[PATCH 11/14] nfsd: add user xattr RPC XDR encoding/decoding logic

Frank van der Linden
2020-03-11T20:00:03Z

Add functions to calculate the reply size for the user extended attribute
operations, and implement the XDR encode / decode logic for these
operations.

Signed-off-by: Frank van der Linden <fllinden@amazon.com>
---
fs/nfsd/nfs4proc.c | 36 +++++
fs/nfsd/nfs4xdr.c | 448 +++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 484 insertions(+)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index a76b9025a357..44d488bdebd9 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2778,6 +2778,42 @@ static inline u32 nfsd4_seek_rsize(struct svc_rqst *rqstp, struct nfsd4_op *op)
return (op_encode_hdr_size + 3) * sizeof(__be32);
}

+static inline u32 nfsd4_getxattr_rsize(struct svc_rqst *rqstp,
+ struct nfsd4_op *op)
+{
+ u32 maxcount, rlen;
+
+ maxcount = svc_max_payload(rqstp);
+ rlen = min_t(u32, XATTR_SIZE_MAX, maxcount);
+
+ return (op_encode_hdr_size + 1 + XDR_QUADLEN(rlen)) * sizeof(__be32);
+}
+
+static inline u32 nfsd4_setxattr_rsize(struct svc_rqst *rqstp,
+ struct nfsd4_op *op)
+{
+ return (op_encode_hdr_size + op_encode_change_info_maxsz)
+ * sizeof(__be32);
+}
+static inline u32 nfsd4_listxattrs_rsize(struct svc_rqst *rqstp,
+ struct nfsd4_op *op)
+{
+ u32 maxcount, rlen;
+
+ maxcount = svc_max_payload(rqstp);
+ rlen = min(op->u.listxattrs.lsxa_maxcount, maxcount);
+
+ return (op_encode_hdr_size + 4 + XDR_QUADLEN(rlen)) * sizeof(__be32);
+}
+
+static inline u32 nfsd4_removexattr_rsize(struct svc_rqst *rqstp,
+ struct nfsd4_op *op)
+{
+ return (op_encode_hdr_size + op_encode_change_info_maxsz)
+ * sizeof(__be32);
+}
+
+
static const struct nfsd4_operation nfsd4_ops[LAST_NFS4_OP + 1] = {
[OP_ACCESS] = {
.op_func = nfsd4_access,
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index b12d7ac6f52c..41c8b95ca1c5 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1879,6 +1879,224 @@ nfsd4_decode_seek(struct nfsd4_compoundargs *argp, struct nfsd4_seek *seek)
DECODE_TAIL;
}

