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    Subject[PATCH 173/241] netlink: add reference of module in netlink_dump_start
    Date
    3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Gao feng <gaofeng@cn.fujitsu.com>

    commit 6dc878a8ca39e93f70c42f3dd7260bde10c1e0f1 upstream.

    I get a panic when I use ss -a and rmmod inet_diag at the
    same time.

    It's because netlink_dump uses inet_diag_dump which belongs to module
    inet_diag.

    I search the codes and find many modules have the same problem. We
    need to add a reference to the module which the cb->dump belongs to.

    Thanks for all help from Stephen,Jan,Eric,Steffen and Pablo.

    Change From v3:
    change netlink_dump_start to inline,suggestion from Pablo and
    Eric.

    Change From v2:
    delete netlink_dump_done,and call module_put in netlink_dump
    and netlink_sock_destruct.

    Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    include/linux/netlink.h | 21 +++++++++++++++++----
    net/netlink/af_netlink.c | 29 +++++++++++++++++++++--------
    2 files changed, 38 insertions(+), 12 deletions(-)

    diff --git a/include/linux/netlink.h b/include/linux/netlink.h
    index 0f628ff..6f393c2 100644
    --- a/include/linux/netlink.h
    +++ b/include/linux/netlink.h
    @@ -153,6 +153,7 @@ struct nlattr {

    #include <linux/capability.h>
    #include <linux/skbuff.h>
    +#include <linux/export.h>

    struct net;

    @@ -226,6 +227,8 @@ struct netlink_callback {
    struct netlink_callback *cb);
    int (*done)(struct netlink_callback *cb);
    void *data;
    + /* the module that dump function belong to */
    + struct module *module;
    u16 family;
    u16 min_dump_alloc;
    unsigned int prev_seq, seq;
    @@ -251,14 +254,24 @@ __nlmsg_put(struct sk_buff *skb, u32 pid, u32 seq, int type, int len, int flags)

    struct netlink_dump_control {
    int (*dump)(struct sk_buff *skb, struct netlink_callback *);
    - int (*done)(struct netlink_callback*);
    + int (*done)(struct netlink_callback *);
    void *data;
    + struct module *module;
    u16 min_dump_alloc;
    };

    -extern int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    - const struct nlmsghdr *nlh,
    - struct netlink_dump_control *control);
    +extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    + const struct nlmsghdr *nlh,
    + struct netlink_dump_control *control);
    +static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    + const struct nlmsghdr *nlh,
    + struct netlink_dump_control *control)
    +{
    + if (!control->module)
    + control->module = THIS_MODULE;
    +
    + return __netlink_dump_start(ssk, skb, nlh, control);
    +}


    #define NL_NONROOT_RECV 0x1
    diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
    index 20b32fd..efffdfc 100644
    --- a/net/netlink/af_netlink.c
    +++ b/net/netlink/af_netlink.c
    @@ -167,6 +167,8 @@ static void netlink_sock_destruct(struct sock *sk)
    if (nlk->cb) {
    if (nlk->cb->done)
    nlk->cb->done(nlk->cb);
    +
    + module_put(nlk->cb->module);
    netlink_destroy_callback(nlk->cb);
    }

    @@ -1737,6 +1739,7 @@ static int netlink_dump(struct sock *sk)
    nlk->cb = NULL;
    mutex_unlock(nlk->cb_mutex);

    + module_put(cb->module);
    netlink_consume_callback(cb);
    return 0;

    @@ -1746,9 +1749,9 @@ errout_skb:
    return err;
    }

    -int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    - const struct nlmsghdr *nlh,
    - struct netlink_dump_control *control)
    +int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    + const struct nlmsghdr *nlh,
    + struct netlink_dump_control *control)
    {
    struct netlink_callback *cb;
    struct sock *sk;
    @@ -1763,6 +1766,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    cb->done = control->done;
    cb->nlh = nlh;
    cb->data = control->data;
    + cb->module = control->module;
    cb->min_dump_alloc = control->min_dump_alloc;
    atomic_inc(&skb->users);
    cb->skb = skb;
    @@ -1773,19 +1777,28 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    return -ECONNREFUSED;
    }
    nlk = nlk_sk(sk);
    - /* A dump is in progress... */
    +
    mutex_lock(nlk->cb_mutex);
    + /* A dump is in progress... */
    if (nlk->cb) {
    mutex_unlock(nlk->cb_mutex);
    netlink_destroy_callback(cb);
    - sock_put(sk);
    - return -EBUSY;
    + ret = -EBUSY;
    + goto out;
    }
    + /* add reference of module which cb->dump belongs to */
    + if (!try_module_get(cb->module)) {
    + mutex_unlock(nlk->cb_mutex);
    + netlink_destroy_callback(cb);
    + ret = -EPROTONOSUPPORT;
    + goto out;
    + }
    +
    nlk->cb = cb;
    mutex_unlock(nlk->cb_mutex);

    ret = netlink_dump(sk);
    -
    +out:
    sock_put(sk);

    if (ret)
    @@ -1796,7 +1809,7 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
    */
    return -EINTR;
    }
    -EXPORT_SYMBOL(netlink_dump_start);
    +EXPORT_SYMBOL(__netlink_dump_start);

    void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
    {
    --
    1.7.9.5


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