CIFS: Clarify SMB1 code for POSIX Create

Coverity also complains about the way we calculate the offset
(starting from the address of a 4 byte array within the
header structure rather than from the beginning of the struct
plus 4 bytes) for SMB1 CIFSPOSIXCreate. This changeset
doesn't change the address but makes it slightly clearer.

Addresses-Coverity: 711518 ("Out of bounds write")
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index f72e3b3..d4144c1 100644 (file)
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -1081,7 +1081,8 @@ PsxCreat:
        param_offset = offsetof(struct smb_com_transaction2_spi_req,
                                InformationLevel) - 4;
        offset = param_offset + params;
        param_offset = offsetof(struct smb_com_transaction2_spi_req,
                                InformationLevel) - 4;
        offset = param_offset + params;

-       pdata = (OPEN_PSX_REQ *)(((char *)&pSMB->hdr.Protocol) + offset);
+       /* SMB offsets are from the beginning of SMB which is 4 bytes in, after RFC1001 field */
+       pdata = (OPEN_PSX_REQ *)((char *)(pSMB) + offset + 4);

        pdata->Level = cpu_to_le16(SMB_QUERY_FILE_UNIX_BASIC);
        pdata->Permissions = cpu_to_le64(mode);
        pdata->PosixOpenFlags = cpu_to_le32(posix_flags);
        pdata->Level = cpu_to_le16(SMB_QUERY_FILE_UNIX_BASIC);
        pdata->Permissions = cpu_to_le64(mode);
        pdata->PosixOpenFlags = cpu_to_le32(posix_flags);