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SubjectRe: [PATCH] xfrm6_tunnel: Fix potential panic when unloading xfrm6_tunnel module
On Thu, Mar 14, 2019 at 02:59:42PM +0800, Su Yanjun wrote:
> When unloading xfrm6_tunnel module, xfrm6_tunnel_fini directly
> frees the xfrm6_tunnel_spi_kmem. Maybe someone has gotten the
> xfrm6_tunnel_spi, so need to wait it.
>
> Fixes: 91cc3bb0b04ff("xfrm6_tunnel: RCU conversion")
> Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
> ---
> net/ipv6/xfrm6_tunnel.c | 4 ++++
> 1 file changed, 4 insertions(+)

This looks good to me. And it's not just the matter of accessing
freed memory. A worse problem would be trying to execute code
from an unloaded module.

Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

> diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
> index bc65db7..12cb3aa 100644
> --- a/net/ipv6/xfrm6_tunnel.c
> +++ b/net/ipv6/xfrm6_tunnel.c
> @@ -402,6 +402,10 @@ static void __exit xfrm6_tunnel_fini(void)
> xfrm6_tunnel_deregister(&xfrm6_tunnel_handler, AF_INET6);
> xfrm_unregister_type(&xfrm6_tunnel_type, AF_INET6);
> unregister_pernet_subsys(&xfrm6_tunnel_net_ops);
> + /* Someone maybe has gotten the xfrm6_tunnel_spi.
> + * So need to wait it.
> + */
> + rcu_barrier();
> kmem_cache_destroy(xfrm6_tunnel_spi_kmem);
> }

Thanks,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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