[CIFS] Workaround incomplete byte length returned by some

servers on small SMB responses

Signed-off-by: Steve French <sfrench@us.ibm.com>

2 files changed, 30 insertions, 14 deletions

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 4a4fd2dbca63..f1f8225102f0 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -55,7 +55,7 @@ extern int SendReceiveBlockingLock(const unsigned int /* xid */ ,
                                 struct smb_hdr * /* input */ ,
                                 struct smb_hdr * /* out */ ,
                                 int * /* bytes returned */);
-extern int checkSMB(struct smb_hdr *smb, __u16 mid, int length);
+extern int checkSMB(struct smb_hdr *smb, __u16 mid, unsigned int length);
 extern int is_valid_oplock_break(struct smb_hdr *smb, struct TCP_Server_Info *);
 extern int is_size_safe_to_change(struct cifsInodeInfo *);
 extern struct cifsFileInfo *find_writable_file(struct cifsInodeInfo *);
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index ca6e9b1413fa..bbc9cd34b6ea 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -418,26 +418,42 @@ checkSMBhdr(struct smb_hdr *smb, __u16 mid)
 }
 
 int
-checkSMB(struct smb_hdr *smb, __u16 mid, int length)
+checkSMB(struct smb_hdr *smb, __u16 mid, unsigned int length)
 {
         __u32 len = smb->smb_buf_length;
         __u32 clc_len;  /* calculated length */
         cFYI(0, ("checkSMB Length: 0x%x, smb_buf_length: 0x%x", length, len));
-        if (((unsigned int)length < 2 + sizeof (struct smb_hdr)) ||
-            (len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4)) {
-                if ((unsigned int)length < 2 + sizeof (struct smb_hdr)) {
-                        if (((unsigned int)length >= 
-                                sizeof (struct smb_hdr) - 1)
+
+        if (length < 2 + sizeof (struct smb_hdr)) {
+                if ((length >= sizeof (struct smb_hdr) - 1)
                             && (smb->Status.CifsError != 0)) {
-                                smb->WordCount = 0;
-                                /* some error cases do not return wct and bcc */
+                        smb->WordCount = 0;
+                        /* some error cases do not return wct and bcc */
+                        return 0;
+                } else if ((length == sizeof(struct smb_hdr) + 1) && 
+                                (smb->WordCount == 0)) {
+                        char * tmp = (char *)smb;
+                        /* Need to work around a bug in two servers here */
+                        /* First, check if the part of bcc they sent was zero */
+                        if (tmp[sizeof(struct smb_hdr)] == 0) {
+                                /* some servers return only half of bcc
+                                 * on simple responses (wct, bcc both zero)
+                                 * in particular have seen this on
+                                 * ulogoffX and FindClose. This leaves
+                                 * one byte of bcc potentially unitialized
+                                 */
+                                /* zero rest of bcc */
+                                tmp[sizeof(struct smb_hdr)+1] = 0;
                                 return 0;
-                        } else {
-                                cERROR(1, ("Length less than smb header size"));
                         }
+                        cERROR(1,("rcvd invalid byte count (bcc)"));
+                } else {
+                        cERROR(1, ("Length less than smb header size"));
                 }
-                if (len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4)
-                        cERROR(1, ("smb length greater than MaxBufSize, mid=%d",
+                return 1;
+        }
+        if (len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4) {
+                cERROR(1, ("smb length greater than MaxBufSize, mid=%d",
                                    smb->Mid));
                 return 1;
         }
@@ -446,7 +462,7 @@ checkSMB(struct smb_hdr *smb, __u16 mid, int length)
                 return 1;
         clc_len = smbCalcSize_LE(smb);
 
-        if(4 + len != (unsigned int)length) {
+        if(4 + len != length) {
                 cERROR(1, ("Length read does not match RFC1001 length %d",len));
                 return 1;
         }