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    Subject[PATCH 5.12 054/178] net: make get_net_ns return error if NET_NS is disabled
    Date
    From: Changbin Du <changbin.du@gmail.com>

    [ Upstream commit ea6932d70e223e02fea3ae20a4feff05d7c1ea9a ]

    There is a panic in socket ioctl cmd SIOCGSKNS when NET_NS is not enabled.
    The reason is that nsfs tries to access ns->ops but the proc_ns_operations
    is not implemented in this case.

    [7.670023] Unable to handle kernel NULL pointer dereference at virtual address 00000010
    [7.670268] pgd = 32b54000
    [7.670544] [00000010] *pgd=00000000
    [7.671861] Internal error: Oops: 5 [#1] SMP ARM
    [7.672315] Modules linked in:
    [7.672918] CPU: 0 PID: 1 Comm: systemd Not tainted 5.13.0-rc3-00375-g6799d4f2da49 #16
    [7.673309] Hardware name: Generic DT based system
    [7.673642] PC is at nsfs_evict+0x24/0x30
    [7.674486] LR is at clear_inode+0x20/0x9c

    The same to tun SIOCGSKNS command.

    To fix this problem, we make get_net_ns() return -EINVAL when NET_NS is
    disabled. Meanwhile move it to right place net/core/net_namespace.c.

    Signed-off-by: Changbin Du <changbin.du@gmail.com>
    Fixes: c62cce2caee5 ("net: add an ioctl to get a socket network namespace")
    Cc: Cong Wang <xiyou.wangcong@gmail.com>
    Cc: Jakub Kicinski <kuba@kernel.org>
    Cc: David Laight <David.Laight@ACULAB.COM>
    Cc: Christian Brauner <christian.brauner@ubuntu.com>
    Suggested-by: Jakub Kicinski <kuba@kernel.org>
    Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/socket.h | 2 --
    include/net/net_namespace.h | 7 +++++++
    net/core/net_namespace.c | 12 ++++++++++++
    net/socket.c | 13 -------------
    4 files changed, 19 insertions(+), 15 deletions(-)

    diff --git a/include/linux/socket.h b/include/linux/socket.h
    index 385894b4a8bb..42222a84167f 100644
    --- a/include/linux/socket.h
    +++ b/include/linux/socket.h
    @@ -438,6 +438,4 @@ extern int __sys_socketpair(int family, int type, int protocol,
    int __user *usockvec);
    extern int __sys_shutdown_sock(struct socket *sock, int how);
    extern int __sys_shutdown(int fd, int how);
    -
    -extern struct ns_common *get_net_ns(struct ns_common *ns);
    #endif /* _LINUX_SOCKET_H */
    diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
    index dcaee24a4d87..14b6f7f44532 100644
    --- a/include/net/net_namespace.h
    +++ b/include/net/net_namespace.h
    @@ -197,6 +197,8 @@ struct net *copy_net_ns(unsigned long flags, struct user_namespace *user_ns,
    void net_ns_get_ownership(const struct net *net, kuid_t *uid, kgid_t *gid);

    void net_ns_barrier(void);
    +
    +struct ns_common *get_net_ns(struct ns_common *ns);
    #else /* CONFIG_NET_NS */
    #include <linux/sched.h>
    #include <linux/nsproxy.h>
    @@ -216,6 +218,11 @@ static inline void net_ns_get_ownership(const struct net *net,
    }

    static inline void net_ns_barrier(void) {}
    +
    +static inline struct ns_common *get_net_ns(struct ns_common *ns)
    +{
    + return ERR_PTR(-EINVAL);
    +}
    #endif /* CONFIG_NET_NS */


    diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
    index 43b6ac4c4439..cc8dafb25d61 100644
    --- a/net/core/net_namespace.c
    +++ b/net/core/net_namespace.c
    @@ -641,6 +641,18 @@ void __put_net(struct net *net)
    }
    EXPORT_SYMBOL_GPL(__put_net);

    +/**
    + * get_net_ns - increment the refcount of the network namespace
    + * @ns: common namespace (net)
    + *
    + * Returns the net's common namespace.
    + */
    +struct ns_common *get_net_ns(struct ns_common *ns)
    +{
    + return &get_net(container_of(ns, struct net, ns))->ns;
    +}
    +EXPORT_SYMBOL_GPL(get_net_ns);
    +
    struct net *get_net_ns_by_fd(int fd)
    {
    struct file *file;
    diff --git a/net/socket.c b/net/socket.c
    index 84a8049c2b09..03259cb919f7 100644
    --- a/net/socket.c
    +++ b/net/socket.c
    @@ -1072,19 +1072,6 @@ static long sock_do_ioctl(struct net *net, struct socket *sock,
    * what to do with it - that's up to the protocol still.
    */

    -/**
    - * get_net_ns - increment the refcount of the network namespace
    - * @ns: common namespace (net)
    - *
    - * Returns the net's common namespace.
    - */
    -
    -struct ns_common *get_net_ns(struct ns_common *ns)
    -{
    - return &get_net(container_of(ns, struct net, ns))->ns;
    -}
    -EXPORT_SYMBOL_GPL(get_net_ns);
    -
    static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
    {
    struct socket *sock;
    --
    2.30.2


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