smb3: Replace smb2pdu 1-element arrays with flex-arrays

The kernel is globally removing the ambiguous 0-length and 1-element
arrays in favor of flexible arrays, so that we can gain both compile-time
and run-time array bounds checking[1].

Replace the trailing 1-element array with a flexible array in the
following structures:

	struct smb2_err_rsp
	struct smb2_tree_connect_req
	struct smb2_negotiate_rsp
	struct smb2_sess_setup_req
	struct smb2_sess_setup_rsp
	struct smb2_read_req
	struct smb2_read_rsp
	struct smb2_write_req
	struct smb2_write_rsp
	struct smb2_query_directory_req
	struct smb2_query_directory_rsp
	struct smb2_set_info_req
	struct smb2_change_notify_rsp
	struct smb2_create_rsp
	struct smb2_query_info_req
	struct smb2_query_info_rsp

Replace the trailing 1-element array with a flexible array, but leave
the existing structure padding:

	struct smb2_file_all_info
	struct smb2_lock_req

Adjust all related size calculations to match the changes to sizeof().

No machine code output or .data section differences are produced after
these changes.

[1] For lots of details, see both:
    https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
    https://people.kernel.org/kees/bounded-flexible-arrays-in-c

Cc: Steve French <sfrench@samba.org>
Cc: Paulo Alcantara <pc@cjr.nz>
Cc: Ronnie Sahlberg <lsahlber@redhat.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 24 insertions, 18 deletions

diff --git a/fs/smbfs_common/smb2pdu.h b/fs/smbfs_common/smb2pdu.h
index 7d605db3bb3b..ace133cf6072 100644
--- a/fs/smbfs_common/smb2pdu.h
+++ b/fs/smbfs_common/smb2pdu.h
@@ -167,7 +167,7 @@ struct smb2_err_rsp {
 	__u8   ErrorContextCount;
 	__u8   Reserved;
 	__le32 ByteCount;  /* even if zero, at least one byte follows */
-	__u8   ErrorData[1];  /* variable length */
+	__u8   ErrorData[];  /* variable length */
 } __packed;
 
 #define SMB3_AES_CCM_NONCE 11
@@ -308,7 +308,7 @@ struct smb2_tree_connect_req {
 	__le16 Flags;		/* Flags in SMB3.1.1 */
 	__le16 PathOffset;
 	__le16 PathLength;
-	__u8   Buffer[1];	/* variable length */
+	__u8   Buffer[];	/* variable length */
 } __packed;
 
 /* Possible ShareType values */
@@ -595,7 +595,7 @@ struct smb2_negotiate_rsp {
 	__le16 SecurityBufferOffset;
 	__le16 SecurityBufferLength;
 	__le32 NegotiateContextOffset;	/* Pre:SMB3.1.1 was reserved/ignored */
-	__u8   Buffer[1];	/* variable length GSS security buffer */
+	__u8   Buffer[];	/* variable length GSS security buffer */
 } __packed;
 
 
@@ -616,7 +616,7 @@ struct smb2_sess_setup_req {
 	__le16 SecurityBufferOffset;
 	__le16 SecurityBufferLength;
 	__le64 PreviousSessionId;
-	__u8   Buffer[1];	/* variable length GSS security buffer */
+	__u8   Buffer[];	/* variable length GSS security buffer */
 } __packed;
 
 /* Currently defined SessionFlags */
@@ -633,7 +633,7 @@ struct smb2_sess_setup_rsp {
 	__le16 SessionFlags;
 	__le16 SecurityBufferOffset;
 	__le16 SecurityBufferLength;
-	__u8   Buffer[1];	/* variable length GSS security buffer */
+	__u8   Buffer[];	/* variable length GSS security buffer */
 } __packed;
 
 
@@ -715,7 +715,7 @@ struct smb2_read_req {
 	__le32 RemainingBytes;
 	__le16 ReadChannelInfoOffset;
 	__le16 ReadChannelInfoLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 /* Read flags */
@@ -730,7 +730,7 @@ struct smb2_read_rsp {
 	__le32 DataLength;
 	__le32 DataRemaining;
 	__le32 Flags;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 
@@ -754,7 +754,7 @@ struct smb2_write_req {
 	__le16 WriteChannelInfoOffset;
 	__le16 WriteChannelInfoLength;
 	__le32 Flags;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_write_rsp {
@@ -765,7 +765,7 @@ struct smb2_write_rsp {
 	__le32 DataLength;
 	__le32 DataRemaining;
 	__u32  Reserved2;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 
@@ -812,7 +812,10 @@ struct smb2_lock_req {
 	__u64  PersistentFileId;
 	__u64  VolatileFileId;
 	/* Followed by at least one */
-	struct smb2_lock_element locks[1];
+	union {
+		struct smb2_lock_element lock;
+		DECLARE_FLEX_ARRAY(struct smb2_lock_element, locks);
+	};
 } __packed;
 
 struct smb2_lock_rsp {
@@ -866,7 +869,7 @@ struct smb2_query_directory_req {
 	__le16 FileNameOffset;
 	__le16 FileNameLength;
 	__le32 OutputBufferLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_query_directory_rsp {
@@ -874,7 +877,7 @@ struct smb2_query_directory_rsp {
 	__le16 StructureSize; /* Must be 9 */
 	__le16 OutputBufferOffset;
 	__le32 OutputBufferLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 /*
@@ -897,7 +900,7 @@ struct smb2_set_info_req {
 	__le32 AdditionalInformation;
 	__u64  PersistentFileId;
 	__u64  VolatileFileId;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_set_info_rsp {
@@ -952,7 +955,7 @@ struct smb2_change_notify_rsp {
 	__le16	StructureSize;  /* Must be 9 */
 	__le16	OutputBufferOffset;
 	__le32	OutputBufferLength;
-	__u8	Buffer[1]; /* array of file notify structs */
+	__u8	Buffer[]; /* array of file notify structs */
 } __packed;
 
 
@@ -1158,7 +1161,7 @@ struct smb2_create_rsp {
 	__u64  VolatileFileId;
 	__le32 CreateContextsOffset;
 	__le32 CreateContextsLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct create_posix {
@@ -1501,7 +1504,7 @@ struct smb2_query_info_req {
 	__le32 Flags;
 	__u64  PersistentFileId;
 	__u64  VolatileFileId;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 struct smb2_query_info_rsp {
@@ -1509,7 +1512,7 @@ struct smb2_query_info_rsp {
 	__le16 StructureSize; /* Must be 9 */
 	__le16 OutputBufferOffset;
 	__le32 OutputBufferLength;
-	__u8   Buffer[1];
+	__u8   Buffer[];
 } __packed;
 
 /*
@@ -1570,7 +1573,10 @@ struct smb2_file_all_info { /* data block encoding of response to level 18 */
 	__le32 Mode;
 	__le32 AlignmentRequirement;
 	__le32 FileNameLength;
-	char   FileName[1];
+	union {
+		char __pad;	/* Legacy structure padding */
+		DECLARE_FLEX_ARRAY(char, FileName);
+	};
 } __packed; /* level 18 Query */
 
 struct smb2_file_eof_info { /* encoding of request for level 10 */