________________________________________
发件人: Tuong Tong Lien <tuong.t.l...@dektech.com.au>
发送时间: 2020年7月15日 11:53
收件人: Zhang, Qiang; Eric Dumazet; jma...@redhat.com; da...@davemloft.net;
k...@kernel.org; Xue, Ying
抄送: net...@vger.kernel.org; tipc-discuss...@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.zh...@windriver.com>
> Sent: Wednesday, July 15, 2020 9:13 AM
> To: Eric Dumazet <eric.duma...@gmail.com>; jma...@redhat.com;
> da...@davemloft.net; k...@kernel.org; Tuong Tong Lien
> <tuong.t.l...@dektech.com.au>; Xue, Ying <ying....@windriver.com>
> Cc: net...@vger.kernel.org; tipc-discuss...@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.duma...@gmail.com>
> 发送时间: 2020年7月14日 22:15
> 收件人: Zhang, Qiang; jma...@redhat.com; da...@davemloft.net; k...@kernel.org;
> tuong.t.l...@dektech.com.au;
> eric.duma...@gmail.com; Xue, Ying
> 抄送: net...@vger.kernel.org; tipc-discuss...@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.zh...@windriver.com wrote:
> > From: Zhang Qiang <qiang.zh...@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+263f8c0d007dc09b2...@syzkaller.appspotmail.com
> > Signed-off-by: Zhang Qiang <qiang.zh...@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
>-----Original Message-----
>From: Tuong Tong Lien <tuong.t.l...@dektech.com.au>
>Sent: Friday, July 10, 2020 5:11 PM
>To: jma...@redhat.com; ma...@donjonn.com; ying....@windriver.com;
>tipc-discuss...@lists.sourceforge.net
>Cc: tipc-dek <tipc-...@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.l...@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
