[PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[George Kennedy]

The dev pointer can be NULL in dev_hard_header(). Add check for dev being
NULL in dev_hard_header() to avoid GPF.

general protection fault, probably for non-canonical address
    0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
Workqueue: mld mld_ifc_work
RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
    (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
    knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
Call Trace:
 <TASK>
neigh_connected_output (./include/linux/netdevice.h:3060
    net/core/neighbour.c:1595)
ip6_finish_output2 (./include/net/neighbour.h:546
    net/ipv6/ip6_output.c:134)
ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
NF_HOOK.constprop.0 (./include/net/dst.h:445
    ./include/linux/netfilter.h:302)
mld_sendpack (net/ipv6/mcast.c:1824)
mld_send_cr (net/ipv6/mcast.c:2122)
mld_ifc_work (net/ipv6/mcast.c:2655)
process_one_work (kernel/workqueue.c:2294)
worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
kthread (kernel/kthread.c:376)
ret_from_fork (arch/x86/entry/entry_64.S:312)
 </TASK>
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace 0000000000000000 ]---

Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: George Kennedy <george.kennedy@oracle.com>
---
 include/linux/netdevice.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index eddf8ee270e7..9b25a6301fa5 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
 				  const void *daddr, const void *saddr,
 				  unsigned int len)
 {
-	if (!dev->header_ops || !dev->header_ops->create)
+	if (!dev || !dev->header_ops || !dev->header_ops->create)
 		return 0;
 
 	return dev->header_ops->create(skb, dev, type, daddr, saddr, len);
-- 
2.31.1

Re: [PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[Pavan Chebbi]

[-- Attachment #1: Type: text/plain, Size: 3274 bytes --]

On Wed, Nov 30, 2022 at 7:43 PM George Kennedy
<george.kennedy@oracle.com> wrote:
>
> The dev pointer can be NULL in dev_hard_header(). Add check for dev being
> NULL in dev_hard_header() to avoid GPF.
>
> general protection fault, probably for non-canonical address
>     0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
> KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
> CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
> Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
> Workqueue: mld mld_ifc_work
> RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
>     (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
> RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
> RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
> RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
> RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
> R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
> FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
>     knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
> Call Trace:
>  <TASK>
> neigh_connected_output (./include/linux/netdevice.h:3060
>     net/core/neighbour.c:1595)
> ip6_finish_output2 (./include/net/neighbour.h:546
>     net/ipv6/ip6_output.c:134)
> ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
> ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
> NF_HOOK.constprop.0 (./include/net/dst.h:445
>     ./include/linux/netfilter.h:302)
> mld_sendpack (net/ipv6/mcast.c:1824)
> mld_send_cr (net/ipv6/mcast.c:2122)
> mld_ifc_work (net/ipv6/mcast.c:2655)
> process_one_work (kernel/workqueue.c:2294)
> worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
> kthread (kernel/kthread.c:376)
> ret_from_fork (arch/x86/entry/entry_64.S:312)
>  </TASK>
> Modules linked in:
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> ---[ end trace 0000000000000000 ]---
>
> Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: George Kennedy <george.kennedy@oracle.com>
> ---
>  include/linux/netdevice.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index eddf8ee270e7..9b25a6301fa5 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
>                                   const void *daddr, const void *saddr,
>                                   unsigned int len)
>  {
> -       if (!dev->header_ops || !dev->header_ops->create)
> +       if (!dev || !dev->header_ops || !dev->header_ops->create)
>                 return 0;

net_device being NULL during eth header construction? seems like a
more serious issue?
If it indeed is a genuine scenario I think a better description is needed...

