[PATCH v3 17/34] NFSD: Use xdrgen XDR functions for NFSv3 SYMLINK procedure

[Chuck Lever <cel@kernel.org>]

Replace the NFSPROC3_SYMLINK entry in the nfsd_procedures3 array
with an entry that dispatches the xdrgen-generated
nfs_svc_decode_SYMLINK3args and nfs_svc_encode_SYMLINK3res. Wrapper
structures bridge the generated xdrgen types and the legacy
svc_fh and iattr representations the NFSD VFS layer still uses.

A SYMLINK request's target pathname can extend from the head of
the receive buffer into its page data. nfsd3_proc_symlink()
reassembles it from a head segment and a single page via
svc_fill_symlink_pathname(), which copies from one page and does
not account for a page offset. Annotate the symlink_data member of
symlinkdata3 with "pragma pages" so the generated decoder
represents the pathname as a struct xdr_buf and decodes it with
svcxdr_decode_opaque_payload(), which subsegments the receive
stream instead of pulling the string inline through the bounded
xdr scratch buffer. Copy the pathname out of that xdr_buf with
nfsd_symlink_target(), which walks the head, pages, and tail of
the subsegment. The NFSv2 SYMLINK procedure already uses that
helper, so move it into vfs.c where both procedures can reach it.

Filename validity is now checked by nfsd3_proc_symlink() so that a
proper NFS3ERR status code can be returned to the client rather
than GARBAGE_ARGS.

The pc_argzero field is now set to zero for the NFSv3 SYMLINK
procedure. The xdrgen decoders are trusted to initialize all
arguments in the argp->xdrgen field, making the early defensive
memset unnecessary. The remaining argp fields are cleared as
needed.

Because nfsd3_proc_symlink() now fills in the post-op file handle,
the post-op attributes, and the WCC data, the fh_getattr() calls
are made in the proc function rather than in the XDR result
encoder, and the references to the file handles can be released
directly by nfsd3_proc_symlink(). A separate ->pc_release callback
is thus no longer needed. This makes it straightforward to
confirm that the file handles are properly released during every
error flow.

nfs3svc_decode_symlinkargs() no longer has any callers, so it is
removed.

Signed-off-by: Chuck Lever <cel@kernel.org>
---
 Documentation/sunrpc/xdr/nfs3.x    |   1 +
 fs/nfsd/nfs3proc.c                 | 120 +++++++++++++++++++++--------
 fs/nfsd/nfs3xdr.c                  |  19 -----
 fs/nfsd/nfs3xdr_gen.c              |   6 +-
 fs/nfsd/nfs3xdr_gen.h              |   2 +-
 fs/nfsd/nfsproc.c                  |  22 ------
 fs/nfsd/vfs.c                      |  29 +++++++
 fs/nfsd/vfs.h                      |   1 +
 fs/nfsd/xdr3.h                     |  11 ---
 include/linux/sunrpc/xdrgen/nfs3.h |   4 +-
 10 files changed, 123 insertions(+), 92 deletions(-)

diff --git a/Documentation/sunrpc/xdr/nfs3.x b/Documentation/sunrpc/xdr/nfs3.x
index 61b87245be1e..c987788bf34c 100644
--- a/Documentation/sunrpc/xdr/nfs3.x
+++ b/Documentation/sunrpc/xdr/nfs3.x
@@ -464,6 +464,7 @@ struct symlinkdata3 {
 	sattr3		symlink_attributes;
 	nfspath3	symlink_data;
 };
+pragma pages symlinkdata3 symlink_data;
 
 struct SYMLINK3args {
 	diropargs3	where;
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index 94751f50248a..a068b9f157d7 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -131,6 +131,22 @@ struct MKDIR3res_wrapper {
 
 static_assert(offsetof(struct MKDIR3res_wrapper, xdrgen) == 0);
 
