kernel/linux.git/net/core/net_namespace.c, branch v4.9.331

netns: add schedule point in ops_exit_list()

2022-01-27T07:47:41+00:00

commit 2836615aa22de55b8fca5e32fe1b27a67cda625e upstream. When under stress, cleanup_net() can have to dismantle netns in big numbers. ops_exit_list() currently calls many helpers [1] that have no schedule point, and we can end up with soft lockups, particularly on hosts with many cpus. Even for moderate amount of netns processed by cleanup_net() this patch avoids latency spikes. [1] Some of these helpers like fib_sync_up() and fib_sync_down_dev() are very slow because net/ipv4/fib_semantics.c uses host-wide hash tables, and ifindex is used as the only input of two hash functions. ifindexes tend to be the same for all netns (lo.ifindex==1 per instance) This will be fixed in a separate patch. Fixes: 72ad937abd0a ("net: Add support for batching network namespace cleanups") Signed-off-by: Eric Dumazet Cc: Eric W. Biederman Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

net/net_namespace: Check the return value of register_pernet_subsys()

2019-12-05T14:34:55+00:00

[ Upstream commit 0eb987c874dc93f9c9d85a6465dbde20fdd3884c ] In net_ns_init(), register_pernet_subsys() could fail while registering network namespace subsystems. The fix checks the return value and sends a panic() on failure. Signed-off-by: Aditya Pakki Reviewed-by: Kirill Tkhai Signed-off-by: David S. Miller Signed-off-by: Sasha Levin

netns: provide pure entropy for net_hash_mix()

2019-04-17T06:36:46+00:00

[ Upstream commit 355b98553789b646ed97ad801a619ff898471b92 ] net_hash_mix() currently uses kernel address of a struct net, and is used in many places that could be used to reveal this address to a patient attacker, thus defeating KASLR, for the typical case (initial net namespace, &init_net is not dynamically allocated) I believe the original implementation tried to avoid spending too many cycles in this function, but security comes first. Also provide entropy regardless of CONFIG_NET_NS. Fixes: 0b4419162aa6 ("netns: introduce the net_hash_mix "salt" for hashes") Signed-off-by: Eric Dumazet Reported-by: Amit Klein Reported-by: Benny Pinkas Cc: Pavel Emelyanov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

net: move somaxconn init from sysctl code

2018-04-13T17:48:06+00:00

[ Upstream commit 7c3f1875c66fbc19762760097cabc91849ea0bbb ] The default value for somaxconn is set in sysctl_core_net_init(), but this function is not called when kernel is configured without CONFIG_SYSCTL. This results in the kernel not being able to accept TCP connections, because the backlog has zero size. Usually, the user ends up with: "TCP: request_sock_TCP: Possible SYN flooding on port 7. Dropping request. Check SNMP counters." If SYN cookies are not enabled the connection is rejected. Before ef547f2ac16 (tcp: remove max_qlen_log), the effects were less severe, because the backlog was always at least eight slots long. Signed-off-by: Roman Kapl Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

net: Fix double free and memory corruption in get_net_ns_by_id()

2018-01-02T19:35:13+00:00

[ Upstream commit 21b5944350052d2583e82dd59b19a9ba94a007f0 ] (I can trivially verify that that idr_remove in cleanup_net happens after the network namespace count has dropped to zero --EWB) Function get_net_ns_by_id() does not check for net::count after it has found a peer in netns_ids idr. It may dereference a peer, after its count has already been finaly decremented. This leads to double free and memory corruption: put_net(peer) rtnl_lock() atomic_dec_and_test(&peer->count) [count=0] ... __put_net(peer) get_net_ns_by_id(net, id) spin_lock(&cleanup_list_lock) list_add(&net->cleanup_list, &cleanup_list) spin_unlock(&cleanup_list_lock) queue_work() peer = idr_find(&net->netns_ids, id) | get_net(peer) [count=1] | ... | (use after final put) v ... cleanup_net() ... spin_lock(&cleanup_list_lock) ... list_replace_init(&cleanup_list, ..) ... spin_unlock(&cleanup_list_lock) ... ... ... ... put_net(peer) ... atomic_dec_and_test(&peer->count) [count=0] ... spin_lock(&cleanup_list_lock) ... list_add(&net->cleanup_list, &cleanup_list) ... spin_unlock(&cleanup_list_lock) ... queue_work() ... rtnl_unlock() rtnl_lock() ... for_each_net(tmp) { ... id = __peernet2id(tmp, peer) ... spin_lock_irq(&tmp->nsid_lock) ... idr_remove(&tmp->netns_ids, id) ... ... ... net_drop_ns() ... net_free(peer) ... } ... | v cleanup_net() ... (Second free of peer) Also, put_net() on the right cpu may reorder with left's cpu list_replace_init(&cleanup_list, ..), and then cleanup_list will be corrupted. Since cleanup_net() is executed in worker thread, while put_net(peer) can happen everywhere, there should be enough time for concurrent get_net_ns_by_id() to pick the peer up, and the race does not seem to be unlikely. The patch fixes the problem in standard way. (Also, there is possible problem in peernet2id_alloc(), which requires check for net::count under nsid_lock and maybe_get_net(peer), but in current stable kernel it's used under rtnl_lock() and it has to be safe. Openswitch begun to use peernet2id_alloc(), and possibly it should be fixed too. While this is not in stable kernel yet, so I'll send a separate message to netdev@ later). Cc: Nicolas Dichtel Signed-off-by: Kirill Tkhai Fixes: 0c7aecd4bde4 "netns: add rtnl cmd to add and get peer netns ids" Reviewed-by: Andrey Ryabinin Reviewed-by: "Eric W. Biederman" Signed-off-by: Eric W. Biederman Reviewed-by: Eric Dumazet Acked-by: Nicolas Dichtel Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

