ad9852af97
The helper module would be unloaded after nf_conntrack_helper_unregister,
so it may cause a possible panic caused by race.
nf_ct_iterate_destroy(unhelp, me) reset the helper of conntrack as NULL,
but maybe someone has gotten the helper pointer during this period. Then
it would panic, when it accesses the helper and the module was unloaded.
Take an example as following:
CPU0 CPU1
ctnetlink_dump_helpinfo
helper = rcu_dereference(help->helper);
unhelp
set helper as NULL
unload helper module
helper->to_nlattr(skb, ct);
As above, the cpu0 tries to access the helper and its module is unloaded,
then the panic happens.
Signed-off-by: Gao Feng <gfree.wind@vip.163.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.