+struct SYMLINK3args_wrapper {
+	struct SYMLINK3args	xdrgen;
+	struct svc_fh		fh;
+	struct iattr		iattrs;
+};
+
+static_assert(offsetof(struct SYMLINK3args_wrapper, xdrgen) == 0);
+
+struct SYMLINK3res_wrapper {
+	struct SYMLINK3res	xdrgen;
+	struct svc_fh		fh;
+	u8			fh_data[NFS3_FHSIZE];
+};
+
+static_assert(offsetof(struct SYMLINK3res_wrapper, xdrgen) == 0);
+
 static int	nfs3_ftypes[] = {
 	0,			/* NF3NON */
 	S_IFREG,		/* NF3REG */
@@ -1057,43 +1073,79 @@ static __be32 nfsd3_proc_mkdir(struct svc_rqst *rqstp)
 	return rpc_success;
 }
 
-static __be32
-nfsd3_proc_symlink(struct svc_rqst *rqstp)
+/**
+ * nfsd3_proc_symlink - SYMLINK: Create a symbolic link
+ * @rqstp: RPC transaction context
+ *
+ * Return:
+ *   %rpc_success:		RPC executed successfully
+ *
+ * RPC synopsis:
+ *   SYMLINK3res NFSPROC3_SYMLINK(SYMLINK3args) = 10;
+ */
+static __be32 nfsd3_proc_symlink(struct svc_rqst *rqstp)
 {
-	struct nfsd3_symlinkargs *argp = rqstp->rq_argp;
-	struct nfsd3_diropres *resp = rqstp->rq_resp;
-	struct nfsd_attrs attrs = {
-		.na_iattr	= &argp->attrs,
+	struct SYMLINK3args_wrapper *argp = rqstp->rq_argp;
+	struct symlinkdata3 *symlink = &argp->xdrgen.symlink;
+	struct xdr_buf *to = &symlink->symlink_data;
+	struct diropargs3 *where = &argp->xdrgen.where;
+	struct SYMLINK3res_wrapper *resp = rqstp->rq_resp;
+	struct iattr *iattrs = &argp->iattrs;
+	struct svc_fh *dirfhp = &argp->fh;
+	struct svc_fh *fhp = &resp->fh;
+	struct nfsd_attrs nattrs = {
+		.na_iattr	= iattrs,
 	};
+	char *tname;
 
-	if (!nfsd3_time_in_range(&argp->attrs)) {
-		resp->status = nfserr_inval;
+	nfsd3_fh3_to_svc_fh(dirfhp, &where->dir);
+	resp->xdrgen.status = nfsd3_check_filename(where->name.data,
+						   where->name.len);
+	if (resp->xdrgen.status != nfs_ok)
+		goto out;
+	nfsd3_sattr3_to_iattr(rqstp, iattrs, &symlink->symlink_attributes);
+	if (!nfsd3_time_in_range(iattrs)) {
+		resp->xdrgen.status = nfserr_inval;
 		goto out;
 	}
-	if (argp->tlen == 0) {
-		resp->status = nfserr_inval;
+	if (to->len == 0) {
+		resp->xdrgen.status = nfserr_inval;
 		goto out;
 	}
-	if (argp->tlen > NFS3_MAXPATHLEN) {
-		resp->status = nfserr_nametoolong;
+	if (to->len > NFS3_MAXPATHLEN) {
+		resp->xdrgen.status = nfserr_nametoolong;
 		goto out;
 	}
 
-	argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
-						page_address(rqstp->rq_arg.pages[0]),
-						argp->tlen);
-	if (IS_ERR(argp->tname)) {
-		resp->status = nfserrno(PTR_ERR(argp->tname));
+	tname = nfsd_symlink_target(to);
+	if (IS_ERR(tname)) {
+		resp->xdrgen.status = nfserrno(PTR_ERR(tname));
 		goto out;
 	}
 
