
};

1
kernel/user_namespace.c
View file

@ -123,6 +123,7 @@ int create_user_ns(struct cred *new)
ns->ucount_max[i] = INT_MAX;
}
ns->ucount_max[UCOUNT_RLIMIT_NPROC] = rlimit(RLIMIT_NPROC);
ns->ucount_max[UCOUNT_RLIMIT_MSGQUEUE] = rlimit(RLIMIT_MSGQUEUE);
ns->ucounts = ucounts;
/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */