Subject: Re: [BUG] unable to handle kernel NULL pointer dereference
From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Date: Sun, 16 Feb 2014 12:27:33 -0500
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>
In-reply-to: <20140215232508.GB4508@xxxxxxx>
Organization: PrimaryData Inc
References:
<1392466251.41282.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
<1392494917.71728.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
<20140215203015.GA4528@xxxxxxx>
<1392498262.98385.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
<20140215232508.GB4508@xxxxxxx>
Please ensure that you post to the linux-nfs@xxxxxxxxxxxxxxx when
reporting NFS and RPC related bugs.
On Sun, 2014-02-16 at 00:25 +0100, Borislav Petkov wrote:
> On Sat, Feb 15, 2014 at 01:04:22PM -0800, John wrote:
> > Thanks for the reply, Boris. The .config is unmodified
> > from the Arch Distro default for 3.13.3-1 which can be found
> > here: http://pastebin.com/LPGZ8ZqA
>
> Yep, it is that struct net *net argument to put_pipe_version() which is NULL:
>
> 12: 55 push %ebp
> 13: 89 e5 mov %esp,%ebp
> 15: 56 push %esi
> 16: 53 push %ebx
> 17: 3e 8d 74 26 00 lea %ds:0x0(%esi,%eiz,1),%esi
> 1c: 8b 1d 28 e9 a3 f8 mov 0xf8a3e928,%ebx
> 22: 89 c6 mov %eax,%esi
> 24: e8 59 64 5f c8 call 0xc85f6482
> 29: 85 db test %ebx,%ebx
> 2b:* 8b 86 58 08 00 00 mov 0x858(%esi),%eax <-- trapping instruction
>
> put_pipe_version:
> pushl %ebp #
> movl %esp, %ebp #,
> pushl %esi #
> pushl %ebx #
> call mcount
> movl sunrpc_net_id, %ebx # sunrpc_net_id, sunrpc_net_id.130
> movl %eax, %esi # net, net
> call __rcu_read_lock #
> testl %ebx, %ebx # sunrpc_net_id.130
> movl 2136(%esi), %eax # MEM[(struct net_generic * const *)net_4(D) + 2136B], ng <-- trapping insn
>
>
> [ 137.689996] ESI: 00000000 EDI: f56efc00 EBP: f568fee8 ESP: f568fee0
> ^^^^^^^^
>
> Here's the c/asm interleaved version:
>
> static void put_pipe_version(struct net *net)
> {
> d80: 55 push %ebp
> d81: 89 e5 mov %esp,%ebp
> d83: 56 push %esi
> d84: 53 push %ebx
> d85: e8 fc ff ff ff call d86 <put_pipe_version+0x6>
> d86: R_386_PC32 mcount
> struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
> d8a: 8b 1d 00 00 00 00 mov 0x0,%ebx
> d8c: R_386_32 sunrpc_net_id
> spin_unlock(&pipe_version_lock);
> return ret;
> }
>
> static void put_pipe_version(struct net *net)
> {
> d90: 89 c6 mov %eax,%esi
> * block, but only when acquiring spinlocks that are subject to priority
> * inheritance.
> */
> static inline void rcu_read_lock(void)
> {
> __rcu_read_lock();
> d92: e8 fc ff ff ff call d93 <put_pipe_version+0x13>
> d93: R_386_PC32 __rcu_read_lock
> struct net_generic *ng;
> void *ptr;
>
> rcu_read_lock();
> ng = rcu_dereference(net->gen);
> BUG_ON(id == 0 || id > ng->len);
> d97: 85 db test %ebx,%ebx
> {
> struct net_generic *ng;
> void *ptr;
>
> rcu_read_lock();
> ng = rcu_dereference(net->gen);
> d99: 8b 86 58 08 00 00 mov 0x858(%esi),%eax <-- trapping insn
>
>
> I guess you could avoid the crash if you did
>
> if (!net)
> return;
>
> in put_pipe_version() but this hardly is the right solution. Someone
> else has to make sense of this thing, not me. :-)
Does the following patch help?
Works for me on 3.14-rc3.
Feel free to add my
Tested-by: Dieter Nützel <Dieter@xxxxxxxxxxxxx>
Thanks,
Dieter
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
--
1.8.5.3
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
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