fixes for four CIFS/SMB3 potential pointer overflow issues, one minor build fix, and a build warning cleanup

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Merge tag '4.19-rc3-smb3-cifs' of git://git.samba.org/sfrench/cifs-2.6

Pull cifs fixes from Steve French:
 "Fixes for four CIFS/SMB3 potential pointer overflow issues, one minor
  build fix, and a build warning cleanup"

* tag '4.19-rc3-smb3-cifs' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: read overflow in is_valid_oplock_break()
  cifs: integer overflow in in SMB2_ioctl()
  CIFS: fix wrapping bugs in num_entries()
  cifs: prevent integer overflow in nxt_dir_entry()
  fs/cifs: require sha512
  fs/cifs: suppress a string overflow warning

fs/cifs/Kconfig

@@ -6,6 +6,7 @@ config CIFS
 	select CRYPTO_MD4
 	select CRYPTO_MD5
 	select CRYPTO_SHA256
+	select CRYPTO_SHA512
 	select CRYPTO_CMAC
 	select CRYPTO_HMAC
 	select CRYPTO_ARC4

fs/cifs/cifssmb.c

@@ -601,10 +601,15 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses *ses)
 	}
 
 	count = 0;
+	/*
+	 * We know that all the name entries in the protocols array
+	 * are short (< 16 bytes anyway) and are NUL terminated.
+	 */
 	for (i = 0; i < CIFS_NUM_PROT; i++) {
-		strncpy(pSMB->DialectsArray+count, protocols[i].name, 16);
+		size_t len = strlen(protocols[i].name) + 1;
-		count += strlen(protocols[i].name) + 1;
+
-		/* null at end of source and target buffers anyway */
+		memcpy(pSMB->DialectsArray+count, protocols[i].name, len);
+		count += len;
 	}
 	inc_rfc1001_len(pSMB, count);
 	pSMB->ByteCount = cpu_to_le16(count);

fs/cifs/misc.c

@@ -402,9 +402,17 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv)
 			(struct smb_com_transaction_change_notify_rsp *)buf;
 		struct file_notify_information *pnotify;
 		__u32 data_offset = 0;
+		size_t len = srv->total_read - sizeof(pSMBr->hdr.smb_buf_length);
+
 		if (get_bcc(buf) > sizeof(struct file_notify_information)) {
 			data_offset = le32_to_cpu(pSMBr->DataOffset);
 
+			if (data_offset >
+			    len - sizeof(struct file_notify_information)) {
+				cifs_dbg(FYI, "invalid data_offset %u\n",
+					 data_offset);
+				return true;
+			}
 			pnotify = (struct file_notify_information *)
 				((char *)&pSMBr->hdr.Protocol + data_offset);
 			cifs_dbg(FYI, "dnotify on %s Action: 0x%x\n",

fs/cifs/readdir.c

@@ -376,8 +376,15 @@ static char *nxt_dir_entry(char *old_entry, char *end_of_smb, int level)
 
 		new_entry = old_entry + sizeof(FIND_FILE_STANDARD_INFO) +
 				pfData->FileNameLength;
-	} else
+	} else {
-		new_entry = old_entry + le32_to_cpu(pDirInfo->NextEntryOffset);
+		u32 next_offset = le32_to_cpu(pDirInfo->NextEntryOffset);
+
+		if (old_entry + next_offset < old_entry) {
+			cifs_dbg(VFS, "invalid offset %u\n", next_offset);
+			return NULL;
+		}
+		new_entry = old_entry + next_offset;
+	}
 	cifs_dbg(FYI, "new entry %p old entry %p\n", new_entry, old_entry);
 	/* validate that new_entry is not past end of SMB */
 	if (new_entry >= end_of_smb) {

fs/cifs/smb2pdu.c

@@ -2459,14 +2459,14 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
 	/* We check for obvious errors in the output buffer length and offset */
 	if (*plen == 0)
 		goto ioctl_exit; /* server returned no data */
-	else if (*plen > 0xFF00) {
+	else if (*plen > rsp_iov.iov_len || *plen > 0xFF00) {
 		cifs_dbg(VFS, "srv returned invalid ioctl length: %d\n", *plen);
 		*plen = 0;
 		rc = -EIO;
 		goto ioctl_exit;
 	}
 
-	if (rsp_iov.iov_len < le32_to_cpu(rsp->OutputOffset) + *plen) {
+	if (rsp_iov.iov_len - *plen < le32_to_cpu(rsp->OutputOffset)) {
 		cifs_dbg(VFS, "Malformed ioctl resp: len %d offset %d\n", *plen,
 			le32_to_cpu(rsp->OutputOffset));
 		*plen = 0;
@@ -3577,33 +3577,38 @@ num_entries(char *bufstart, char *end_of_buf, char **lastentry, size_t size)
 	int len;
 	unsigned int entrycount = 0;
 	unsigned int next_offset = 0;
-	FILE_DIRECTORY_INFO *entryptr;
+	char *entryptr;
+	FILE_DIRECTORY_INFO *dir_info;
 
 	if (bufstart == NULL)
 		return 0;
 
-	entryptr = (FILE_DIRECTORY_INFO *)bufstart;
+	entryptr = bufstart;
 
 	while (1) {
-		entryptr = (FILE_DIRECTORY_INFO *)
+		if (entryptr + next_offset < entryptr ||
-					((char *)entryptr + next_offset);
+		    entryptr + next_offset > end_of_buf ||
-
+		    entryptr + next_offset + size > end_of_buf) {
-		if ((char *)entryptr + size > end_of_buf) {
 			cifs_dbg(VFS, "malformed search entry would overflow\n");
 			break;
 		}
 
-		len = le32_to_cpu(entryptr->FileNameLength);
+		entryptr = entryptr + next_offset;
-		if ((char *)entryptr + len + size > end_of_buf) {
+		dir_info = (FILE_DIRECTORY_INFO *)entryptr;
+
+		len = le32_to_cpu(dir_info->FileNameLength);
+		if (entryptr + len < entryptr ||
+		    entryptr + len > end_of_buf ||
+		    entryptr + len + size > end_of_buf) {
 			cifs_dbg(VFS, "directory entry name would overflow frame end of buf %p\n",
 				 end_of_buf);
 			break;
 		}
 
-		*lastentry = (char *)entryptr;
+		*lastentry = entryptr;
 		entrycount++;
 
-		next_offset = le32_to_cpu(entryptr->NextEntryOffset);
+		next_offset = le32_to_cpu(dir_info->NextEntryOffset);
 		if (!next_offset)
 			break;
 	}