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

D. Wythe
2024-08-13T08:52:26Z

On 8/13/24 4:05 PM, Gerd Bayer wrote:
> On Sun, 2024-08-11 at 02:22 +0900, 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.
> I can not argue substantially with that... There's very little IPv6
> testing that I'm aware of. But do you really need to move that much
> code around and change whitespace for you fix?
>
> [--- snip ---]
>
>
>> 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. */
>> +
>>  };

Hi Jeongjun,

I have no problem with this fix, thank you for your assistance.
But, what this here was for ?

>>
>>  #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..3c54faef6042 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;
>> +};
>> +
>>  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),

Since you have done alignment, why not align the  '='.

> The line above together with the definition of struct smc6_sock seem to
> be the only changes relevant to fixing the issue, IMHO.
>
>>  };
>>
>>  static const struct proto_ops smc_inet6_stream_ops = {
>> --
>>
> Thanks, Gerd