ccid_hc_tx_send_packet might be called with a NULL ccid pointer
leading to a NULL pointer dereference
Below mentioned commit has similarly changes
commit 276bdb82dedb ("dccp: check ccid before dereferencing")
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
Signed-off-by: Bragatheswaran Manickavel <[email protected]>
---
net/dccp/ccid.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index 105f3734dadb..1015dc2b9392 100644
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
struct sk_buff *skb)
{
- if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
+ if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
return CCID_PACKET_SEND_AT_ONCE;
}
--
2.34.1
On Sat, Oct 28, 2023 at 4:41 PM Bragatheswaran Manickavel
<[email protected]> wrote:
>
> ccid_hc_tx_send_packet might be called with a NULL ccid pointer
> leading to a NULL pointer dereference
>
> Below mentioned commit has similarly changes
> commit 276bdb82dedb ("dccp: check ccid before dereferencing")
>
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
> Signed-off-by: Bragatheswaran Manickavel <[email protected]>
> ---
> net/dccp/ccid.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
> index 105f3734dadb..1015dc2b9392 100644
> --- a/net/dccp/ccid.h
> +++ b/net/dccp/ccid.h
> @@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
> static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
> struct sk_buff *skb)
> {
> - if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> + if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
> return CCID_PACKET_SEND_AT_ONCE;
> }
> --
> 2.34.1
>
If you are willing to fix dccp, I would make sure that some of
lockless accesses to dccps_hc_tx_ccid
are also double checked and fixed.
do_dccp_getsockopt() and dccp_get_info()
On 30/10/23 14:29, Eric Dumazet wrote:
> On Sat, Oct 28, 2023 at 4:41 PM Bragatheswaran Manickavel
> <[email protected]> wrote:
>> ccid_hc_tx_send_packet might be called with a NULL ccid pointer
>> leading to a NULL pointer dereference
>>
>> Below mentioned commit has similarly changes
>> commit 276bdb82dedb ("dccp: check ccid before dereferencing")
>>
>> Reported-by: [email protected]
>> Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
>> Signed-off-by: Bragatheswaran Manickavel <[email protected]>
>> ---
>> net/dccp/ccid.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
>> index 105f3734dadb..1015dc2b9392 100644
>> --- a/net/dccp/ccid.h
>> +++ b/net/dccp/ccid.h
>> @@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
>> static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
>> struct sk_buff *skb)
>> {
>> - if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
>> + if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
>> return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
>> return CCID_PACKET_SEND_AT_ONCE;
>> }
>> --
>> 2.34.1
>>
> If you are willing to fix dccp, I would make sure that some of
> lockless accesses to dccps_hc_tx_ccid
> are also double checked and fixed.
>
> do_dccp_getsockopt() and dccp_get_info()
Hi Eric,
In both do_dccp_getsockopt() and dccp_get_info(), dccps_hc_rx_ccid are
checked properly before access.
Thanks,
Bragathe
On Mon, Oct 30, 2023 at 4:40 PM Bragatheswaran Manickavel
<[email protected]> wrote:
>
>
> On 30/10/23 14:29, Eric Dumazet wrote:
> > On Sat, Oct 28, 2023 at 4:41 PM Bragatheswaran Manickavel
> > <[email protected]> wrote:
> >> ccid_hc_tx_send_packet might be called with a NULL ccid pointer
> >> leading to a NULL pointer dereference
> >>
> >> Below mentioned commit has similarly changes
> >> commit 276bdb82dedb ("dccp: check ccid before dereferencing")
> >>
> >> Reported-by: [email protected]
> >> Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
> >> Signed-off-by: Bragatheswaran Manickavel <[email protected]>
> >> ---
> >> net/dccp/ccid.h | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
> >> index 105f3734dadb..1015dc2b9392 100644
> >> --- a/net/dccp/ccid.h
> >> +++ b/net/dccp/ccid.h
> >> @@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
> >> static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
> >> struct sk_buff *skb)
> >> {
> >> - if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> >> + if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> >> return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
> >> return CCID_PACKET_SEND_AT_ONCE;
> >> }
> >> --
> >> 2.34.1
> >>
> > If you are willing to fix dccp, I would make sure that some of
> > lockless accesses to dccps_hc_tx_ccid
> > are also double checked and fixed.
