1 files changed, 44 insertions, 8 deletions

diff --git a/fs/smb/client/smb2misc.c b/fs/smb/client/smb2misc.c
index 2a7355ce1a07..9068175e57cd 100644
--- a/fs/smb/client/smb2misc.c
+++ b/fs/smb/client/smb2misc.c
@@ -19,6 +19,9 @@
 #include "nterr.h"
 #include "cached_dir.h"
 
+static unsigned int __smb2_calc_size(void *buf, bool *have_data,
+				     bool *data_area_overlap);
+
 static int
 check_smb2_hdr(struct smb2_hdr *shdr, __u64 mid)
 {
@@ -145,6 +148,8 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
 	int command;
 	__u32 calc_len; /* calculated length */
 	__u64 mid;
+	bool have_data;
+	bool data_area_overlap;
 
 	/* If server is a channel, select the primary channel */
 	pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;
@@ -228,7 +233,13 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
 		}
 	}
 
-	calc_len = smb2_calc_size(buf);
+	have_data = false;
+	data_area_overlap = false;
+	calc_len = __smb2_calc_size(buf, &have_data, &data_area_overlap);
+
+	/* Reject responses whose data area overlaps the fixed area. */
+	if (data_area_overlap)
+		return 1;
 
 	/* For SMB2_IOCTL, OutputOffset and OutputLength are optional, so might
 	 * be 0, and not a real miscalculation */
@@ -247,8 +258,13 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
 		/* Windows 7 server returns 24 bytes more */
 		if (calc_len + 24 == len && command == SMB2_OPLOCK_BREAK_HE)
 			return 0;
-		/* server can return one byte more due to implied bcc[0] */
-		if (calc_len == len + 1)
+		/*
+		 * Server can return one byte more due to implied bcc[0].
+		 * Allow it only when there is no data area; if data_length > 0
+		 * the +1 gap indicates an overreported data length rather than
+		 * the bcc[0] omission.
+		 */
+		if (calc_len == len + 1 && !have_data)
 			return 0;
 
 		/*
@@ -407,19 +423,28 @@ smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *shdr)
 }
 
 /*
- * 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.
+ * Calculate the size of the SMB message based on the fixed header, fixed
+ * parameter area, and variable data area.
+ *
+ * If have_data is not NULL, it is set when a non-empty data area is found.
+ * If data_area_overlap is not NULL, it is set when the data area overlaps
+ * the fixed area.
  */
-unsigned int
-smb2_calc_size(void *buf)
+static unsigned int
+__smb2_calc_size(void *buf, bool *have_data, bool *data_area_overlap)
 {
 	struct smb2_pdu *pdu = buf;
 	struct smb2_hdr *shdr = &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 */
+	int data_length = 0; /* the length of the variable length data area */
 	/* Structure Size has already been checked to make sure it is 64 */
 	int len = le16_to_cpu(shdr->StructureSize);
 
+	if (have_data)
+		*have_data = false;
+	if (data_area_overlap)
+		*data_area_overlap = false;
+
 	/*
 	 * StructureSize2, ie length of fixed parameter area has already
 	 * been checked to make sure it is the correct length.
@@ -442,16 +467,27 @@ smb2_calc_size(void *buf)
 		if (offset + 1 < len) {
 			cifs_dbg(VFS, "data area offset %d overlaps SMB2 header %d\n",
 				 offset + 1, len);
+			if (data_area_overlap)
+				*data_area_overlap = true;
 			data_length = 0;
+			goto calc_size_exit;
 		} else {
 			len = offset + data_length;
 		}
 	}
 calc_size_exit:
 	cifs_dbg(FYI, "SMB2 len %d\n", len);
+	if (have_data)
+		*have_data = (data_length > 0);
 	return len;
 }
 
+unsigned int
+smb2_calc_size(void *buf)
+{
+	return __smb2_calc_size(buf, NULL, NULL);
+}
+
 /* Note: caller must free return buffer */
 __le16 *
 cifs_convert_path_to_utf16(const char *from, struct cifs_sb_info *cifs_sb)