Messages in this thread Patches in this message | | | From | "Zhang, Qiang" <> | Subject | 回复: [PATCH v2] tipc: Don't using smp proces sor id() in preemptible code | Date | Wed, 15 Jul 2020 05:27:04 +0000 |
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________________________________________ 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
>-----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
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