NFSv4.2: define limits and sizes for user xattr handling

Set limits for extended attributes (attribute value size and listxattr
buffer size), based on the fs-independent limits (XATTR_*_MAX).

Define the maximum XDR sizes for the RFC 8276 XATTR operations.
In the case of operations that carry a larger payload (SETXATTR,
GETXATTR, LISTXATTR), these exclude that payload, which is added
as separate pages, like other operations do.

Define, much like for read and write operations, the maximum overhead
sizes for get/set/listxattr, and use them to limit the maximum payload
size for those operations, in combination with the channel attributes.

Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 74 insertions, 0 deletions

diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c
index c03f3246d6c5..6712daa9d85b 100644
--- a/fs/nfs/nfs42xdr.c
+++ b/fs/nfs/nfs42xdr.c
@@ -169,6 +169,80 @@
 					 decode_clone_maxsz + \
 					 decode_getattr_maxsz)
 
+#ifdef CONFIG_NFS_V4_2
+/* Not limited by NFS itself, limited by the generic xattr code */
+#define nfs4_xattr_name_maxsz   XDR_QUADLEN(XATTR_NAME_MAX)
+
+#define encode_getxattr_maxsz   (op_encode_hdr_maxsz + 1 + \
+				 nfs4_xattr_name_maxsz)
+#define decode_getxattr_maxsz   (op_decode_hdr_maxsz + 1 + 1)
+#define encode_setxattr_maxsz   (op_encode_hdr_maxsz + \
+				 1 + nfs4_xattr_name_maxsz + 1)
+#define decode_setxattr_maxsz   (op_decode_hdr_maxsz + decode_change_info_maxsz)
+#define encode_listxattrs_maxsz  (op_encode_hdr_maxsz + 2 + 1)
+#define decode_listxattrs_maxsz  (op_decode_hdr_maxsz + 2 + 1 + 1)
+#define encode_removexattr_maxsz (op_encode_hdr_maxsz + 1 + \
+				  nfs4_xattr_name_maxsz)
+#define decode_removexattr_maxsz (op_decode_hdr_maxsz + \
+				  decode_change_info_maxsz)
+
+#define NFS4_enc_getxattr_sz	(compound_encode_hdr_maxsz + \
+				encode_sequence_maxsz + \
+				encode_putfh_maxsz + \
+				encode_getxattr_maxsz)
+#define NFS4_dec_getxattr_sz	(compound_decode_hdr_maxsz + \
+				decode_sequence_maxsz + \
+				decode_putfh_maxsz + \
+				decode_getxattr_maxsz)
+#define NFS4_enc_setxattr_sz	(compound_encode_hdr_maxsz + \
+				encode_sequence_maxsz + \
+				encode_putfh_maxsz + \
+				encode_setxattr_maxsz)
+#define NFS4_dec_setxattr_sz	(compound_decode_hdr_maxsz + \
+				decode_sequence_maxsz + \
+				decode_putfh_maxsz + \
+				decode_setxattr_maxsz)
+#define NFS4_enc_listxattrs_sz	(compound_encode_hdr_maxsz + \
+				encode_sequence_maxsz + \
+				encode_putfh_maxsz + \
+				encode_listxattrs_maxsz)
+#define NFS4_dec_listxattrs_sz	(compound_decode_hdr_maxsz + \
+				decode_sequence_maxsz + \
+				decode_putfh_maxsz + \
+				decode_listxattrs_maxsz)
+#define NFS4_enc_removexattr_sz	(compound_encode_hdr_maxsz + \
+				encode_sequence_maxsz + \
+				encode_putfh_maxsz + \
+				encode_removexattr_maxsz)
+#define NFS4_dec_removexattr_sz	(compound_decode_hdr_maxsz + \
+				decode_sequence_maxsz + \
+				decode_putfh_maxsz + \
+				decode_removexattr_maxsz)
+
+/*
+ * These values specify the maximum amount of data that is not
+ * associated with the extended attribute name or extended
+ * attribute list in the SETXATTR, GETXATTR and LISTXATTR
+ * respectively.
+ */
+const u32 nfs42_maxsetxattr_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
+					compound_encode_hdr_maxsz +
+					encode_sequence_maxsz +
+					encode_putfh_maxsz + 1 +
+					nfs4_xattr_name_maxsz)
+					* XDR_UNIT);
+
+const u32 nfs42_maxgetxattr_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
+					compound_decode_hdr_maxsz +
+					decode_sequence_maxsz +
+					decode_putfh_maxsz + 1) * XDR_UNIT);
+
+const u32 nfs42_maxlistxattrs_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
+					compound_decode_hdr_maxsz +
+					decode_sequence_maxsz +
+					decode_putfh_maxsz + 3) * XDR_UNIT);
+#endif
+
 static void encode_fallocate(struct xdr_stream *xdr,
 			     const struct nfs42_falloc_args *args)
 {