[RHEL7,COMMIT] tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of tun device

Submitted by Konstantin Khorenko on June 11, 2020, 4:20 p.m.

Details

Message ID 202006111620.05BGKKvt022512@finist-ce7.sw.ru
State New
Series "port nsfs from vz8"
Headers show

Commit Message

Konstantin Khorenko June 11, 2020, 4:20 p.m.
The commit is pushed to "branch-rh7-3.10.0-1127.10.1.vz7.162.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.10.1.vz7.162.2
------>
commit 1cc38b7a5bb59dd204f4657e77ffcc7d3062acaf
Author: Kirill Tkhai <ktkhai@virtuozzo.com>
Date:   Thu Jun 11 19:20:20 2020 +0300

    tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of tun device
    
    This patch adds possibility to get tun device's net namespace fd
    in the same way we allow to do that for sockets.
    
    Socket ioctl numbers do not intersect with tun-specific, and there
    is already SIOCSIFHWADDR used in tun code. So, SIOCGSKNS number
    is choosen instead of custom-made for this functionality.
    
    Note, that open_related_ns() uses plain get_net_ns() and it's safe
    (net can't be already dead at this moment):
    
      tun socket is allocated via sk_alloc() with zero last arg (kern = 0).
      So, each alive socket increments net::count, and the socket is definitely
      alive during ioctl syscall.
    
    Also, common variable net is introduced, so small cleanup in TUNSETIFF
    is made.
    
    Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
    
    Signed-off-by: David S. Miller <davem@davemloft.net>
    
    While on it also fix inconsistency with MS behaviour: TUNSETIFF should
    return EEXIST if tun exists.
    
    (cherry picked from commit f2780d6d74756bc1d7ba32ff3dd0de4afd7c7e1e)
    
    https://jira.sw.ru/browse/PSBM-102357
    
    Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
    
    =====================
    Patchset description:
    port nsfs from vz8
    
    We have problems with /proc/pid/ns/name bind-mounts in CRIU
    
    1) Currently (without nsfs) such a bind mount have same superblock with
    /proc mount, but in case of nested pid-namespaces container can have
    multiple different /proc mounts and for ns-bind-mount we need to bind it
    from the right pidns. So we will need to enter proper pid-namespace to
    reopen ns-file fd from proper proc, it looks too complex.
    
    If we port nsfs ns-bind-mounts will be all on the same superblock which
    does not depend from procfs's we opened the ns-file on.
    
    2) Bigger problem will come then we will wan't to migrate ns-bind-mounts
    from non-nsfs to nsfs (vz8) kernel this would bring a lot of crutches,
    we will need to workaround the fact that before migration mounts were
    with same superblock and after migration they can't be.
    
    To overcome those we can port nsfs to vz7 and do ns-bind-mount support in
    a new world of nsfs, looks like it would be easier.
    
    First we need to revert all patches which depend from nsfs:
    
    8782a0069f1b proc: add a proc_show_path method to fix mountinfo
    b823f8df2fcb ms/tun: Add ioctl() TUNGETDEVNETNS cmd to allow obtaining real net ns of tun device
    302889fa2e3d ms/net: add an ioctl to get a socket network namespace
    7cb9e7ae7041 ms/tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of tun device
    ac08c64138ac nsfs: add ioctl to get a parent namespace
    a8e0dd94d5cd nsfs: add ioctl to get an owning user namespace for ns file descriptor
    93dca538d184 kernel: add a helper to get an owning user namespace for a namespace
    edaecdb8adac ms/pidns: expose task pid_ns_for_children to userspace
    2b151c3f8909 ms/ns: allow ns_entries to have custom symlink content
    
    Cherry-pick nsfs from VZ8:
    
    435d5f4bb2cc common object embedded into various struct ....ns
    58be28256d98 make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns
    ff24870f46d5 netns: switch ->get()/->put()/->install()/->inum() to working with &net->ns
    3c0411846118 switch the rest of proc_ns_operations to working with &...->ns
    64964528b24e make proc_ns_operations work with struct ns_common * instead of void *
    6344c433a452 new helpers: ns_alloc_inum/ns_free_inum
    33c429405a2c copy address of proc_ns_ops into ns_common
    f77c80142e1a bury struct proc_ns in fs/proc
    292662014509 dcache.c: call ->d_prune() regardless of d_unhashed()
    e149ed2b805f take the targets of /proc/*/ns/* symlinks to separate fs
    
    Cherry-pick part of reverted patches back from VZ8:
    
    bcac25a58bfc kernel: add a helper to get an owning user namespace for a namespace
    6786741dbf99 nsfs: add ioctl to get an owning user namespace for ns file descriptor
    a7306ed8d94a nsfs: add ioctl to get a parent namespace
    c62cce2caee5 net: add an ioctl to get a socket network namespace
    25b14e92af1a ns: allow ns_entries to have custom symlink content
    eaa0d190bfe1 pidns: expose task pid_ns_for_children to userspace
    