>
>         return dev->header_ops->create(skb, dev, type, daddr, saddr, len);
> --
> 2.31.1
>

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Re: [PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[Eric Dumazet]

On Thu, Dec 1, 2022 at 2:16 PM Pavan Chebbi <pavan.chebbi@broadcom.com> wrote:
>
> On Wed, Nov 30, 2022 at 7:43 PM George Kennedy
> <george.kennedy@oracle.com> wrote:
> >
> > The dev pointer can be NULL in dev_hard_header(). Add check for dev being
> > NULL in dev_hard_header() to avoid GPF.
> >
> > general protection fault, probably for non-canonical address
> >     0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
> > KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
> > CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
> > Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
> > Workqueue: mld mld_ifc_work
> > RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
> >     (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
> > RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
> > RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
> > RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
> > RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
> > R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
> > R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
> > FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
> >     knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
> > Call Trace:
> >  <TASK>
> > neigh_connected_output (./include/linux/netdevice.h:3060
> >     net/core/neighbour.c:1595)
> > ip6_finish_output2 (./include/net/neighbour.h:546
> >     net/ipv6/ip6_output.c:134)
> > ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
> > ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
> > NF_HOOK.constprop.0 (./include/net/dst.h:445
> >     ./include/linux/netfilter.h:302)
> > mld_sendpack (net/ipv6/mcast.c:1824)
> > mld_send_cr (net/ipv6/mcast.c:2122)
> > mld_ifc_work (net/ipv6/mcast.c:2655)
> > process_one_work (kernel/workqueue.c:2294)
> > worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
> > kthread (kernel/kthread.c:376)
> > ret_from_fork (arch/x86/entry/entry_64.S:312)
> >  </TASK>
> > Modules linked in:
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > ---[ end trace 0000000000000000 ]---
> >
> > Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
> > Reported-by: syzkaller <syzkaller@googlegroups.com>
> > Signed-off-by: George Kennedy <george.kennedy@oracle.com>
> > ---
> >  include/linux/netdevice.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index eddf8ee270e7..9b25a6301fa5 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
> >                                   const void *daddr, const void *saddr,
> >                                   unsigned int len)
> >  {
> > -       if (!dev->header_ops || !dev->header_ops->create)
> > +       if (!dev || !dev->header_ops || !dev->header_ops->create)

Do  you have a repro ?

This patch will not prevent a crash later I think.

Please fix the root cause, thanks !

> >                 return 0;
>
> net_device being NULL during eth header construction? seems like a
> more serious issue?
> If it indeed is a genuine scenario I think a better description is needed...
>
> >
> >         return dev->header_ops->create(skb, dev, type, daddr, saddr, len);
> > --
> > 2.31.1
> >

Re: [PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[Eric Dumazet]

On Thu, Dec 1, 2022 at 9:44 PM George Kennedy <george.kennedy@oracle.com> wrote:
>
>
>
> On 12/1/2022 2:25 PM, Eric Dumazet wrote:
> > On Thu, Dec 1, 2022 at 2:16 PM Pavan Chebbi <pavan.chebbi@broadcom.com> wrote:
> >> On Wed, Nov 30, 2022 at 7:43 PM George Kennedy
> >> <george.kennedy@oracle.com> wrote:
> >>> The dev pointer can be NULL in dev_hard_header(). Add check for dev being
> >>> NULL in dev_hard_header() to avoid GPF.
> >>>
> >>> general protection fault, probably for non-canonical address
> >>>      0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
> >>> KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
> >>> CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
> >>> Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
> >>> Workqueue: mld mld_ifc_work
> >>> RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
> >>>      (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
> >>> RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
> >>> RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
> >>> RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
> >>> RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
> >>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
> >>> R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
> >>> FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
> >>>      knlGS:0000000000000000
> >>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
> >>> Call Trace:
> >>>   <TASK>
> >>> neigh_connected_output (./include/linux/netdevice.h:3060
> >>>      net/core/neighbour.c:1595)
> >>> ip6_finish_output2 (./include/net/neighbour.h:546
> >>>      net/ipv6/ip6_output.c:134)
> >>> ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
> >>> ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
> >>> NF_HOOK.constprop.0 (./include/net/dst.h:445
> >>>      ./include/linux/netfilter.h:302)
> >>> mld_sendpack (net/ipv6/mcast.c:1824)
> >>> mld_send_cr (net/ipv6/mcast.c:2122)
> >>> mld_ifc_work (net/ipv6/mcast.c:2655)
> >>> process_one_work (kernel/workqueue.c:2294)
> >>> worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
> >>> kthread (kernel/kthread.c:376)
> >>> ret_from_fork (arch/x86/entry/entry_64.S:312)
> >>>   </TASK>
> >>> Modules linked in:
> >>> Dumping ftrace buffer:
> >>>     (ftrace buffer empty)
> >>> ---[ end trace 0000000000000000 ]---
> >>>
> >>> Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
> >>> Reported-by: syzkaller <syzkaller@googlegroups.com>
> >>> Signed-off-by: George Kennedy <george.kennedy@oracle.com>
> >>> ---
> >>>   include/linux/netdevice.h | 2 +-
> >>>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> >>> index eddf8ee270e7..9b25a6301fa5 100644
> >>> --- a/include/linux/netdevice.h
> >>> +++ b/include/linux/netdevice.h
> >>> @@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
> >>>                                    const void *daddr, const void *saddr,
> >>>                                    unsigned int len)
> >>>   {
> >>> -       if (!dev->header_ops || !dev->header_ops->create)
> >>> +       if (!dev || !dev->header_ops || !dev->header_ops->create)
> > Do  you have a repro ?
> See syzkaller repros attached.
>
> > This patch will not prevent a crash later I think.
>
> The repro ran overnight without failure with the patch applied.