> >
> > do_dccp_getsockopt() and dccp_get_info()
>
>
> Hi Eric,
>
> In both do_dccp_getsockopt() and dccp_get_info(), dccps_hc_rx_ccid are
> checked properly before access.
>
Not really, because another thread can change the value at the same time.
Adding checks is not solving races.
On Mon, Oct 30, 2023 at 5:22 PM Bragatheswaran Manickavel
<[email protected]> wrote:
>
>
> On 30/10/23 21:19, Eric Dumazet wrote:
>
> On Mon, Oct 30, 2023 at 4:40 PM Bragatheswaran Manickavel
> <[email protected]> wrote:
>
> On 30/10/23 14:29, Eric Dumazet wrote:
>
> On Sat, Oct 28, 2023 at 4:41 PM Bragatheswaran Manickavel
> <[email protected]> wrote:
>
> ccid_hc_tx_send_packet might be called with a NULL ccid pointer
> leading to a NULL pointer dereference
>
> Below mentioned commit has similarly changes
> commit 276bdb82dedb ("dccp: check ccid before dereferencing")
>
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
> Signed-off-by: Bragatheswaran Manickavel <[email protected]>
> ---
> net/dccp/ccid.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
> index 105f3734dadb..1015dc2b9392 100644
> --- a/net/dccp/ccid.h
> +++ b/net/dccp/ccid.h
> @@ -163,7 +163,7 @@ static inline int ccid_packet_dequeue_eval(const int return_code)
> static inline int ccid_hc_tx_send_packet(struct ccid *ccid, struct sock *sk,
> struct sk_buff *skb)
> {
> - if (ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> + if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_send_packet != NULL)
> return ccid->ccid_ops->ccid_hc_tx_send_packet(sk, skb);
> return CCID_PACKET_SEND_AT_ONCE;
> }
> --
> 2.34.1
>
> If you are willing to fix dccp, I would make sure that some of
> lockless accesses to dccps_hc_tx_ccid
> are also double checked and fixed.
>
> do_dccp_getsockopt() and dccp_get_info()
>
> Hi Eric,
>
> In both do_dccp_getsockopt() and dccp_get_info(), dccps_hc_rx_ccid are
> checked properly before access.
>
> Not really, because another thread can change the value at the same time.
>
> Adding checks is not solving races.
>
> Understood. But when I see function similar to ccid_hc_tx_send_packet all of
> them has ccid check and few of them have addressed same issue.
>
> dccp_get_info()
> if (dp->dccps_hc_rx_ccid != NULL)
> ccid_hc_rx_get_info(dp->dccps_hc_rx_ccid, sk, info);
> if (dp->dccps_hc_tx_ccid != NULL)
> ccid_hc_tx_get_info(dp->dccps_hc_tx_ccid, sk, info);
>
All I am saying is that these changes are not correct.
They are simply adding some 'checks' that are unsafe.
Compiler can absolutely fetch dp->dccps_hc_tx_ccid a second time,
and a NULL could be read this second time.
> do_dccp_getsockopt()
> ccid_hc_rx_getsockopt
> ccid_hc_tx_getsockopt
> ccid_get_current_rx_ccid
> ccid_get_current_tx_ccid ===> All of them have ccid check
>
> So, I went on with this changes.
> If you have another suggestion of fixing this issue please let me know. I will take a look.
On Sat, 2023-10-28 at 20:11 +0530, Bragatheswaran Manickavel wrote:
> ccid_hc_tx_send_packet might be called with a NULL ccid pointer
> leading to a NULL pointer dereference
You should describe how such event could happen.
> Below mentioned commit has similarly changes
> commit 276bdb82dedb ("dccp: check ccid before dereferencing")
>
> Reported-by: [email protected]
> Closes: https://syzkaller.appspot.com/bug?extid=c71bc336c5061153b502
and add a suitable fixes here.
(beyond taking care of other critical code paths, as reported by Eric).
Thanks!
Paolo