Re: [BUG] unable to handle kernel NULL pointer dereference

[John]

----- Original Message -----
> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> To: Borislav Petkov <bp@xxxxxxxxx>; Linux NFS Mailing List <linux-nfs@xxxxxxxxxxxxxxx>
> Cc: John <da_audiophile@xxxxxxxxx>; lkml <linux-kernel@xxxxxxxxxxxxxxx>; "netdev@xxxxxxxxxxxxxxx" <netdev@xxxxxxxxxxxxxxx>; "stephen@xxxxxxxxxxxxxxxxxx" <stephen@xxxxxxxxxxxxxxxxxx>; "mlindner@xxxxxxxxxxx" <mlindner@xxxxxxxxxxx>; J. Bruce Fields <bfields@xxxxxxxxxxxx>
> Sent: Sunday, February 16, 2014 12:27 PM
> Subject: Re: [BUG] unable to handle kernel NULL pointer dereference
> 
> Please ensure that you post to the linux-nfs@xxxxxxxxxxxxxxx when
> reporting NFS and RPC related bugs.
> 
> Does the following patch help?
> 
> 8<-------------------------------------------------------------------
> From 0e57b109cd7b17d6e6f16c3454427372a583b18a Mon Sep 17 00:00:00 2001
> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> Date: Sun, 16 Feb 2014 12:14:13 -0500
> Subject: [PATCH] SUNRPC: Ensure that gss_auth isn't freed before its upcall
> messages
> 
> Fix a race in which the RPC client is shutting down while the
> gss daemon is processing a downcall. If the RPC client manages to
> shut down before the gss daemon is done, then the struct gss_auth
> used in gss_release_msg() may have already been freed.
> 
> Link: 
> http://lkml.kernel.org/r/1392494917.71728.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Reported-by: John <da_audiophile@xxxxxxxxx>
> Reported-by: Borislav Petkov <bp@xxxxxxxxx>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> net/sunrpc/auth_gss/auth_gss.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
> index 44a61e8fda6f..1ba1fd114912 100644
> --- a/net/sunrpc/auth_gss/auth_gss.c
> +++ b/net/sunrpc/auth_gss/auth_gss.c
> @@ -108,6 +108,7 @@ struct gss_auth {
> static DEFINE_SPINLOCK(pipe_version_lock);
> static struct rpc_wait_queue pipe_version_rpc_waitqueue;
> static DECLARE_WAIT_QUEUE_HEAD(pipe_version_waitqueue);
> +static void gss_put_auth(struct gss_auth *gss_auth);
> 
> static void gss_free_ctx(struct gss_cl_ctx *);
> static const struct rpc_pipe_ops gss_upcall_ops_v0;
> @@ -320,6 +321,7 @@ gss_release_msg(struct gss_upcall_msg *gss_msg)
>     if (gss_msg->ctx != NULL)
>         gss_put_ctx(gss_msg->ctx);
>     rpc_destroy_wait_queue(&gss_msg->rpc_waitqueue);
> +    gss_put_auth(gss_msg->auth);
>     kfree(gss_msg);
> }
> 
> @@ -500,6 +502,7 @@ gss_alloc_msg(struct gss_auth *gss_auth,
>         if (err)
>             goto err_free_msg;
>     };
> +    kref_get(&gss_auth->kref);
>     return gss_msg;
> err_free_msg:
>     kfree(gss_msg);
> @@ -1064,6 +1067,12 @@ gss_free_callback(struct kref *kref)
> }
> 
> static void
> +gss_put_auth(struct gss_auth *gss_auth)
> +{
> +    kref_put(&gss_auth->kref, gss_free_callback);
> +}
> +
> +static void
> gss_destroy(struct rpc_auth *auth)
> {
>     struct gss_auth *gss_auth = container_of(auth,
> @@ -1084,7 +1093,7 @@ gss_destroy(struct rpc_auth *auth)
>     gss_auth->gss_pipe[1] = NULL;
>     rpcauth_destroy_credcache(auth);
> 
> -    kref_put(&gss_auth->kref, gss_free_callback);
> +    gss_put_auth(gss_auth);
> }
> 
> /*
> @@ -1255,7 +1264,7 @@ gss_destroy_nullcred(struct rpc_cred *cred)
>     call_rcu(&cred->cr_rcu, gss_free_cred_callback);
>     if (ctx)
>         gss_put_ctx(ctx);
> -    kref_put(&gss_auth->kref, gss_free_callback);
> +    gss_put_auth(gss_auth);
> 
> }
> 
> static void
> -- 


Tested-by: John <da_audiophile@xxxxxxxxx>


Fixes the problem on 3.13.3 for me (i686). Thank you.
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