smb: client, common: fix fortify warnings

When compiling with gcc version 14.0.0 20231126 (experimental)
and CONFIG_FORTIFY_SOURCE=y, I've noticed the following:

In file included from ./include/linux/string.h:295,
from ./include/linux/bitmap.h:12,
from ./include/linux/cpumask.h:12,
from ./arch/x86/include/asm/paravirt.h:17,
from ./arch/x86/include/asm/cpuid.h:62,
from ./arch/x86/include/asm/processor.h:19,
from ./arch/x86/include/asm/cpufeature.h:5,
from ./arch/x86/include/asm/thread_info.h:53,
from ./include/linux/thread_info.h:60,
from ./arch/x86/include/asm/preempt.h:9,
from ./include/linux/preempt.h:79,
from ./include/linux/spinlock.h:56,
from ./include/linux/wait.h:9,
from ./include/linux/wait_bit.h:8,
from ./include/linux/fs.h:6,
from fs/smb/client/smb2pdu.c:18:
In function 'fortify_memcpy_chk',
inlined from '__SMB2_close' at fs/smb/client/smb2pdu.c:3480:4:
./include/linux/fortify-string.h:588:25: warning: call to '__read_overflow2_field'
declared with attribute warning: detected read beyond size of field (2nd parameter);
maybe use struct_group()? [-Wattribute-warning]
588 | __read_overflow2_field(q_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

and:

In file included from ./include/linux/string.h:295,
from ./include/linux/bitmap.h:12,
from ./include/linux/cpumask.h:12,
from ./arch/x86/include/asm/paravirt.h:17,
from ./arch/x86/include/asm/cpuid.h:62,
from ./arch/x86/include/asm/processor.h:19,
from ./arch/x86/include/asm/cpufeature.h:5,
from ./arch/x86/include/asm/thread_info.h:53,
from ./include/linux/thread_info.h:60,
from ./arch/x86/include/asm/preempt.h:9,
from ./include/linux/preempt.h:79,
from ./include/linux/spinlock.h:56,
from ./include/linux/wait.h:9,
from ./include/linux/wait_bit.h:8,
from ./include/linux/fs.h:6,
from fs/smb/client/cifssmb.c:17:
In function 'fortify_memcpy_chk',
inlined from 'CIFS_open' at fs/smb/client/cifssmb.c:1248:3:
./include/linux/fortify-string.h:588:25: warning: call to '__read_overflow2_field'
declared with attribute warning: detected read beyond size of field (2nd parameter);
maybe use struct_group()? [-Wattribute-warning]
588 | __read_overflow2_field(q_size_field, size);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In both cases, the fortification logic inteprets calls to 'memcpy()' as an
attempts to copy an amount of data which exceeds the size of the specified
field (i.e. more than 8 bytes from __le64 value) and thus issues an overread
warning. Both of these warnings may be silenced by using the convenient
'struct_group()' quirk.

Signed-off-by: Dmitry Antipov <[e-mail]>
Acked-by: Namjae Jeon <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/client/cifspdu.h

···
 	__u8 OplockLevel;
 	__u16 Fid;
 	__le32 CreateAction;
-	__le64 CreationTime;
-	__le64 LastAccessTime;
-	__le64 LastWriteTime;
-	__le64 ChangeTime;
-	__le32 FileAttributes;
+	struct_group(common_attributes,
+		__le64 CreationTime;
+		__le64 LastAccessTime;
+		__le64 LastWriteTime;
+		__le64 ChangeTime;
+		__le32 FileAttributes;
+	);
 	__le64 AllocationSize;
 	__le64 EndOfFile;
 	__le16 FileType;
···
 /* QueryFileInfo/QueryPathinfo (also for SetPath/SetFile) data buffer formats */
 /******************************************************************************/
 typedef struct { /* data block encoding of response to level 263 QPathInfo */
-	__le64 CreationTime;
-	__le64 LastAccessTime;
-	__le64 LastWriteTime;
-	__le64 ChangeTime;
-	__le32 Attributes;
+	struct_group(common_attributes,
+		__le64 CreationTime;
+		__le64 LastAccessTime;
+		__le64 LastWriteTime;
+		__le64 ChangeTime;
+		__le32 Attributes;
+	);
 	__u32 Pad1;
 	__le64 AllocationSize;
 	__le64 EndOfFile;	/* size ie offset to first free byte in file */

fs/smb/client/cifssmb.c

···
 		*oplock |= CIFS_CREATE_ACTION;
 
 	if (buf) {
-		/* copy from CreationTime to Attributes */
-		memcpy((char *)buf, (char *)&rsp->CreationTime, 36);
+		/* copy commonly used attributes */
+		memcpy(&buf->common_attributes,
+		       &rsp->common_attributes,
+		       sizeof(buf->common_attributes));
 		/* the file_info buf is endian converted by caller */
 		buf->AllocationSize = rsp->AllocationSize;
 		buf->EndOfFile = rsp->EndOfFile;

fs/smb/client/smb2pdu.c

···
 	} else {
 		trace_smb3_close_done(xid, persistent_fid, tcon->tid,
 				      ses->Suid);
-		/*
-		 * Note that have to subtract 4 since struct network_open_info
-		 * has a final 4 byte pad that close response does not have
-		 */
 		if (pbuf)
-			memcpy(pbuf, (char *)&rsp->CreationTime, sizeof(*pbuf) - 4);
+			memcpy(&pbuf->network_open_info,
+			       &rsp->network_open_info,
+			       sizeof(pbuf->network_open_info));
 	}
 
 	atomic_dec(&tcon->num_remote_opens);

fs/smb/client/smb2pdu.h

···
 } __packed;
 
 struct smb2_file_network_open_info {
-	__le64 CreationTime;
-	__le64 LastAccessTime;
-	__le64 LastWriteTime;
-	__le64 ChangeTime;
-	__le64 AllocationSize;
-	__le64 EndOfFile;
-	__le32 Attributes;
+	struct_group(network_open_info,
+		__le64 CreationTime;
+		__le64 LastAccessTime;
+		__le64 LastWriteTime;
+		__le64 ChangeTime;
+		__le64 AllocationSize;
+		__le64 EndOfFile;
+		__le32 Attributes;
+	);
 	__le32 Reserved;
 } __packed; /* level 34 Query also similar returned in close rsp and open rsp */
 

fs/smb/common/smb2pdu.h

···
 	__le16 StructureSize; /* 60 */
 	__le16 Flags;
 	__le32 Reserved;
-	__le64 CreationTime;
-	__le64 LastAccessTime;
-	__le64 LastWriteTime;
-	__le64 ChangeTime;
-	__le64 AllocationSize;	/* Beginning of FILE_STANDARD_INFO equivalent */
-	__le64 EndOfFile;
-	__le32 Attributes;
+	struct_group(network_open_info,
+		__le64 CreationTime;
+		__le64 LastAccessTime;
+		__le64 LastWriteTime;
+		__le64 ChangeTime;
+		/* Beginning of FILE_STANDARD_INFO equivalent */
+		__le64 AllocationSize;
+		__le64 EndOfFile;
+		__le32 Attributes;
+	);
 } __packed;