    Cherry-pick reverted patches back from MS (we also need them to vz8):
    
    75509fd88fbd nsfs: Add a show_path method to fix mountinfo
    24dce0800baa net: Export open_related_ns()
    d8d211a2a0c3 net: Make extern and export get_net_ns()
    f2780d6d7475 tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of tun device
    0c3e0e3bb623 tun: Add ioctl() TUNGETDEVNETNS cmd to allow obtaining real net ns of tun device
    073c516ff735 nsfs: mark dentry with DCACHE_RCUACCESS
    
    On this kernel I've runed zdtm, so the change should not break interfaces.
    
    https://jira.sw.ru/browse/PSBM-102357
    
    Al Viro (10):
      ms: common object embedded into various struct ....ns
      make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns
      netns: switch ->get()/->put()/->install()/->inum() to working with
        &net->ns
      switch the rest of proc_ns_operations to working with &...->ns
      make proc_ns_operations work with struct ns_common * instead of void *
      new helpers: ns_alloc_inum/ns_free_inum
      copy address of proc_ns_ops into ns_common
      bury struct proc_ns in fs/proc
      dcache.c: call ->d_prune() regardless of d_unhashed()
      take the targets of /proc/*/ns/* symlinks to separate fs
    
    Andrey Vagin (4):
      kernel: add a helper to get an owning user namespace for a namespace
      nsfs: add ioctl to get an owning user namespace for ns file descriptor
      nsfs: add ioctl to get a parent namespace
      net: add an ioctl to get a socket network namespace
    
    Cong Wang (1):
      nsfs: mark dentry with DCACHE_RCUACCESS
    
    Eric W. Biederman (1):
      nsfs: Add a show_path method to fix mountinfo
    
    Kirill Tkhai (6):
      ns: allow ns_entries to have custom symlink content
      pidns: expose task pid_ns_for_children to userspace
      net: Export open_related_ns()
      net: Make extern and export get_net_ns()
      tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of tun device
      tun: Add ioctl() TUNGETDEVNETNS cmd to allow obtaining real net ns of
        tun device
    
    Pavel Tikhomirov (10):
      Revert "proc: add a proc_show_path method to fix mountinfo"
      Revert "ms/tun: Add ioctl() TUNGETDEVNETNS cmd to allow obtaining real
        net ns of tun device"
      Revert "ms/net: add an ioctl to get a socket network namespace"
      Revert "ms/tun: Add ioctl() SIOCGSKNS cmd to allow obtaining net ns of
        tun device"
      Revert "nsfs: add ioctl to get a parent namespace"
      Revert "nsfs: add ioctl to get an owning user namespace for ns file
        descriptor"
      Revert "kernel: add a helper to get an owning user namespace for a
        namespace"
      Revert "ms/pidns: expose task pid_ns_for_children to userspace"
      Revert "ms/ns: allow ns_entries to have custom symlink content"
      userns: move EXPORT_SYMBOL closer to current_in_userns
---
 drivers/net/tun.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

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diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 81b305abbf051..08332bdff1bca 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -71,6 +71,7 @@ 
 #include <net/sock.h>
 #include <linux/skb_array.h>
 #include <linux/seq_file.h>
+#include <linux/socket.h>
 
 #include <asm/uaccess.h>
 
@@ -2329,6 +2330,7 @@  static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 	void __user* argp = (void __user*)arg;
 	unsigned int ifindex, carrier;
 	struct ifreq ifr;
+	struct net *net;
 	kuid_t owner;
 	kgid_t group;
 	int sndbuf;
@@ -2338,7 +2340,7 @@  static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 	bool do_notify = false;
 
 	if (cmd == TUNSETIFF || cmd == TUNSETQUEUE || cmd == TUNSETACCTID ||
-			_IOC_TYPE(cmd) == 0x89) {
+	    (_IOC_TYPE(cmd) == 0x89 && cmd != SIOCGSKNS)) {
 		if (copy_from_user(&ifr, argp, ifreq_len))
 			return -EFAULT;
 	} else {
@@ -2365,7 +2367,11 @@  static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 #endif /* CONFIG_VE_TUNTAP_ACCOUNTING */
 
 	tun = __tun_get(tfile);
-	if (cmd == TUNSETIFF && !tun) {
+	net = sock_net(&tfile->sk);
+	if (cmd == TUNSETIFF) {
+		ret = -EEXIST;
+		if (tun)
+			goto unlock;
 		ifr.ifr_name[IFNAMSIZ-1] = '\0';
 
 		ret = tun_set_iff(tfile->net, file, &ifr);
@@ -2390,6 +2396,14 @@  static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 		tfile->ifindex = ifindex;
 		goto unlock;
 	}
+	if (cmd == SIOCGSKNS) {
+		ret = -EPERM;
+		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+			goto unlock;
+
+		ret = open_related_ns(&net->ns, get_net_ns);
+		goto unlock;
+	}
 
 	ret = -EBADFD;
 	if (!tun)