[CIFS] Allow null nd (as nfs server uses) on create

While creating a file on a server which supports unix extensions
such as Samba, if a file is being created which does not supply
nameidata (i.e. nd is null), cifs client can oops when calling
cifs_posix_open.
Signed-off-by: Shirish Pargaonkar <shirishp@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifsproto.h

@@ -107,7 +107,9 @@ extern struct cifsFileInfo *cifs_new_fileinfo(struct inode *newinode,
 				__u16 fileHandle, struct file *file,
 				struct vfsmount *mnt, unsigned int oflags);
 extern int cifs_posix_open(char *full_path, struct inode **pinode,
-			   struct vfsmount *mnt, int mode, int oflags,
+				struct vfsmount *mnt,
+				struct super_block *sb,
+				int mode, int oflags,
 				__u32 *poplock, __u16 *pnetfid, int xid);
 extern void cifs_unix_basic_to_fattr(struct cifs_fattr *fattr,
 				     FILE_UNIX_BASIC_INFO *info,

fs/cifs/dir.c

@@ -182,13 +182,14 @@ cifs_new_fileinfo(struct inode *newinode, __u16 fileHandle,
 }
 
 int cifs_posix_open(char *full_path, struct inode **pinode,
-		    struct vfsmount *mnt, int mode, int oflags,
+			struct vfsmount *mnt, struct super_block *sb,
+			int mode, int oflags,
 			__u32 *poplock, __u16 *pnetfid, int xid)
 {
 	int rc;
 	FILE_UNIX_BASIC_INFO *presp_data;
 	__u32 posix_flags = 0;
-	struct cifs_sb_info *cifs_sb = CIFS_SB(mnt->mnt_sb);
+	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
 	struct cifs_fattr fattr;
 
 	cFYI(1, "posix open %s", full_path);
@@ -241,7 +242,7 @@ int cifs_posix_open(char *full_path, struct inode **pinode,
 
 	/* get new inode and set it up */
 	if (*pinode == NULL) {
-		*pinode = cifs_iget(mnt->mnt_sb, &fattr);
+		*pinode = cifs_iget(sb, &fattr);
 		if (!*pinode) {
 			rc = -ENOMEM;
 			goto posix_open_ret;
@@ -250,6 +251,7 @@ int cifs_posix_open(char *full_path, struct inode **pinode,
 		cifs_fattr_to_inode(*pinode, &fattr);
 	}
 
+	if (mnt)
 		cifs_new_fileinfo(*pinode, *pnetfid, NULL, mnt, oflags);
 
 posix_open_ret:
@@ -314,13 +316,14 @@ cifs_create(struct inode *inode, struct dentry *direntry, int mode,
 	if (nd && (nd->flags & LOOKUP_OPEN))
 		oflags = nd->intent.open.flags;
 	else
-		oflags = FMODE_READ;
+		oflags = FMODE_READ | SMB_O_CREAT;
 
 	if (tcon->unix_ext && (tcon->ses->capabilities & CAP_UNIX) &&
 	    (CIFS_UNIX_POSIX_PATH_OPS_CAP &
 			le64_to_cpu(tcon->fsUnixInfo.Capability))) {
-		rc = cifs_posix_open(full_path, &newinode, nd->path.mnt,
-				     mode, oflags, &oplock, &fileHandle, xid);
+		rc = cifs_posix_open(full_path, &newinode,
+			nd ? nd->path.mnt : NULL,
+			inode->i_sb, mode, oflags, &oplock, &fileHandle, xid);
 		/* EIO could indicate that (posix open) operation is not
 		   supported, despite what server claimed in capability
 		   negotation.  EREMOTE indicates DFS junction, which is not
@@ -677,6 +680,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 		     (nd->flags & LOOKUP_OPEN) && !pTcon->broken_posix_open &&
 		     (nd->intent.open.flags & O_CREAT)) {
 			rc = cifs_posix_open(full_path, &newInode, nd->path.mnt,
+					parent_dir_inode->i_sb,
 					nd->intent.open.create_mode,
 					nd->intent.open.flags, &oplock,
 					&fileHandle, xid);

fs/cifs/file.c

@@ -298,8 +298,10 @@ int cifs_open(struct inode *inode, struct file *file)
 	    (CIFS_UNIX_POSIX_PATH_OPS_CAP &
 			le64_to_cpu(tcon->fsUnixInfo.Capability))) {
 		int oflags = (int) cifs_posix_convert_flags(file->f_flags);
+		oflags |= SMB_O_CREAT;
 		/* can not refresh inode info since size could be stale */
 		rc = cifs_posix_open(full_path, &inode, file->f_path.mnt,
+				inode->i_sb,
 				cifs_sb->mnt_file_mode /* ignored */,
 				oflags, &oplock, &netfid, xid);
 		if (rc == 0) {
@@ -513,6 +515,7 @@ static int cifs_reopen_file(struct file *file, bool can_flush)
 		int oflags = (int) cifs_posix_convert_flags(file->f_flags);
 		/* can not refresh inode info since size could be stale */
 		rc = cifs_posix_open(full_path, NULL, file->f_path.mnt,
+				inode->i_sb,
 				cifs_sb->mnt_file_mode /* ignored */,
 				oflags, &oplock, &netfid, xid);
 		if (rc == 0) {