+/*
+ * XDR data that is more than PAGE_SIZE in size is normally part of a
+ * read or write. However, the size of extended attributes is limited
+ * by the maximum request size, and then further limited by the underlying
+ * filesystem limits. This can exceed PAGE_SIZE (currently, XATTR_SIZE_MAX
+ * is 64k). Since there is no kvec- or page-based interface to xattrs,
+ * and we're not dealing with contiguous pages, we need to do some copying.
+ */
+
+/*
+ * Decode int to buffer. Uses head and pages constructed by
+ * svcxdr_construct_vector.
+ */
+static int
+nfsd4_vbuf_from_stream(struct nfsd4_compoundargs *argp, struct kvec *head,
+ struct page **pages, char **bufp, u32 buflen)
+{
+ char *tmp, *dp;
+ u32 len;
+
+ if (buflen <= head->iov_len) {
+ /*
+ * We're in luck, the head has enough space. Just return
+ * the head, no need for copying.
+ */
+ *bufp = head->iov_base;
+ return 0;
+ }
+
+ tmp = svcxdr_tmpalloc(argp, buflen);
+ if (tmp == NULL)
+ return nfserr_jukebox;
+
+ dp = tmp;
+ memcpy(dp, head->iov_base, head->iov_len);
+ buflen -= head->iov_len;
+ dp += head->iov_len;
+
+ while (buflen > 0) {
+ len = min_t(u32, buflen, PAGE_SIZE);
+ memcpy(dp, page_address(*pages), len);
+
+ buflen -= len;
+ dp += len;
+ pages++;
+ }
+
+ *bufp = tmp;
+ return 0;
+}
+
+/*
+ * Get a user extended attribute name from the XDR buffer.
+ * It will not have the "user." prefix, so prepend it.
+ * Lastly, check for nul characters in the name.
+ */
+static int
+nfsd4_decode_xattr_name(struct nfsd4_compoundargs *argp, char **namep)
+{
+ DECODE_HEAD;
+ char *name, *sp, *dp;
+ u32 namelen, cnt;
+
+ READ_BUF(4);
+ namelen = be32_to_cpup(p++);
+
+ if (namelen > (XATTR_NAME_MAX - XATTR_USER_PREFIX_LEN))
+ return nfserr_nametoolong;
+
+ if (namelen == 0)
+ goto xdr_error;
+
+ READ_BUF(namelen);
+
+ name = svcxdr_tmpalloc(argp, namelen + XATTR_USER_PREFIX_LEN + 1);
+ if (!name)
+ return nfserr_jukebox;
+
+ memcpy(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
+
+ /*
+ * Copy the extended attribute name over while checking for 0
+ * characters.
+ */
+ sp = (char *)p;
+ dp = name + XATTR_USER_PREFIX_LEN;
+ cnt = namelen;
+
+ while (cnt-- > 0) {
+ if (*sp == '\0')
+ goto xdr_error;
+ *dp++ = *sp++;
+ }
+ *dp = '\0';
+
+ *namep = name;
+
+ DECODE_TAIL;
+}
+
+/*
+ * A GETXATTR op request comes without a length specifier. We just set the
+ * maximum length for the reply based on XATTR_SIZE_MAX and the maximum
+ * channel reply size, allocate a buffer of that length and pass it to
+ * vfs_getxattr.
+ */
+static __be32
+nfsd4_decode_getxattr(struct nfsd4_compoundargs *argp,
+ struct nfsd4_getxattr *getxattr)
+{
+ int status;
+ u32 maxcount;
+
+ status = nfsd4_decode_xattr_name(argp, &getxattr->getxa_name);
+ if (status)
+ return status;
+
+ maxcount = svc_max_payload(argp->rqstp);
+ maxcount = min_t(u32, XATTR_SIZE_MAX, maxcount);
+
+ getxattr->getxa_buf = svcxdr_tmpalloc(argp, maxcount);
+ if (!getxattr->getxa_buf)
+ status = nfserr_jukebox;
+ getxattr->getxa_len = maxcount;
+
+ return status;
+}
+
+static __be32
+nfsd4_decode_setxattr(struct nfsd4_compoundargs *argp,
+ struct nfsd4_setxattr *setxattr)
+{
+ DECODE_HEAD;
+ u32 flags, maxcount, size;
+ struct kvec head;
+ struct page **pagelist;
+
+ READ_BUF(4);
+ flags = be32_to_cpup(p++);
+
+ if (flags > SETXATTR4_REPLACE)
+ return nfserr_inval;
+ setxattr->setxa_flags = flags;
