nfsd: let nfsd_symlink assume null-terminated data

Currently nfsd_symlink has a weird hack to serve callers who don't
null-terminate symlink data: it looks ahead at the next byte to see if
it's zero, and copies it to a new buffer to null-terminate if not.

That means callers don't have to null-terminate, but they *do* have to
ensure that the byte following the end of the data is theirs to read.

That's a bit subtle, and the NFSv4 code actually got this wrong.

So let's just throw out that code and let callers pass null-terminated
strings; we've already fixed them to do that.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs3proc.c

@@ -282,7 +282,7 @@ nfsd3_proc_symlink(struct svc_rqst *rqstp, struct nfsd3_symlinkargs *argp,
 	fh_copy(&resp->dirfh, &argp->ffh);
 	fh_init(&resp->fh, NFS3_FHSIZE);
 	nfserr = nfsd_symlink(rqstp, &resp->dirfh, argp->fname, argp->flen,
-						   argp->tname, argp->tlen,
+						   argp->tname,
 						   &resp->fh, &argp->attrs);
 	RETURN_STATUS(nfserr);
 }

fs/nfsd/nfs4proc.c

@@ -623,7 +623,7 @@ nfsd4_create(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	case NF4LNK:
 		status = nfsd_symlink(rqstp, &cstate->current_fh,
 				      create->cr_name, create->cr_namelen,
-				      create->cr_linkname, create->cr_linklen,
+				      create->cr_linkname,
 				      &resfh, &create->cr_iattr);
 		break;
 

fs/nfsd/nfsproc.c

@@ -409,7 +409,7 @@ nfsd_proc_symlink(struct svc_rqst *rqstp, struct nfsd_symlinkargs *argp,
 	 */
 	argp->tname[argp->tlen] = '\0';
 	nfserr = nfsd_symlink(rqstp, &argp->ffh, argp->fname, argp->flen,
-						 argp->tname, argp->tlen,
+						 argp->tname,
 				 		 &newfh, &argp->attrs);
 
 

fs/nfsd/vfs.c

@@ -1504,7 +1504,7 @@ nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
 __be32
 nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
 				char *fname, int flen,
-				char *path,  int plen,
+				char *path,
 				struct svc_fh *resfhp,
 				struct iattr *iap)
 {
@@ -1513,7 +1513,7 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	int		host_err;
 
 	err = nfserr_noent;
-	if (!flen || !plen)
+	if (!flen || path[0] == '\0')
 		goto out;
 	err = nfserr_exist;
 	if (isdotent(fname, flen))
@@ -1534,18 +1534,7 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	if (IS_ERR(dnew))
 		goto out_nfserr;
 
-	if (unlikely(path[plen] != 0)) {
-		char *path_alloced = kmalloc(plen+1, GFP_KERNEL);
-		if (path_alloced == NULL)
-			host_err = -ENOMEM;
-		else {
-			strncpy(path_alloced, path, plen);
-			path_alloced[plen] = 0;
-			host_err = vfs_symlink(dentry->d_inode, dnew, path_alloced);
-			kfree(path_alloced);
-		}
-	} else
-		host_err = vfs_symlink(dentry->d_inode, dnew, path);
+	host_err = vfs_symlink(dentry->d_inode, dnew, path);
 	err = nfserrno(host_err);
 	if (!err)
 		err = nfserrno(commit_metadata(fhp));

fs/nfsd/vfs.h

@@ -85,7 +85,7 @@ __be32 		nfsd_write(struct svc_rqst *, struct svc_fh *,struct file *,
 __be32		nfsd_readlink(struct svc_rqst *, struct svc_fh *,
 				char *, int *);
 __be32		nfsd_symlink(struct svc_rqst *, struct svc_fh *,
-				char *name, int len, char *path, int plen,
+				char *name, int len, char *path,
 				struct svc_fh *res, struct iattr *);
 __be32		nfsd_link(struct svc_rqst *, struct svc_fh *,
 				char *, int, struct svc_fh *);