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mntns: Add a limit on the number of mount namespaces. 

v2: Fixed the very obvious lack of setting ucounts
    on struct mnt_ns reported by Andrei Vagin, and the kbuild
    test report.

Reported-by: Andrei Vagin <avagin@openvz.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2016-08-08 14:37:37 -05:00
parent 703286608a
commit 537f7ccb39
4 changed files with 24 additions and 1 deletions
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1
fs/mount.h
View File

@ -10,6 +10,7 @@ struct mnt_namespace {
struct mount * root;
struct list_head list;
struct user_namespace *user_ns;
struct ucounts *ucounts;
u64 seq; /* Sequence number to prevent loops */
wait_queue_head_t poll;
u64 event;

22
fs/namespace.c
View File

@ -2719,9 +2719,20 @@ long do_mount(const char *dev_name, const char __user *dir_name,
return retval;
}
static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
}
static void dec_mnt_namespaces(struct ucounts *ucounts)
{
dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
}
static void free_mnt_ns(struct mnt_namespace *ns)
{
ns_free_inum(&ns->ns);
dec_mnt_namespaces(ns->ucounts);
put_user_ns(ns->user_ns);
kfree(ns);
}
@ -2738,14 +2749,22 @@ static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
{
struct mnt_namespace *new_ns;
struct ucounts *ucounts;
int ret;
ucounts = inc_mnt_namespaces(user_ns);
if (!ucounts)
return ERR_PTR(-ENFILE);
new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
if (!new_ns)
if (!new_ns) {
dec_mnt_namespaces(ucounts);
return ERR_PTR(-ENOMEM);
}
ret = ns_alloc_inum(&new_ns->ns);
if (ret) {
kfree(new_ns);
dec_mnt_namespaces(ucounts);
return ERR_PTR(ret);
}
new_ns->ns.ops = &mntns_operations;
@ -2756,6 +2775,7 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
init_waitqueue_head(&new_ns->poll);
new_ns->event = 0;
new_ns->user_ns = get_user_ns(user_ns);
new_ns->ucounts = ucounts;
return new_ns;
}

1
include/linux/user_namespace.h
View File

@ -30,6 +30,7 @@ enum ucount_type {
UCOUNT_UTS_NAMESPACES,
UCOUNT_IPC_NAMESPACES,
UCOUNT_NET_NAMESPACES,
UCOUNT_MNT_NAMESPACES,
UCOUNT_CGROUP_NAMESPACES,
UCOUNT_COUNTS,
};

1
kernel/ucount.c
View File

@ -72,6 +72,7 @@ static struct ctl_table user_table[] = {
UCOUNT_ENTRY("max_uts_namespaces"),
UCOUNT_ENTRY("max_ipc_namespaces"),
UCOUNT_ENTRY("max_net_namespaces"),
UCOUNT_ENTRY("max_mnt_namespaces"),
UCOUNT_ENTRY("max_cgroup_namespaces"),
{ }
};