Re: [PATCH] inet_diag: fix panic when unload inet_diag
From: Eric Dumazet <hidden>
Date: 2012-09-25 06:36:57
On Tue, 2012-09-25 at 10:48 +0800, Gao feng wrote:
when inet_diag being compiled as module, inet_diag_handler_dump set netlink_dump_control.dump to inet_diag_dump,so if module inet_diag is unloaded,netlink will still try to call this function in netlink_dump. this will cause kernel panic. fix this by adding a reference of inet_diag module before setting netlink_callback, and release this reference in netlink_callback.done. Thanks for all help from Stephen,Jan and Eric.
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quoted hunk ↗ jump to hunk
@@ -1001,8 +1025,26 @@ static int inet_diag_handler_dump(struct sk_buff *skb, struct nlmsghdr *h) { struct netlink_dump_control c = { .dump = inet_diag_dump, + .done = inet_diag_done, }; - return netlink_dump_start(net->diag_nlsk, skb, h, &c); + int err; + /* + * netlink_dump will call inet_diag_dump, + * so we need a reference of THIS_MODULE. + */ + if (!try_module_get(THIS_MODULE)) + return -EPROTONOSUPPORT; + + err = netlink_dump_start(net->diag_nlsk, skb, h, &c); + + if ((err != -EINTR) && (err != -ENOBUFS)) { + /* + * netlink_callback set failed, release the + * referenct of THIS_MODULE. + */ + module_put(THIS_MODULE); + } + return err; } }
Hmm... this seems error prone... In the future, netlink_dump_start() could be changed to return other errors than EINTR or ENOBUFS that need the module_put() I would change netlink_dump_start() to __netlink_dump_start() and add a module param to it, so that this module stuff is centralized in __netlink_dump_start() Then, instead of calling (from inet_diag) netlink_dump_start(net->diag_nlsk, skb, nlh, &c); you would use : __netlink_dump_start(net->diag_nlsk, skb, nlh, &c, THIS_MODULE); I wonder if this fix is not needed elsewhere eventually (net/unix/af_unix.c for example ?)