Yes, but the patch is hiding a potential bug that might show up with
other 'repros'



>
> >
> > Please fix the root cause, thanks !
>
> Will try.

Thanks, having a repro definitely should help to find the real bug.

I took a look at macvlan , and could not see how vlan->lowerdev  could
be NULL in the first place.

>
> Thanks,
> George
> >
> >>>                  return 0;
> >> net_device being NULL during eth header construction? seems like a
> >> more serious issue?
> >> If it indeed is a genuine scenario I think a better description is needed...
> >>
> >>>          return dev->header_ops->create(skb, dev, type, daddr, saddr, len);
> >>> --
> >>> 2.31.1
> >>>

Re: [PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[George Kennedy]

Hi Eric,

More info...

On 12/1/2022 11:11 PM, Eric Dumazet wrote:
> On Thu, Dec 1, 2022 at 9:44 PM George Kennedy <george.kennedy@oracle.com> wrote:
>>
>>
>> On 12/1/2022 2:25 PM, Eric Dumazet wrote:
>>> On Thu, Dec 1, 2022 at 2:16 PM Pavan Chebbi <pavan.chebbi@broadcom.com> wrote:
>>>> On Wed, Nov 30, 2022 at 7:43 PM George Kennedy
>>>> <george.kennedy@oracle.com> wrote:
>>>>> The dev pointer can be NULL in dev_hard_header(). Add check for dev being
>>>>> NULL in dev_hard_header() to avoid GPF.
>>>>>
>>>>> general protection fault, probably for non-canonical address
>>>>>       0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
>>>>> KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
>>>>> CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
>>>>> Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
>>>>> Workqueue: mld mld_ifc_work
>>>>> RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
>>>>>       (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
>>>>> RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
>>>>> RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
>>>>> RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
>>>>> RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
>>>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
>>>>> R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
>>>>> FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
>>>>>       knlGS:0000000000000000
>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>> CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
>>>>> Call Trace:
>>>>>    <TASK>
>>>>> neigh_connected_output (./include/linux/netdevice.h:3060
>>>>>       net/core/neighbour.c:1595)
>>>>> ip6_finish_output2 (./include/net/neighbour.h:546
>>>>>       net/ipv6/ip6_output.c:134)
>>>>> ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
>>>>> ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
>>>>> NF_HOOK.constprop.0 (./include/net/dst.h:445
>>>>>       ./include/linux/netfilter.h:302)
>>>>> mld_sendpack (net/ipv6/mcast.c:1824)
>>>>> mld_send_cr (net/ipv6/mcast.c:2122)
>>>>> mld_ifc_work (net/ipv6/mcast.c:2655)
>>>>> process_one_work (kernel/workqueue.c:2294)
>>>>> worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
>>>>> kthread (kernel/kthread.c:376)
>>>>> ret_from_fork (arch/x86/entry/entry_64.S:312)
>>>>>    </TASK>
>>>>> Modules linked in:
>>>>> Dumping ftrace buffer:
>>>>>      (ftrace buffer empty)
>>>>> ---[ end trace 0000000000000000 ]---
>>>>>
>>>>> Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
>>>>> Reported-by: syzkaller <syzkaller@googlegroups.com>
>>>>> Signed-off-by: George Kennedy <george.kennedy@oracle.com>
>>>>> ---
>>>>>    include/linux/netdevice.h | 2 +-
>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>>>> index eddf8ee270e7..9b25a6301fa5 100644
>>>>> --- a/include/linux/netdevice.h
>>>>> +++ b/include/linux/netdevice.h
>>>>> @@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
>>>>>                                     const void *daddr, const void *saddr,
>>>>>                                     unsigned int len)
>>>>>    {
>>>>> -       if (!dev->header_ops || !dev->header_ops->create)
>>>>> +       if (!dev || !dev->header_ops || !dev->header_ops->create)
>>> Do  you have a repro ?
>> See syzkaller repros attached.
>>
>>> This patch will not prevent a crash later I think.
>> The repro ran overnight without failure with the patch applied.
> Yes, but the patch is hiding a potential bug that might show up with
> other 'repros'
The repro fails when these devices are configured (seem like small mtu):

