Re: [PATCH net,v3] net/smc: prevent NULL pointer dereference in txopt_get

["D. Wythe" <alibuda@linux.alibaba.com>]

On 8/13/24 7:48 PM, Jeongjun Park wrote:
> D. Wythe wrote:
>>
>>
>> On 8/13/24 6:07 PM, Jeongjun Park wrote:
>>> Since smc_inet6_prot does not initialize ipv6_pinfo_offset, inet6_create()
>>> copies an incorrect address value, sk + 0 (offset), to inet_sk(sk)->pinet6.
>>>
>>> In addition, since inet_sk(sk)->pinet6 and smc_sk(sk)->clcsock practically
>>> point to the same address, when smc_create_clcsk() stores the newly
>>> created clcsock in smc_sk(sk)->clcsock, inet_sk(sk)->pinet6 is corrupted
>>> into clcsock. This causes NULL pointer dereference and various other
>>> memory corruptions.
>>>
>>> To solve this, we need to add a smc6_sock structure for ipv6_pinfo_offset
>>> initialization and modify the smc_sock structure.
>>>
>>> Reported-by: syzbot+f69bfae0a4eb29976e44@syzkaller.appspotmail.com
>>> Tested-by: syzbot+f69bfae0a4eb29976e44@syzkaller.appspotmail.com
>>> Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
>>> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
>>> ---
>>>    net/smc/smc.h      | 19 ++++++++++---------
>>>    net/smc/smc_inet.c | 24 +++++++++++++++---------
>>>    2 files changed, 25 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/net/smc/smc.h b/net/smc/smc.h
>>> index 34b781e463c4..f4d9338b5ed5 100644
>>> --- a/net/smc/smc.h
>>> +++ b/net/smc/smc.h
>>> @@ -284,15 +284,6 @@ struct smc_connection {
>>>
>>>    struct smc_sock {                           /* smc sock container */
>>>        struct sock             sk;
>>> -     struct socket           *clcsock;       /* internal tcp socket */
>>> -     void                    (*clcsk_state_change)(struct sock *sk);
>>> -                                             /* original stat_change fct. */
>>> -     void                    (*clcsk_data_ready)(struct sock *sk);
>>> -                                             /* original data_ready fct. */
>>> -     void                    (*clcsk_write_space)(struct sock *sk);
>>> -                                             /* original write_space fct. */
>>> -     void                    (*clcsk_error_report)(struct sock *sk);
>>> -                                             /* original error_report fct. */
>>>        struct smc_connection   conn;           /* smc connection */
>>>        struct smc_sock         *listen_smc;    /* listen parent */
>>>        struct work_struct      connect_work;   /* handle non-blocking connect*/
>>> @@ -325,6 +316,16 @@ struct smc_sock {                                /* smc sock container */
>>>                                                /* protects clcsock of a listen
>>>                                                 * socket
>>>                                                 * */
>>> +     struct socket           *clcsock;       /* internal tcp socket */
>>> +     void                    (*clcsk_state_change)(struct sock *sk);
>>> +                                             /* original stat_change fct. */
>>> +     void                    (*clcsk_data_ready)(struct sock *sk);
>>> +                                             /* original data_ready fct. */
>>> +     void                    (*clcsk_write_space)(struct sock *sk);
>>> +                                             /* original write_space fct. */
>>> +     void                    (*clcsk_error_report)(struct sock *sk);
>>> +                                             /* original error_report fct. */
>>> +
>>>    };
>>>
>>>    #define smc_sk(ptr) container_of_const(ptr, struct smc_sock, sk)
>>> diff --git a/net/smc/smc_inet.c b/net/smc/smc_inet.c
>>> index bece346dd8e9..25f34fd65e8d 100644
>>> --- a/net/smc/smc_inet.c
>>> +++ b/net/smc/smc_inet.c
>>> @@ -60,16 +60,22 @@ static struct inet_protosw smc_inet_protosw = {
>>>    };
>>>
>>>    #if IS_ENABLED(CONFIG_IPV6)
>>> +struct smc6_sock {
>>> +     struct smc_sock smc;
>>> +     struct ipv6_pinfo np;
>>> +};
>> I prefer to:
>>
>> struct ipv6_pinfo inet6;
> Okay, I'll write a v4 patch and send it to you tomorrow.
>
> Regards,
> Jeongjun Park

Before you issue the v4, I still don't know why you move clcsk_xxx from 
smc_connection
to smc_sock, can you explain it ?

Also, regarding alignment, it's okay for me whether it's aligned or 
not，But I checked the styles of other types of
structures and did not strictly require alignment, so I now feel that 
there is no need to
modify so much to do alignment.

D. Wythe

>
>>> +
>>>    static struct proto smc_inet6_prot = {
>>> -     .name           = "INET6_SMC",
>>> -     .owner          = THIS_MODULE,
>>> -     .init           = smc_inet_init_sock,
>>> -     .hash           = smc_hash_sk,
>>> -     .unhash         = smc_unhash_sk,
>>> -     .release_cb     = smc_release_cb,
>>> -     .obj_size       = sizeof(struct smc_sock),
>>> -     .h.smc_hash     = &smc_v6_hashinfo,
>>> -     .slab_flags     = SLAB_TYPESAFE_BY_RCU,
>>> +     .name                           = "INET6_SMC",
>>> +     .owner                          = THIS_MODULE,
>>> +     .init                           = smc_inet_init_sock,
>>> +     .hash                           = smc_hash_sk,
>>> +     .unhash                         = smc_unhash_sk,
>>> +     .release_cb                     = smc_release_cb,
>>> +     .obj_size                       = sizeof(struct smc6_sock),
>>> +     .h.smc_hash                     = &smc_v6_hashinfo,
>>> +     .slab_flags                     = SLAB_TYPESAFE_BY_RCU,
>>> +     .ipv6_pinfo_offset              = offsetof(struct smc6_sock, np),
>>>    };
>>>
>>>    static const struct proto_ops smc_inet6_stream_ops = {
>>> --