merged into cifs-2.6.git for-next
On Fri, Mar 6, 2020 at 5:01 PM Gustavo A. R. Silva
<gustavo@xxxxxxxxxxxxxx> wrote:
>
> 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 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> ---
> fs/cifs/cifspdu.h | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h
> index 8e15887d1f1f..593d826820c3 100644
> --- a/fs/cifs/cifspdu.h
> +++ b/fs/cifs/cifspdu.h
> @@ -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 */
> --
> 2.25.0
>
--
Thanks,
Steve