20: vxcan0@vxcan1: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UP group default qlen 1000
     link/can
     inet 172.20.20.38/24 scope global vxcan0
        valid_lft forever preferred_lft forever
21: vxcan1@vxcan0: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UP group default qlen 1000
     link/can
     inet 172.20.20.39/24 scope global vxcan1
        valid_lft forever preferred_lft forever


# diff ../config.fail .config
3325c3325
< CONFIG_CAN_VXCAN=y
---
> # CONFIG_CAN_VXCAN is not set

Thanks,
George

>>> Please fix the root cause, thanks !
>> Will try.
> Thanks, having a repro definitely should help to find the real bug.
>
> I took a look at macvlan , and could not see how vlan->lowerdev  could
> be NULL in the first place.
>
>> Thanks,
>> George
>>>>>                   return 0;
>>>> net_device being NULL during eth header construction? seems like a
>>>> more serious issue?
>>>> If it indeed is a genuine scenario I think a better description is needed...
>>>>
>>>>>           return dev->header_ops->create(skb, dev, type, daddr, saddr, len);
>>>>> --
>>>>> 2.31.1
>>>>>

Re: [PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[Eric Dumazet]

On Tue, Dec 6, 2022 at 2:11 AM George Kennedy <george.kennedy@oracle.com> wrote:
>
> Hi Eric,
>
> More info...
>
> On 12/1/2022 11:11 PM, Eric Dumazet wrote:
> > On Thu, Dec 1, 2022 at 9:44 PM George Kennedy <george.kennedy@oracle.com> wrote:
> >>
> >>
> >> On 12/1/2022 2:25 PM, Eric Dumazet wrote:
> >>> On Thu, Dec 1, 2022 at 2:16 PM Pavan Chebbi <pavan.chebbi@broadcom.com> wrote:
> >>>> On Wed, Nov 30, 2022 at 7:43 PM George Kennedy
> >>>> <george.kennedy@oracle.com> wrote:
> >>>>> The dev pointer can be NULL in dev_hard_header(). Add check for dev being
> >>>>> NULL in dev_hard_header() to avoid GPF.
> >>>>>
> >>>>> general protection fault, probably for non-canonical address
> >>>>>       0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
> >>>>> KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
> >>>>> CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
> >>>>> Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
> >>>>> Workqueue: mld mld_ifc_work
> >>>>> RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
> >>>>>       (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
> >>>>> RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
> >>>>> RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
> >>>>> RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
> >>>>> RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
> >>>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
> >>>>> R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
> >>>>> FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
> >>>>>       knlGS:0000000000000000
> >>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>>>> CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
> >>>>> Call Trace:
> >>>>>    <TASK>
> >>>>> neigh_connected_output (./include/linux/netdevice.h:3060
> >>>>>       net/core/neighbour.c:1595)
> >>>>> ip6_finish_output2 (./include/net/neighbour.h:546
> >>>>>       net/ipv6/ip6_output.c:134)
> >>>>> ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
> >>>>> ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
> >>>>> NF_HOOK.constprop.0 (./include/net/dst.h:445
> >>>>>       ./include/linux/netfilter.h:302)
> >>>>> mld_sendpack (net/ipv6/mcast.c:1824)
> >>>>> mld_send_cr (net/ipv6/mcast.c:2122)
> >>>>> mld_ifc_work (net/ipv6/mcast.c:2655)
> >>>>> process_one_work (kernel/workqueue.c:2294)
> >>>>> worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
> >>>>> kthread (kernel/kthread.c:376)
> >>>>> ret_from_fork (arch/x86/entry/entry_64.S:312)
> >>>>>    </TASK>
> >>>>> Modules linked in:
> >>>>> Dumping ftrace buffer:
> >>>>>      (ftrace buffer empty)
> >>>>> ---[ end trace 0000000000000000 ]---
> >>>>>
> >>>>> Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
> >>>>> Reported-by: syzkaller <syzkaller@googlegroups.com>
> >>>>> Signed-off-by: George Kennedy <george.kennedy@oracle.com>
> >>>>> ---
> >>>>>    include/linux/netdevice.h | 2 +-
> >>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> >>>>> index eddf8ee270e7..9b25a6301fa5 100644
> >>>>> --- a/include/linux/netdevice.h
> >>>>> +++ b/include/linux/netdevice.h
> >>>>> @@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
> >>>>>                                     const void *daddr, const void *saddr,
> >>>>>                                     unsigned int len)
> >>>>>    {
> >>>>> -       if (!dev->header_ops || !dev->header_ops->create)
> >>>>> +       if (!dev || !dev->header_ops || !dev->header_ops->create)
> >>> Do  you have a repro ?
> >> See syzkaller repros attached.
> >>
> >>> This patch will not prevent a crash later I think.
> >> The repro ran overnight without failure with the patch applied.
> > Yes, but the patch is hiding a potential bug that might show up with
> > other 'repros'
> The repro fails when these devices are configured (seem like small mtu):
>
> 20: vxcan0@vxcan1: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UP group default qlen 1000
>      link/can
>      inet 172.20.20.38/24 scope global vxcan0
>         valid_lft forever preferred_lft forever
> 21: vxcan1@vxcan0: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UP group default qlen 1000
>      link/can
>      inet 172.20.20.39/24 scope global vxcan1
>         valid_lft forever preferred_lft forever
>
>
> # diff ../config.fail .config
> 3325c3325
> < CONFIG_CAN_VXCAN=y
> ---
> > # CONFIG_CAN_VXCAN is not set
>
> Thanks,
> George

Small MTU has caused numerous issues in the past.

I am pretty sure we miss some READ_ONCE(dev->mtu) and other safety checks.

Re: [PATCH] net: check for dev pointer being NULL in dev_hard_header() to avoid GPF

[George Kennedy]