-	fh_copy(&resp->dirfh, &argp->ffh);
-	fh_init(&resp->fh, NFS3_FHSIZE);
-	resp->status = nfsd_symlink(rqstp, &resp->dirfh, argp->fname,
-				    argp->flen, argp->tname, &attrs, &resp->fh);
-	kfree(argp->tname);
+	fh_init(fhp, NFS3_FHSIZE);
+	resp->xdrgen.status = nfsd_symlink(rqstp, dirfhp,
+					   (char *)where->name.data,
+					   where->name.len, tname,
+					   &nattrs, fhp);
+	kfree(tname);
+
 out:
-	resp->status = nfsd3_map_status(resp->status);
+	if (resp->xdrgen.status == nfs_ok) {
+		struct SYMLINK3resok *resok = &resp->xdrgen.u.resok;
+
+		nfsd3_fill_post_op_fh3(&resok->obj, fhp, resp->fh_data);
+		nfsd3_fill_post_op_attr(rqstp, &resok->obj_attributes, fhp);
+		nfsd3_fill_wcc_data(rqstp, &resok->dir_wcc, dirfhp);
+	} else {
+		struct SYMLINK3resfail *resfail = &resp->xdrgen.u.resfail;
+
+		resp->xdrgen.status = nfsd3_map_status(resp->xdrgen.status);
+		nfsd3_fill_wcc_data(rqstp, &resfail->dir_wcc, dirfhp);
+	}
+
+	fh_put(fhp);
+	fh_put(dirfhp);
 	return rpc_success;
 }
 
@@ -1578,16 +1630,15 @@ static const struct svc_procedure nfsd_procedures3[22] = {
 		.pc_name	= "MKDIR",
 	},
 	[NFSPROC3_SYMLINK] = {
-		.pc_func = nfsd3_proc_symlink,
-		.pc_decode = nfs3svc_decode_symlinkargs,
-		.pc_encode = nfs3svc_encode_createres,
-		.pc_release = nfs3svc_release_fhandle2,
-		.pc_argsize = sizeof(struct nfsd3_symlinkargs),
-		.pc_argzero = sizeof(struct nfsd3_symlinkargs),
-		.pc_ressize = sizeof(struct nfsd3_diropres),
-		.pc_cachetype = RC_REPLBUFF,
-		.pc_xdrressize = ST+(1+FH+pAT)+WC,
-		.pc_name = "SYMLINK",
+		.pc_func	= nfsd3_proc_symlink,
+		.pc_decode	= nfs_svc_decode_SYMLINK3args,
+		.pc_encode	= nfs_svc_encode_SYMLINK3res,
+		.pc_argsize	= sizeof(struct SYMLINK3args_wrapper),
+		.pc_argzero	= 0,
+		.pc_ressize	= sizeof(struct SYMLINK3res_wrapper),
+		.pc_cachetype	= RC_REPLBUFF,
+		.pc_xdrressize	= NFS3_SYMLINK3res_sz,
+		.pc_name	= "SYMLINK",
 	},
 	[NFSPROC3_MKNOD] = {
 		.pc_func = nfsd3_proc_mknod,
@@ -1738,9 +1789,10 @@ union nfsd3_xdrstore {
 	struct CREATE3res_wrapper	createres;
 	struct MKDIR3args_wrapper	mkdirargs;
 	struct MKDIR3res_wrapper	mkdirres;
+	struct SYMLINK3args_wrapper	symlinkargs;
+	struct SYMLINK3res_wrapper	symlinkres;
 	struct nfsd3_renameargs		renameargs;
 	struct nfsd3_linkargs		linkargs;
-	struct nfsd3_symlinkargs	symlinkargs;
 	struct nfsd3_readdirargs	readdirargs;
 	struct nfsd3_diropres 		diropres;
 	struct READLINK3res		readlinkres;
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 67cf76c13636..68f00ff604be 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -490,25 +490,6 @@ nfs3svc_decode_diropargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
 	return svcxdr_decode_diropargs3(xdr, &args->fh, &args->name, &args->len);
 }
 
