ksmbd: check strictly data area in ksmbd_smb2_check_message()

When invalid data offset and data length in request,
ksmbd_smb2_check_message check strictly and doesn't allow to process such
requests.

Cc: Tom Talpey <tom@talpey.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Böhme <slow@samba.org>
Acked-by: Hyunchul Lee <hyc.lee@gmail.com>
Reviewed-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/ksmbd/smb2misc.c b/fs/ksmbd/smb2misc.c
index 9aa46bb..9edd9c1 100644 (file)
--- a/fs/ksmbd/smb2misc.c
+++ b/fs/ksmbd/smb2misc.c
@@ -80,18 +80,21 @@ static const bool has_smb2_data_area[NUMBER_OF_SMB2_COMMANDS] = {
 };
 
 /*
- * Returns the pointer to the beginning of the data area. Length of the data
- * area and the offset to it (from the beginning of the smb are also returned.
+ * Set length of the data area and the offset to arguments.
+ * if they are invalid, return error.
  */
-static char *smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *hdr)
+static int smb2_get_data_area_len(unsigned int *off, unsigned int *len,
+                                 struct smb2_hdr *hdr)
 {
+       int ret = 0;
+
        *off = 0;
        *len = 0;
 
        /* error reqeusts do not have data area */
        if (hdr->Status && hdr->Status != STATUS_MORE_PROCESSING_REQUIRED &&
            (((struct smb2_err_rsp *)hdr)->StructureSize) == SMB2_ERROR_STRUCTURE_SIZE2_LE)
-               return NULL;
+               return ret;
 
        /*
         * Following commands have data areas so we have to get the location
@@ -165,69 +168,60 @@ static char *smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *hdr)
        case SMB2_IOCTL:
                *off = le32_to_cpu(((struct smb2_ioctl_req *)hdr)->InputOffset);
                *len = le32_to_cpu(((struct smb2_ioctl_req *)hdr)->InputCount);
-
                break;
        default:
                ksmbd_debug(SMB, "no length check for command\n");
                break;
        }
 
-       /*
-        * Invalid length or offset probably means data area is invalid, but
-        * we have little choice but to ignore the data area in this case.
-        */
        if (*off > 4096) {
-               ksmbd_debug(SMB, "offset %d too large, data area ignored\n",
-                           *off);
-               *len = 0;
-               *off = 0;
-       } else if (*off < 0) {
-               ksmbd_debug(SMB,
-                           "negative offset %d to data invalid ignore data area\n",
-                           *off);
-               *off = 0;
-               *len = 0;
-       } else if (*len < 0) {
-               ksmbd_debug(SMB,
-                           "negative data length %d invalid, data area ignored\n",
-                           *len);
-               *len = 0;
-       } else if (*len > 128 * 1024) {
-               ksmbd_debug(SMB, "data area larger than 128K: %d\n", *len);
-               *len = 0;
+               ksmbd_debug(SMB, "offset %d too large\n", *off);
+               ret = -EINVAL;
+       } else if ((u64)*off + *len > MAX_STREAM_PROT_LEN) {
+               ksmbd_debug(SMB, "Request is larger than maximum stream protocol length(%u): %llu\n",
+                           MAX_STREAM_PROT_LEN, (u64)*off + *len);
+               ret = -EINVAL;
        }
 
-       /* return pointer to beginning of data area, ie offset from SMB start */
-       if ((*off != 0) && (*len != 0))
-               return (char *)hdr + *off;
-       else
-               return NULL;
+       return ret;
 }
 
 /*
  * Calculate the size of the SMB message based on the fixed header
  * portion, the number of word parameters and the data portion of the message.
  */
-static unsigned int smb2_calc_size(void *buf)
+static int smb2_calc_size(void *buf, unsigned int *len)
 {
        struct smb2_pdu *pdu = (struct smb2_pdu *)buf;
        struct smb2_hdr *hdr = &pdu->hdr;
-       int offset; /* the offset from the beginning of SMB to data area */
-       int data_length; /* the length of the variable length data area */
+       unsigned int offset; /* the offset from the beginning of SMB to data area */
+       unsigned int data_length; /* the length of the variable length data area */
+       int ret;
+
        /* Structure Size has already been checked to make sure it is 64 */
-       int len = le16_to_cpu(hdr->StructureSize);
+       *len = le16_to_cpu(hdr->StructureSize);
 
        /*
         * StructureSize2, ie length of fixed parameter area has already
         * been checked to make sure it is the correct length.
         */
-       len += le16_to_cpu(pdu->StructureSize2);
+       *len += le16_to_cpu(pdu->StructureSize2);
+       /*
+        * StructureSize2 of smb2_lock pdu is set to 48, indicating
+        * the size of smb2 lock request with single smb2_lock_element
+        * regardless of number of locks. Subtract single
+        * smb2_lock_element for correct buffer size check.
+        */
+       if (hdr->Command == SMB2_LOCK)
+               *len -= sizeof(struct smb2_lock_element);
 
        if (has_smb2_data_area[le16_to_cpu(hdr->Command)] == false)
                goto calc_size_exit;
 
-       smb2_get_data_area_len(&offset, &data_length, hdr);
-       ksmbd_debug(SMB, "SMB2 data length %d offset %d\n", data_length,
+       ret = smb2_get_data_area_len(&offset, &data_length, hdr);
+       if (ret)
+               return ret;
+       ksmbd_debug(SMB, "SMB2 data length %u offset %u\n", data_length,
                    offset);
 
        if (data_length > 0) {
@@ -237,16 +231,19 @@ static unsigned int smb2_calc_size(void *buf)
                 * for some commands, typically those with odd StructureSize,
                 * so we must add one to the calculation.
                 */
-               if (offset + 1 < len)
+               if (offset + 1 < *len) {
                        ksmbd_debug(SMB,
-                                   "data area offset %d overlaps SMB2 header %d\n",
-                                   offset + 1, len);
-               else
-                       len = offset + data_length;
+                                   "data area offset %d overlaps SMB2 header %u\n",
+                                   offset + 1, *len);
+                       return -EINVAL;
+               }
+
+               *len = offset + data_length;
        }
+
 calc_size_exit:
-       ksmbd_debug(SMB, "SMB2 len %d\n", len);
-       return len;
+       ksmbd_debug(SMB, "SMB2 len %u\n", *len);
+       return 0;
 }
 
 static inline int smb2_query_info_req_len(struct smb2_query_info_req *h)
@@ -391,9 +388,11 @@ int ksmbd_smb2_check_message(struct ksmbd_work *work)
                return 1;
        }
 
-       clc_len = smb2_calc_size(hdr);
+       if (smb2_calc_size(hdr, &clc_len))
+               return 1;
+
        if (len != clc_len) {
-               /* server can return one byte more due to implied bcc[0] */
+               /* client can return one byte more due to implied bcc[0] */
                if (clc_len == len + 1)
                        return 0;
 
@@ -418,9 +417,6 @@ int ksmbd_smb2_check_message(struct ksmbd_work *work)
                        return 0;
                }
 
-               if (command == SMB2_LOCK_HE && len == 88)
-                       return 0;
-
                ksmbd_debug(SMB,
                            "cli req too short, len %d not %d. cmd:%d mid:%llu\n",
                            len, clc_len, command,