net: check dead netns for peernet2id_alloc()

2016-11-17T16:19:40+00:00

Andrei reports we still allocate netns ID from idr after we destroy it in cleanup_net(). cleanup_net(): ... idr_destroy(&net->netns_ids); ... list_for_each_entry_reverse(ops, &pernet_list, list) ops_exit_list(ops, &net_exit_list); -> rollback_registered_many() -> rtmsg_ifinfo_build_skb() -> rtnl_fill_ifinfo() -> peernet2id_alloc() After that point we should not even access net->netns_ids, we should check the death of the current netns as early as we can in peernet2id_alloc(). For net-next we can consider to avoid sending rtmsg totally, it is a good optimization for netns teardown path. Fixes: 0c7aecd4bde4 ("netns: add rtnl cmd to add and get peer netns ids") Reported-by: Andrei Vagin Cc: Nicolas Dichtel Signed-off-by: Cong Wang Acked-by: Andrei Vagin Signed-off-by: Nicolas Dichtel Signed-off-by: David S. Miller

netns: revert "netns: avoid disabling irq for netns id"

2016-10-22T20:16:29+00:00

This reverts commit bc51dddf98c9 ("netns: avoid disabling irq for netns id") as it was found to cause problems with systems running SELinux/audit, see the mailing list thread below: * http://marc.info/?t=147694653900002&r=1&w=2 Eventually we should be able to reintroduce this code once we have rewritten the audit multicast code to queue messages much the same way we do for unicast messages. A tracking issue for this can be found below: * https://github.com/linux-audit/audit-kernel/issues/23 Reported-by: Stephen Smalley Reported-by: Elad Raz Cc: Cong Wang Signed-off-by: Paul Moore Signed-off-by: David S. Miller

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2016-10-06T16:52:23+00:00

Pull namespace updates from Eric Biederman: "This set of changes is a number of smaller things that have been overlooked in other development cycles focused on more fundamental change. The devpts changes are small things that were a distraction until we managed to kill off DEVPTS_MULTPLE_INSTANCES. There is an trivial regression fix to autofs for the unprivileged mount changes that went in last cycle. A pair of ioctls has been added by Andrey Vagin making it is possible to discover the relationships between namespaces when referring to them through file descriptors. The big user visible change is starting to add simple resource limits to catch programs that misbehave. With namespaces in general and user namespaces in particular allowing users to use more kinds of resources, it has become important to have something to limit errant programs. Because the purpose of these limits is to catch errant programs the code needs to be inexpensive to use as it always on, and the default limits need to be high enough that well behaved programs on well behaved systems don't encounter them. To this end, after some review I have implemented per user per user namespace limits, and use them to limit the number of namespaces. The limits being per user mean that one user can not exhause the limits of another user. The limits being per user namespace allow contexts where the limit is 0 and security conscious folks can remove from their threat anlysis the code used to manage namespaces (as they have historically done as it root only). At the same time the limits being per user namespace allow other parts of the system to use namespaces. Namespaces are increasingly being used in application sand boxing scenarios so an all or nothing disable for the entire system for the security conscious folks makes increasing use of these sandboxes impossible. There is also added a limit on the maximum number of mounts present in a single mount namespace. It is nontrivial to guess what a reasonable system wide limit on the number of mount structure in the kernel would be, especially as it various based on how a system is using containers. A limit on the number of mounts in a mount namespace however is much easier to understand and set. In most cases in practice only about 1000 mounts are used. Given that some autofs scenarious have the potential to be 30,000 to 50,000 mounts I have set the default limit for the number of mounts at 100,000 which is well above every known set of users but low enough that the mount hash tables don't degrade unreaonsably. These limits are a start. I expect this estabilishes a pattern that other limits for resources that namespaces use will follow. There has been interest in making inotify event limits per user per user namespace as well as interest expressed in making details about what is going on in the kernel more visible" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (28 commits) autofs: Fix automounts by using current_real_cred()->uid mnt: Add a per mount namespace limit on the number of mounts netns: move {inc,dec}_net_namespaces into #ifdef nsfs: Simplify __ns_get_path tools/testing: add a test to check nsfs ioctl-s nsfs: add ioctl to get a parent namespace nsfs: add ioctl to get an owning user namespace for ns file descriptor kernel: add a helper to get an owning user namespace for a namespace devpts: Change the owner of /dev/pts/ptmx to the mounter of /dev/pts devpts: Remove sync_filesystems devpts: Make devpts_kill_sb safe if fsi is NULL devpts: Simplify devpts_mount by using mount_nodev devpts: Move the creation of /dev/pts/ptmx into fill_super devpts: Move parse_mount_options into fill_super userns: When the per user per user namespace limit is reached return ENOSPC userns; Document per user per user namespace limits. mntns: Add a limit on the number of mount namespaces. netns: Add a limit on the number of net namespaces cgroupns: Add a limit on the number of cgroup namespaces ipcns: Add a limit on the number of ipc namespaces ...

