cifs: add smb2 POSIX info level

* add new info level and structs for SMB2 posix extension
* add functions to parse and validate it
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifspdu.h

@@ -1691,6 +1691,7 @@ struct smb_t2_rsp {
 #define SMB_FIND_FILE_ID_FULL_DIR_INFO    0x105
 #define SMB_FIND_FILE_ID_BOTH_DIR_INFO    0x106
 #define SMB_FIND_FILE_UNIX                0x202
+#define SMB_FIND_FILE_POSIX_INFO          0x064
 
 typedef struct smb_com_transaction2_qpi_req {
 	struct smb_hdr hdr;	/* wct = 14+ */

fs/cifs/smb2pdu.c

@@ -4302,6 +4302,101 @@ SMB2_write(const unsigned int xid, struct cifs_io_parms *io_parms,
 	return rc;
 }
 
+static int posix_info_sid_size(const void *beg, const void *end)
+{
+	size_t subauth;
+	int total;
+
+	if (beg + 1 > end)
+		return -1;
+
+	subauth = *(u8 *)(beg+1);
+	if (subauth < 1 || subauth > 15)
+		return -1;
+
+	total = 1 + 1 + 6 + 4*subauth;
+	if (beg + total > end)
+		return -1;
+
+	return total;
+}
+
+int posix_info_parse(const void *beg, const void *end,
+		     struct smb2_posix_info_parsed *out)
+
+{
+	int total_len = 0;
+	int sid_len;
+	int name_len;
+	const void *owner_sid;
+	const void *group_sid;
+	const void *name;
+
+	/* if no end bound given, assume payload to be correct */
+	if (!end) {
+		const struct smb2_posix_info *p = beg;
+
+		end = beg + le32_to_cpu(p->NextEntryOffset);
+		/* last element will have a 0 offset, pick a sensible bound */
+		if (end == beg)
+			end += 0xFFFF;
+	}
+
+	/* check base buf */
+	if (beg + sizeof(struct smb2_posix_info) > end)
+		return -1;
+	total_len = sizeof(struct smb2_posix_info);
+
+	/* check owner sid */
+	owner_sid = beg + total_len;
+	sid_len = posix_info_sid_size(owner_sid, end);
+	if (sid_len < 0)
+		return -1;
+	total_len += sid_len;
+
+	/* check group sid */
+	group_sid = beg + total_len;
+	sid_len = posix_info_sid_size(group_sid, end);
+	if (sid_len < 0)
+		return -1;
+	total_len += sid_len;
+
+	/* check name len */
+	if (beg + total_len + 4 > end)
+		return -1;
+	name_len = le32_to_cpu(*(__le32 *)(beg + total_len));
+	if (name_len < 1 || name_len > 0xFFFF)
+		return -1;
+	total_len += 4;
+
+	/* check name */
+	name = beg + total_len;
+	if (name + name_len > end)
+		return -1;
+	total_len += name_len;
+
+	if (out) {
+		out->base = beg;
+		out->size = total_len;
+		out->name_len = name_len;
+		out->name = name;
+		memcpy(&out->owner, owner_sid,
+		       posix_info_sid_size(owner_sid, end));
+		memcpy(&out->group, group_sid,
+		       posix_info_sid_size(group_sid, end));
+	}
+	return total_len;
+}
+
+static int posix_info_extra_size(const void *beg, const void *end)
+{
+	int len = posix_info_parse(beg, end, NULL);
+
+	if (len < 0)
+		return -1;
+	return len - sizeof(struct smb2_posix_info);
+}
+
 static unsigned int
 num_entries(char *bufstart, char *end_of_buf, char **lastentry, size_t size)
 {

fs/cifs/smb2pdu.h

@@ -1613,5 +1613,49 @@ struct create_posix_rsp {
 	 * var sized group SID
 	 */
 } __packed;
+
+/*
+ * SMB2-only POSIX info level
+ *
+ * See posix_info_sid_size(), posix_info_extra_size() and
+ * posix_info_parse() to help with the handling of this struct.
+ */
+struct smb2_posix_info {
+	__le32 NextEntryOffset;
+	__u32 Ignored;
+	__le64 CreationTime;
+	__le64 LastAccessTime;
+	__le64 LastWriteTime;
+	__le64 ChangeTime;
+	__le64 EndOfFile;
+	__le64 AllocationSize;
+	__le32 DosAttributes;
+	__le64 Inode;
+	__le32 DeviceId;
+	__le32 Zero;
+	/* beginning of POSIX Create Context Response */
+	__le32 HardLinks;
+	__le32 ReparseTag;
+	__le32 Mode;
+	/*
+	 * var sized owner SID
+	 * var sized group SID
+	 * le32 filenamelength
+	 * u8  filename[]
+	 */
+} __packed;
+
+/*
+ * Parsed version of the above struct. Allows direct access to the
+ * variable length fields
+ */
+struct smb2_posix_info_parsed {
+	const struct smb2_posix_info *base;
+	size_t size;
+	struct cifs_sid owner;
+	struct cifs_sid group;
+	int name_len;
+	const u8 *name;
 };
+
 #endif				/* _SMB2PDU_H */

fs/cifs/smb2proto.h

@@ -272,4 +272,6 @@ extern int smb2_query_info_compound(const unsigned int xid,
 				    u32 class, u32 type, u32 output_len,
 				    struct kvec *rsp, int *buftype,
 				    struct cifs_sb_info *cifs_sb);
+int posix_info_parse(const void *beg, const void *end,
+		     struct smb2_posix_info_parsed *out);
 #endif			/* _SMB2PROTO_H */