Hi Eric,

On 12/5/2022 10:21 PM, Eric Dumazet wrote:
> On Tue, Dec 6, 2022 at 2:11 AM George Kennedy <george.kennedy@oracle.com> wrote:
>> Hi Eric,
>>
>> More info...
>>
>> On 12/1/2022 11:11 PM, Eric Dumazet wrote:
>>> On Thu, Dec 1, 2022 at 9:44 PM George Kennedy <george.kennedy@oracle.com> wrote:
>>>>
>>>> On 12/1/2022 2:25 PM, Eric Dumazet wrote:
>>>>> On Thu, Dec 1, 2022 at 2:16 PM Pavan Chebbi <pavan.chebbi@broadcom.com> wrote:
>>>>>> On Wed, Nov 30, 2022 at 7:43 PM George Kennedy
>>>>>> <george.kennedy@oracle.com> wrote:
>>>>>>> The dev pointer can be NULL in dev_hard_header(). Add check for dev being
>>>>>>> NULL in dev_hard_header() to avoid GPF.
>>>>>>>
>>>>>>> general protection fault, probably for non-canonical address
>>>>>>>        0xdffffc0000000046: 0000 [#1] PREEMPT SMP KASAN NOPTI
>>>>>>> KASAN: null-ptr-deref in range [0x0000000000000230-0x0000000000000237]
>>>>>>> CPU: 1 PID: 45 Comm: kworker/1:1 Not tainted 6.1.0-rc7+ #2
>>>>>>> Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0+20659+3dcf7c70
>>>>>>> Workqueue: mld mld_ifc_work
>>>>>>> RIP: 0010:macvlan_hard_header (./include/linux/netdevice.h:3057
>>>>>>>        (discriminator 4) drivers/net/macvlan.c:594 (discriminator 4))
>>>>>>> RSP: 0018:ffff888103d377d0 EFLAGS: 00010212
>>>>>>> RAX: dffffc0000000000 RBX: ffff88801cf1a000 RCX: 0000000000000000
>>>>>>> RDX: 0000000000000046 RSI: 0000000000000000 RDI: 0000000000000230
>>>>>>> RBP: ffff88801e8ef328 R08: 0000000000000000 R09: 0000000000000060
>>>>>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88801f0497c0
>>>>>>> R13: 0000000000000000 R14: ffff888045187c98 R15: 0000000000000060
>>>>>>> FS:  0000000000000000(0000) GS:ffff888106c80000(0000)
>>>>>>>        knlGS:0000000000000000
>>>>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>>> CR2: 00007fbf3f1c1840 CR3: 0000000014e36000 CR4: 00000000000006e0
>>>>>>> Call Trace:
>>>>>>>     <TASK>
>>>>>>> neigh_connected_output (./include/linux/netdevice.h:3060
>>>>>>>        net/core/neighbour.c:1595)
>>>>>>> ip6_finish_output2 (./include/net/neighbour.h:546
>>>>>>>        net/ipv6/ip6_output.c:134)
>>>>>>> ip6_finish_output (net/ipv6/ip6_output.c:195 net/ipv6/ip6_output.c:206)
>>>>>>> ip6_output (./include/linux/netfilter.h:291 net/ipv6/ip6_output.c:227)
>>>>>>> NF_HOOK.constprop.0 (./include/net/dst.h:445
>>>>>>>        ./include/linux/netfilter.h:302)
>>>>>>> mld_sendpack (net/ipv6/mcast.c:1824)
