Re: [PATCH 5/7] ksmbd: add the check to vaildate if stream protocol length exceeds maximum value

[Namjae Jeon <linkinjeon@kernel.org>]

2021-09-25 17:41 GMT+09:00, Hyunchul Lee <hyc.lee@gmail.com>:
> 2021년 9월 24일 (금) 오전 11:13, Namjae Jeon <linkinjeon@kernel.org>님이 작성:
>>
>> This patch add MAX_STREAM_PROT_LEN macro and check if stream protocol
>> length exceeds maximum value. opencode pdu size check in
>> ksmbd_pdu_size_has_room().
>>
>> Cc: Tom Talpey <tom@talpey.com>
>> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
>> Cc: Ralph Böhme <slow@samba.org>
>> Cc: Steve French <smfrench@gmail.com>
>> Cc: Hyunchul Lee <hyc.lee@gmail.com>
>> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
>> Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
>> ---
>>  fs/ksmbd/connection.c | 10 ++++++----
>>  fs/ksmbd/smb_common.c |  6 ------
>>  fs/ksmbd/smb_common.h |  4 ++--
>>  3 files changed, 8 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/ksmbd/connection.c b/fs/ksmbd/connection.c
>> index af086d35398a..48b18b4ec117 100644
>> --- a/fs/ksmbd/connection.c
>> +++ b/fs/ksmbd/connection.c
>> @@ -296,10 +296,12 @@ int ksmbd_conn_handler_loop(void *p)
>>                 pdu_size = get_rfc1002_len(hdr_buf);
>>                 ksmbd_debug(CONN, "RFC1002 header %u bytes\n", pdu_size);
>>
>> -               /* make sure we have enough to get to SMB header end */
>> -               if (!ksmbd_pdu_size_has_room(pdu_size)) {
>> -                       ksmbd_debug(CONN, "SMB request too short (%u
>> bytes)\n",
>> -                                   pdu_size);
>> +               /*
>> +                * Check if pdu size is valid (min : smb header size,
>> +                * max : 0x00FFFFFF).
>> +                */
>> +               if (pdu_size < __SMB2_HEADER_STRUCTURE_SIZE ||
>> +                   pdu_size > MAX_STREAM_PROT_LEN) {
>>                         continue;
>>                 }
>>
>> diff --git a/fs/ksmbd/smb_common.c b/fs/ksmbd/smb_common.c
>> index 5901b2884c60..20bd5b8e3c0a 100644
>> --- a/fs/ksmbd/smb_common.c
>> +++ b/fs/ksmbd/smb_common.c
>> @@ -21,7 +21,6 @@ static const char basechars[43] =
>> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_-!@#$%";
>>  #define MAGIC_CHAR '~'
>>  #define PERIOD '.'
>>  #define mangle(V) ((char)(basechars[(V) % MANGLE_BASE]))
>> -#define KSMBD_MIN_SUPPORTED_HEADER_SIZE        (sizeof(struct smb2_hdr))
>>
>>  struct smb_protocol {
>>         int             index;
>> @@ -272,11 +271,6 @@ int ksmbd_init_smb_server(struct ksmbd_work *work)
>>         return 0;
>>  }
>>
>> -bool ksmbd_pdu_size_has_room(unsigned int pdu)
>> -{
>> -       return (pdu >= KSMBD_MIN_SUPPORTED_HEADER_SIZE - 4);
>> -}
>> -
>>  int ksmbd_populate_dot_dotdot_entries(struct ksmbd_work *work, int
>> info_level,
>>                                       struct ksmbd_file *dir,
>>                                       struct ksmbd_dir_info *d_info,
>> diff --git a/fs/ksmbd/smb_common.h b/fs/ksmbd/smb_common.h
>> index 994abede27e9..6e79e7577f6b 100644
>> --- a/fs/ksmbd/smb_common.h
>> +++ b/fs/ksmbd/smb_common.h
>> @@ -48,6 +48,8 @@
>>  #define CIFS_DEFAULT_IOSIZE    (64 * 1024)
>>  #define MAX_CIFS_SMALL_BUFFER_SIZE 448 /* big enough for most */
>>
>> +#define MAX_STREAM_PROT_LEN    0x00FFFFFF
>
> Do we need to append "SMB" to this macro name?
I named it with the name defined in specification. That is, no problem.
> Looks good to me.
> Acked-by: Hyunchul Lee <hyc.lee@gmail.com>
Thanks for your review!
>
>
>> +
>>  /* Responses when opening a file. */
>>  #define F_SUPERSEDED   0
>>  #define F_OPENED       1
>> @@ -493,8 +495,6 @@ int ksmbd_lookup_dialect_by_id(__le16 *cli_dialects,
>> __le16 dialects_count);
>>
>>  int ksmbd_init_smb_server(struct ksmbd_work *work);
>>
>> -bool ksmbd_pdu_size_has_room(unsigned int pdu);
>> -
>>  struct ksmbd_kstat;
>>  int ksmbd_populate_dot_dotdot_entries(struct ksmbd_work *work,
>>                                       int info_level,
>> --
>> 2.25.1
>>
>
>
> --
> Thanks,
> Hyunchul
>