-bool
-nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
-{
-	struct nfsd3_symlinkargs *args = rqstp->rq_argp;
-	struct kvec *head = rqstp->rq_arg.head;
-
-	if (!svcxdr_decode_diropargs3(xdr, &args->ffh, &args->fname, &args->flen))
-		return false;
-	if (!svcxdr_decode_sattr3(rqstp, xdr, &args->attrs))
-		return false;
-	if (xdr_stream_decode_u32(xdr, &args->tlen) < 0)
-		return false;
-
-	/* symlink_data */
-	args->first.iov_len = head->iov_len - xdr_stream_pos(xdr);
-	args->first.iov_base = xdr_inline_decode(xdr, args->tlen);
-	return args->first.iov_base != NULL;
-}
-
 bool
 nfs3svc_decode_mknodargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
 {
diff --git a/fs/nfsd/nfs3xdr_gen.c b/fs/nfsd/nfs3xdr_gen.c
index 159aff1a8567..3667c160e789 100644
--- a/fs/nfsd/nfs3xdr_gen.c
+++ b/fs/nfsd/nfs3xdr_gen.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 // Generated by xdrgen. Manual edits will be lost.
 // XDR specification file: Documentation/sunrpc/xdr/nfs3.x
-// XDR specification modification time: Tue Jul 14 11:43:26 2026
+// XDR specification modification time: Tue Jul 14 12:13:57 2026
 
 #include <linux/sunrpc/svc.h>
 
@@ -915,7 +915,7 @@ xdrgen_decode_symlinkdata3(struct xdr_stream *xdr, struct symlinkdata3 *ptr)
 {
 	if (!xdrgen_decode_sattr3(xdr, &ptr->symlink_attributes))
 		return false;
-	if (!xdrgen_decode_nfspath3(xdr, &ptr->symlink_data))
+	if (!svcxdr_decode_opaque_payload(xdr, &ptr->symlink_data, 0))
 		return false;
 	return true;
 }
@@ -2748,7 +2748,7 @@ xdrgen_encode_symlinkdata3(struct xdr_stream *xdr, const struct symlinkdata3 *va
 {
 	if (!xdrgen_encode_sattr3(xdr, &value->symlink_attributes))
 		return false;
-	if (!xdrgen_encode_nfspath3(xdr, value->symlink_data))
+	if (!svcxdr_encode_opaque_payload(xdr, value->symlink_data.len))
 		return false;
 	return true;
 }
diff --git a/fs/nfsd/nfs3xdr_gen.h b/fs/nfsd/nfs3xdr_gen.h
index 98e29c8efc5e..f336ffa92a7a 100644
--- a/fs/nfsd/nfs3xdr_gen.h
+++ b/fs/nfsd/nfs3xdr_gen.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /* Generated by xdrgen. Manual edits will be lost. */
 /* XDR specification file: Documentation/sunrpc/xdr/nfs3.x */
-/* XDR specification modification time: Tue Jul 14 11:43:26 2026 */
+/* XDR specification modification time: Tue Jul 14 12:13:57 2026 */
 
 #ifndef _LINUX_XDRGEN_NFS3_DECL_H
 #define _LINUX_XDRGEN_NFS3_DECL_H
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 1f74008bc06a..39e5caa8e286 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -968,28 +968,6 @@ static __be32 nfsd_proc_link(struct svc_rqst *rqstp)
 	return rpc_success;
 }
 
-static char *nfsd_symlink_target(const struct xdr_buf *to)
-{
-	char *result;
-
-	result = kmalloc(to->len + 1, GFP_KERNEL);
-	if (!result)
-		return ERR_PTR(-ESERVERFAULT);
-	/* The target can span the receive buffer's head, pages, and tail */
-	if (read_bytes_from_xdr_buf(to, 0, result, to->len)) {
-		kfree(result);
-		return ERR_PTR(-ESERVERFAULT);
-	}
-	result[to->len] = '\0';
-
-	/* The VFS rejects a pathname that contains a NUL byte */
-	if (strlen(result) != to->len) {
-		kfree(result);
-		return ERR_PTR(-EINVAL);
-	}
-	return result;
-}
-
 /**
  * nfsd_proc_symlink - SYMLINK: Create a symbolic link
  * @rqstp: RPC transaction context
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index c753d3257f1e..f4069da85372 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1953,6 +1953,35 @@ nfsd_readlink(struct svc_rqst *rqstp, struct svc_fh *fhp, char *buf, int *lenp)
 	return 0;
 }
 