>>>>>>> mld_send_cr (net/ipv6/mcast.c:2122)
>>>>>>> mld_ifc_work (net/ipv6/mcast.c:2655)
>>>>>>> process_one_work (kernel/workqueue.c:2294)
>>>>>>> worker_thread (./include/linux/list.h:292 kernel/workqueue.c:2437)
>>>>>>> kthread (kernel/kthread.c:376)
>>>>>>> ret_from_fork (arch/x86/entry/entry_64.S:312)
>>>>>>>     </TASK>
>>>>>>> Modules linked in:
>>>>>>> Dumping ftrace buffer:
>>>>>>>       (ftrace buffer empty)
>>>>>>> ---[ end trace 0000000000000000 ]---
>>>>>>>
>>>>>>> Fixes: 0c4e85813d0a ("[NET]: Wrap netdevice hardware header creation.")
>>>>>>> Reported-by: syzkaller <syzkaller@googlegroups.com>
>>>>>>> Signed-off-by: George Kennedy <george.kennedy@oracle.com>
>>>>>>> ---
>>>>>>>     include/linux/netdevice.h | 2 +-
>>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>>>>>> index eddf8ee270e7..9b25a6301fa5 100644
>>>>>>> --- a/include/linux/netdevice.h
>>>>>>> +++ b/include/linux/netdevice.h
>>>>>>> @@ -3054,7 +3054,7 @@ static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
>>>>>>>                                      const void *daddr, const void *saddr,
>>>>>>>                                      unsigned int len)
>>>>>>>     {
>>>>>>> -       if (!dev->header_ops || !dev->header_ops->create)
>>>>>>> +       if (!dev || !dev->header_ops || !dev->header_ops->create)
>>>>> Do  you have a repro ?
>>>> See syzkaller repros attached.
>>>>
>>>>> This patch will not prevent a crash later I think.
>>>> The repro ran overnight without failure with the patch applied.
>>> Yes, but the patch is hiding a potential bug that might show up with
>>> other 'repros'
>> The repro fails when these devices are configured (seem like small mtu):
>>
>> 20: vxcan0@vxcan1: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UP group default qlen 1000
>>       link/can
>>       inet 172.20.20.38/24 scope global vxcan0
>>          valid_lft forever preferred_lft forever
>> 21: vxcan1@vxcan0: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UP group default qlen 1000
>>       link/can
>>       inet 172.20.20.39/24 scope global vxcan1
>>          valid_lft forever preferred_lft forever
>>
>>
>> # diff ../config.fail .config
>> 3325c3325
>> < CONFIG_CAN_VXCAN=y
>> ---
>>> # CONFIG_CAN_VXCAN is not set
>> Thanks,
>> George
> Small MTU has caused numerous issues in the past.
>
> I am pretty sure we miss some READ_ONCE(dev->mtu) and other safety checks.

