lkml.org 
[lkml]   [2020]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patches in this message
/
From
Subject回复: [PATCH v2] tipc: Don't using smp proces sor id() in preemptible code
Date


________________________________________
发件人: Zhang, Qiang <Qiang.Zhang@windriver.com>
发送时间: 2020年7月15日 13:27
收件人: Tuong Tong Lien; Eric Dumazet; jmaloy@redhat.com; davem@davemloft.net; kuba@kernel.org; Xue, Ying
抄送: netdev@vger.kernel.org; tipc-discussion@lists.sourceforge.net; linux-kernel@vger.kernel.org
主题: 回复: [PATCH v2] tipc: Don't using smp_processor_id() in preemptible code



________________________________________
发件人: Tuong Tong Lien <tuong.t.lien@dektech.com.au>
发送时间: 2020年7月15日 11:53
收件人: Zhang, Qiang; Eric Dumazet; jmaloy@redhat.com; davem@davemloft.net; kuba@kernel.org; Xue, Ying
抄送: netdev@vger.kernel.org; tipc-discussion@lists.sourceforge.net; linux-kernel@vger.kernel.org
主题: RE: [PATCH v2] tipc: Don't using smp_processor_id() in preemptible code



> -----Original Message-----
> From: Zhang, Qiang <Qiang.Zhang@windriver.com>
> Sent: Wednesday, July 15, 2020 9:13 AM
> To: Eric Dumazet <eric.dumazet@gmail.com>; jmaloy@redhat.com; davem@davemloft.net; kuba@kernel.org; Tuong Tong Lien
> <tuong.t.lien@dektech.com.au>; Xue, Ying <Ying.Xue@windriver.com>
> Cc: netdev@vger.kernel.org; tipc-discussion@lists.sourceforge.net; linux-kernel@vger.kernel.org
> Subject: 回复: [PATCH v2] tipc: Don't using smp_processor_id() in preemptible code
>
>
>
> ________________________________________
> 发件人: Eric Dumazet <eric.dumazet@gmail.com>
> 发送时间: 2020年7月14日 22:15
> 收件人: Zhang, Qiang; jmaloy@redhat.com; davem@davemloft.net; kuba@kernel.org; tuong.t.lien@dektech.com.au;
> eric.dumazet@gmail.com; Xue, Ying
> 抄送: netdev@vger.kernel.org; tipc-discussion@lists.sourceforge.net; linux-kernel@vger.kernel.org
> 主题: Re: [PATCH v2] tipc: Don't using smp_processor_id() in preemptible code
>
>
>
> On 7/14/20 1:05 AM, qiang.zhang@windriver.com wrote:
> > From: Zhang Qiang <qiang.zhang@windriver.com>
> >
> > CPU: 0 PID: 6801 Comm: syz-executor201 Not tainted 5.8.0-rc4-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine,
> > BIOS Google 01/01/2011
> >
> > Fixes: fc1b6d6de2208 ("tipc: introduce TIPC encryption & authentication")
> > Reported-by: syzbot+263f8c0d007dc09b2dda@syzkaller.appspotmail.com
> > Signed-off-by: Zhang Qiang <qiang.zhang@windriver.com>
> > ---
> > v1->v2:
> > add fixes tags.
> >
> > net/tipc/crypto.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> > index 8c47ded2edb6..520af0afe1b3 100644
> > --- a/net/tipc/crypto.c
> > +++ b/net/tipc/crypto.c
> > @@ -399,9 +399,10 @@ static void tipc_aead_users_set(struct tipc_aead __rcu *aead, int val)
> > */
> > static struct crypto_aead *tipc_aead_tfm_next(struct tipc_aead *aead)
> > {
> > - struct tipc_tfm **tfm_entry = this_cpu_ptr(aead->tfm_entry);
> > + struct tipc_tfm **tfm_entry = get_cpu_ptr(aead->tfm_entry);
> >
> > *tfm_entry = list_next_entry(*tfm_entry, list);
> > + put_cpu_ptr(tfm_entry);
> > return (*tfm_entry)->tfm;
> > }
> >
> >
>
> > You have not explained why this was safe.
> >
> > This seems to hide a real bug.
> >
> > Presumably callers of this function should have disable preemption, and maybe > interrupts as well.
> >
> >Right after put_cpu_ptr(tfm_entry), this thread could migrate to another cpu, >and still access
> >data owned by the old cpu.
>
> Thanks for you suggest, I will check code again.
>

>Actually, last week I sent a similar patch to tipc-discussion which covers the
>case as well (there is also another place causing the same issue...). If you
>don't mind, you can take a look at below (just copied/pasted).

>BR/Tuong


>Hi Tuong Tong Lien

>The tipc_aead_free is RCU callback, this func is called in softirq context which
>preemption has been banned
>so should not add preempt_disable/enable.

>thanks
>Zhang Qiang
sorry there are some questions in my reply. the tipc_aead_free function may also be called in the thread context. if enable CONFIG_RCU_BOOST

>-----Original Message-----
>From: Tuong Tong Lien <tuong.t.lien@dektech.com.au>
>Sent: Friday, July 10, 2020 5:11 PM
>To: jmaloy@redhat.com; maloy@donjonn.com; ying.xue@windriver.com; tipc-discussion@lists.sourceforge.net
>Cc: tipc-dek <tipc-dek@dektech.com.au>
Subject: [PATCH RFC 1/5] tipc: fix using smp_processor_id() in preemptible
>
>The 'this_cpu_ptr()' is used to obtain the AEAD key' TFM on the current
CPU for encryption, however the execution can be preemptible since it's
actually user-space context, so the 'using smp_processor_id() in
preemptible' has been observed.

We fix the issue by using the 'get/put_cpu_ptr()' API which consists of
a 'preempt_disable()' instead.

Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
---
net/tipc/crypto.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index c8c47fc72653..1827ce4fac5d 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -326,7 +326,8 @@ static void tipc_aead_free(struct rcu_head *rp)
if (aead->cloned) {
tipc_aead_put(aead->cloned);
} else {
- head = *this_cpu_ptr(aead->tfm_entry);
+ head = *get_cpu_ptr(aead->tfm_entry);
+ put_cpu_ptr(aead->tfm_entry);
list_for_each_entry_safe(tfm_entry, tmp, &head->list, list) {
crypto_free_aead(tfm_entry->tfm);
list_del(&tfm_entry->list);
@@ -399,10 +400,15 @@ static void tipc_aead_users_set(struct tipc_aead __rcu *aead, int val)
*/
static struct crypto_aead *tipc_aead_tfm_next(struct tipc_aead *aead)
{
- struct tipc_tfm **tfm_entry = this_cpu_ptr(aead->tfm_entry);
+ struct tipc_tfm **tfm_entry;
+ struct crypto_aead *tfm;

+ tfm_entry = get_cpu_ptr(aead->tfm_entry);
*tfm_entry = list_next_entry(*tfm_entry, list);
- return (*tfm_entry)->tfm;
+ tfm = (*tfm_entry)->tfm;
+ put_cpu_ptr(tfm_entry);
+
+ return tfm;
}

/**
--
2.13.7
\
 
 \ /
  Last update: 2020-07-15 08:07    [W:0.065 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site