Commit 266b9fec authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Steve French
Browse files

cifs: cifspdu.h: Replace zero-length array with flexible-array member 

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21


[3] commit 76497732 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent ba55344f

fs/cifs/cifspdu.h

+9 −9
Original line number Diff line number Diff line
@@ -1021,7 +1021,7 @@ typedef struct smb_com_writex_req { 
	__le16 ByteCount;

	__u8 Pad;		/* BB check for whether padded to DWORD

				   boundary and optimum performance here */

	char Data[0];

	char Data[];

} __attribute__((packed)) WRITEX_REQ;



typedef struct smb_com_write_req {
@@ -1041,7 +1041,7 @@ typedef struct smb_com_write_req { 
	__le16 ByteCount;

	__u8 Pad;		/* BB check for whether padded to DWORD

				   boundary and optimum performance here */

	char Data[0];

	char Data[];

} __attribute__((packed)) WRITE_REQ;



typedef struct smb_com_write_rsp {
@@ -1306,7 +1306,7 @@ typedef struct smb_com_ntransact_req { 
	/* SetupCount words follow then */

	__le16 ByteCount;

	__u8 Pad[3];

	__u8 Parms[0];

	__u8 Parms[];

} __attribute__((packed)) NTRANSACT_REQ;



typedef struct smb_com_ntransact_rsp {
@@ -1523,7 +1523,7 @@ struct file_notify_information { 
	__le32 NextEntryOffset;

	__le32 Action;

	__le32 FileNameLength;

	__u8  FileName[0];

	__u8  FileName[];

} __attribute__((packed));



/* For IO_REPARSE_TAG_SYMLINK */
@@ -1536,7 +1536,7 @@ struct reparse_symlink_data { 
	__le16	PrintNameOffset;

	__le16	PrintNameLength;

	__le32	Flags;

	char	PathBuffer[0];

	char	PathBuffer[];

} __attribute__((packed));



/* Flag above */
@@ -1553,7 +1553,7 @@ struct reparse_posix_data { 
	__le16	ReparseDataLength;

	__u16	Reserved;

	__le64	InodeType; /* LNK, FIFO, CHR etc. */

	char	PathBuffer[0];

	char	PathBuffer[];

} __attribute__((packed));



struct cifs_quota_data {
@@ -1762,7 +1762,7 @@ struct set_file_rename { 
	__le32 overwrite;   /* 1 = overwrite dest */

	__u32 root_fid;   /* zero */

	__le32 target_name_len;

	char  target_name[0];  /* Must be unicode */

	char  target_name[];  /* Must be unicode */

} __attribute__((packed));



struct smb_com_transaction2_sfi_req {
@@ -2451,7 +2451,7 @@ struct cifs_posix_acl { /* access conrol list (ACL) */ 
	__le16	version;

	__le16	access_entry_count;  /* access ACL - count of entries */

	__le16	default_entry_count; /* default ACL - count of entries */

	struct cifs_posix_ace ace_array[0];

	struct cifs_posix_ace ace_array[];

	/* followed by

	struct cifs_posix_ace default_ace_arraay[] */

} __attribute__((packed));  /* level 0x204 */
@@ -2757,7 +2757,7 @@ typedef struct file_xattr_info { 
	/* BB do we need another field for flags? BB */

	__u32 xattr_name_len;

	__u32 xattr_value_len;

	char  xattr_name[0];

	char  xattr_name[];

	/* followed by xattr_value[xattr_value_len], no pad */

} __attribute__((packed)) FILE_XATTR_INFO; /* extended attribute info

					      level 0x205 */

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