I have not been able to find the root-cause of the "vxcan" related GPF 
yet. What I do know is that for the GPF to occur:
1) CONFIG_CAN_VXCAN=y must be set
2) if CONFIG_CAN_VXCAN=y is set, the GPF will not occur if "vxcan" is 
commented out of the C reproducer

C reproducer with "vxcan" commented out (GPF will not occur):

# diff -C 3 repro_macvlan1.c repro_macvlan1_no_vsxcan.c
*** repro_macvlan1.c    2022-12-06 01:03:47.557094544 +0000
--- repro_macvlan1_no_vsxcan.c    2022-12-12 13:15:05.293719169 +0000
***************
*** 884,890 ****
         {"vcan", "vcan0"},           {"bond", "bond0"},
         {"team", "team0"},           {"dummy", "dummy0"},
         {"nlmon", "nlmon0"},         {"caif", "caif0"},
!       {"batadv", "batadv0"},       {"vxcan", "vxcan1"},
         {"netdevsim", netdevsim},    {"veth", 0},
         {"xfrm", "xfrm0"},           {"wireguard", "wg0"},
         {"wireguard", "wg1"},        {"wireguard", "wg2"},
--- 884,893 ----
         {"vcan", "vcan0"},           {"bond", "bond0"},
         {"team", "team0"},           {"dummy", "dummy0"},
         {"nlmon", "nlmon0"},         {"caif", "caif0"},
!       {"batadv", "batadv0"},
! #ifdef VXCAN
!       {"vxcan", "vxcan1"},
! #endif
         {"netdevsim", netdevsim},    {"veth", 0},
         {"xfrm", "xfrm0"},           {"wireguard", "wg0"},
         {"wireguard", "wg1"},        {"wireguard", "wg2"},
***************
*** 923,930 ****
--- 926,935 ----
         {"hsr0", 0},
         {"dummy0", ETH_ALEN},
         {"nlmon0", 0},
+ #ifdef VXCAN
         {"vxcan0", 0, true},
         {"vxcan1", 0, true},
+ #endif
         {"caif0", ETH_ALEN},
         {"batadv0", ETH_ALEN},
         {netdevsim, ETH_ALEN},

I think for now until the vxcan related GPF root-cause is found, the 
"dev NULL check" patch should go in. The "dev NULL check" patch is on 
same line as 2 other NULL checks.

Could you try the original C reproducer with kernel with 
CONFIG_CAN_VXCAN=y set to see if you have any insights as to the GPF 
root-cause?

Thank you,
George