+/**
+ * nfsd_symlink_target - Copy a SYMLINK target out of the receive buffer
+ * @to: subsegment of the receive buffer that holds the target pathname
+ *
+ * Return: a NUL-terminated pathname the caller frees with kfree(),
+ * or an ERR_PTR holding a negative errno.
+ */
+char *nfsd_symlink_target(const struct xdr_buf *to)
+{
+	char *result;
+
+	result = kmalloc(to->len + 1, GFP_KERNEL);
+	if (!result)
+		return ERR_PTR(-ESERVERFAULT);
+	/* The target can span the receive buffer's head, pages, and tail */
+	if (read_bytes_from_xdr_buf(to, 0, result, to->len)) {
+		kfree(result);
+		return ERR_PTR(-ESERVERFAULT);
+	}
+	result[to->len] = '\0';
+
+	/* The VFS rejects a pathname that contains a NUL byte */
+	if (strlen(result) != to->len) {
+		kfree(result);
+		return ERR_PTR(-EINVAL);
+	}
+	return result;
+}
+
 /**
  * nfsd_symlink - Create a symlink and look up its inode
  * @rqstp: RPC transaction being executed
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 8c130473aa79..eb75e4c82318 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -197,6 +197,7 @@ __be32		nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
 				__be32 *verf);
 __be32		nfsd_readlink(struct svc_rqst *, struct svc_fh *,
 				char *, int *);
+char		*nfsd_symlink_target(const struct xdr_buf *to);
 __be32		nfsd_symlink(struct svc_rqst *, struct svc_fh *,
 			     char *name, int len, char *path,
 			     struct nfsd_attrs *attrs,
diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
index c8d22a1be9d6..43ded5cff892 100644
--- a/fs/nfsd/xdr3.h
+++ b/fs/nfsd/xdr3.h
@@ -55,16 +55,6 @@ struct nfsd3_linkargs {
 	unsigned int		tlen;
 };
 
-struct nfsd3_symlinkargs {
-	struct svc_fh		ffh;
-	char *			fname;
-	unsigned int		flen;
-	char *			tname;
-	unsigned int		tlen;
-	struct iattr		attrs;
-	struct kvec		first;
-};
-
 struct nfsd3_readdirargs {
 	struct svc_fh		fh;
 	__u64			cookie;
@@ -201,7 +191,6 @@ bool nfs3svc_decode_diropargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_decode_mknodargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_decode_renameargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_decode_linkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
-bool nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_decode_readdirargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_decode_readdirplusargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
 bool nfs3svc_decode_commitargs(struct svc_rqst *rqstp, struct xdr_stream *xdr);
diff --git a/include/linux/sunrpc/xdrgen/nfs3.h b/include/linux/sunrpc/xdrgen/nfs3.h
index 3b6738c0074b..3e24abb1d2e5 100644
--- a/include/linux/sunrpc/xdrgen/nfs3.h
+++ b/include/linux/sunrpc/xdrgen/nfs3.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /* Generated by xdrgen. Manual edits will be lost. */
 /* XDR specification file: Documentation/sunrpc/xdr/nfs3.x */
-/* XDR specification modification time: Tue Jul 14 11:43:26 2026 */
+/* XDR specification modification time: Tue Jul 14 12:13:57 2026 */
 
 #ifndef _LINUX_XDRGEN_NFS3_DEF_H
 #define _LINUX_XDRGEN_NFS3_DEF_H
@@ -468,7 +468,7 @@ struct MKDIR3res {
 
 struct symlinkdata3 {
 	struct sattr3 symlink_attributes;
-	nfspath3 symlink_data;
+	struct xdr_buf symlink_data;
 };
 
 struct SYMLINK3args {
-- 
2.55.0