netns: move {inc,dec}_net_namespaces into #ifdef

2016-09-23T18:39:43+00:00

With the newly enforced limit on the number of namespaces, we get a build warning if CONFIG_NETNS is disabled: net/core/net_namespace.c:273:13: error: 'dec_net_namespaces' defined but not used [-Werror=unused-function] net/core/net_namespace.c:268:24: error: 'inc_net_namespaces' defined but not used [-Werror=unused-function] This moves the two added functions inside the #ifdef that guards their callers. Fixes: 703286608a22 ("netns: Add a limit on the number of net namespaces") Signed-off-by: Arnd Bergmann Signed-off-by: Eric W. Biederman

Merge branch 'nsfs-ioctls' into HEAD

2016-09-23T01:00:36+00:00

From: Andrey Vagin Each namespace has an owning user namespace and now there is not way to discover these relationships. Pid and user namepaces are hierarchical. There is no way to discover parent-child relationships too. Why we may want to know relationships between namespaces? One use would be visualization, in order to understand the running system. Another would be to answer the question: what capability does process X have to perform operations on a resource governed by namespace Y? One more use-case (which usually called abnormal) is checkpoint/restart. In CRIU we are going to dump and restore nested namespaces. There [1] was a discussion about which interface to choose to determing relationships between namespaces. Eric suggested to add two ioctl-s [2]: > Grumble, Grumble. I think this may actually a case for creating ioctls > for these two cases. Now that random nsfs file descriptors are bind > mountable the original reason for using proc files is not as pressing. > > One ioctl for the user namespace that owns a file descriptor. > One ioctl for the parent namespace of a namespace file descriptor. Here is an implementaions of these ioctl-s. $ man man7/namespaces.7 ... Since Linux 4.X, the following ioctl(2) calls are supported for namespace file descriptors. The correct syntax is: fd = ioctl(ns_fd, ioctl_type); where ioctl_type is one of the following: NS_GET_USERNS Returns a file descriptor that refers to an owning user names‐ pace. NS_GET_PARENT Returns a file descriptor that refers to a parent namespace. This ioctl(2) can be used for pid and user namespaces. For user namespaces, NS_GET_PARENT and NS_GET_USERNS have the same meaning. In addition to generic ioctl(2) errors, the following specific ones can occur: EINVAL NS_GET_PARENT was called for a nonhierarchical namespace. EPERM The requested namespace is outside of the current namespace scope. [1] https://lkml.org/lkml/2016/7/6/158 [2] https://lkml.org/lkml/2016/7/9/101 Changes for v2: * don't return ENOENT for init_user_ns and init_pid_ns. There is nothing outside of the init namespace, so we can return EPERM in this case too. > The fewer special cases the easier the code is to get > correct, and the easier it is to read. // Eric Changes for v3: * rename ns->get_owner() to ns->owner(). get_* usually means that it grabs a reference. Cc: "Eric W. Biederman" Cc: James Bottomley Cc: "Michael Kerrisk (man-pages)" Cc: "W. Trevor King" Cc: Alexander Viro Cc: Serge Hallyn