+
+ status = nfsd4_decode_xattr_name(argp, &setxattr->setxa_name);
+ if (status)
+ return status;
+
+ maxcount = svc_max_payload(argp->rqstp);
+ maxcount = min_t(u32, XATTR_SIZE_MAX, maxcount);
+
+ READ_BUF(4);
+ size = be32_to_cpup(p++);
+ if (size > maxcount)
+ return nfserr_xattr2big;
+
+ setxattr->setxa_len = size;
+ if (size > 0) {
+ status = svcxdr_construct_vector(argp, &head, &pagelist, size);
+ if (status)
+ return status;
+
+ status = nfsd4_vbuf_from_stream(argp, &head, pagelist,
+ &setxattr->setxa_buf, size);
+ }
+
+ DECODE_TAIL;
+}
+
+static __be32
+nfsd4_decode_listxattrs(struct nfsd4_compoundargs *argp,
+ struct nfsd4_listxattrs *listxattrs)
+{
+ DECODE_HEAD;
+ u32 maxcount;
+
+ READ_BUF(12);
+ p = xdr_decode_hyper(p, &listxattrs->lsxa_cookie);
+
+ /*
+ * If the cookie is too large to have even one user.x attribute
+ * plus trailing '\0' left in a maximum size buffer, it's invalid.
+ */
+ if (listxattrs->lsxa_cookie >=
+ (XATTR_LIST_MAX / (XATTR_USER_PREFIX_LEN + 2)))
+ return nfserr_badcookie;
+
+ maxcount = be32_to_cpup(p++);
+ if (maxcount < 8)
+ /* Always need at least 2 words (length and one character) */
+ return nfserr_inval;
+
+ maxcount = min(maxcount, svc_max_payload(argp->rqstp));
+ listxattrs->lsxa_maxcount = maxcount;
+
+ /*
+ * Unfortunately, there is no interface to only list xattrs for
+ * one prefix. So there is no good way to convert maxcount to
+ * a maximum value to pass to vfs_listxattr, as we don't know
+ * how many of the returned attributes will be user attributes.
+ *
+ * So, always ask vfs_listxattr for the maximum size, and encode
+ * as many as possible.
+ */
+ listxattrs->lsxa_buf = svcxdr_tmpalloc(argp, XATTR_LIST_MAX);
+ if (!listxattrs->lsxa_buf)
+ status = nfserr_jukebox;
+
+ DECODE_TAIL;
+}
+
+static __be32
+nfsd4_decode_removexattr(struct nfsd4_compoundargs *argp,
+ struct nfsd4_removexattr *removexattr)
+{
+ return nfsd4_decode_xattr_name(argp, &removexattr->rmxa_name);
+}
+
static __be32
nfsd4_decode_noop(struct nfsd4_compoundargs *argp, void *p)
{
@@ -1975,6 +2193,11 @@ static const nfsd4_dec nfsd4_dec_ops[] = {
[OP_SEEK] = (nfsd4_dec)nfsd4_decode_seek,
[OP_WRITE_SAME] = (nfsd4_dec)nfsd4_decode_notsupp,
[OP_CLONE] = (nfsd4_dec)nfsd4_decode_clone,
+ /* RFC 8276 extended atributes operations */
+ [OP_GETXATTR] = (nfsd4_dec)nfsd4_decode_getxattr,
+ [OP_SETXATTR] = (nfsd4_dec)nfsd4_decode_setxattr,
+ [OP_LISTXATTRS] = (nfsd4_dec)nfsd4_decode_listxattrs,
+ [OP_REMOVEXATTR] = (nfsd4_dec)nfsd4_decode_removexattr,
};

static inline bool
@@ -4458,6 +4681,225 @@ nfsd4_encode_noop(struct nfsd4_compoundres *resp, __be32 nfserr, void *p)
return nfserr;
}

+/*
+ * Encode kmalloc-ed buffer in to XDR stream.
+ */
+static int
+nfsd4_vbuf_to_stream(struct xdr_stream *xdr, char *buf, u32 buflen)
+{
+ u32 cplen;
+ __be32 *p;
+
+ cplen = min_t(unsigned long, buflen,
+ ((void *)xdr->end - (void *)xdr->p));
+ p = xdr_reserve_space(xdr, cplen);
+ if (!p)
+ return nfserr_resource;
+
+ memcpy(p, buf, cplen);
+ buf += cplen;
+ buflen -= cplen;
+
+ while (buflen) {
+ cplen = min_t(u32, buflen, PAGE_SIZE);
+ p = xdr_reserve_space(xdr, cplen);
+ if (!p)
+ return nfserr_resource;
+
+ memcpy(p, buf, cplen);
+
+ if (cplen < PAGE_SIZE) {
+ /*
+ * We're done, with a length that wasn't page
+ * aligned, so possibly not word aligned. Pad
+ * any trailing bytes with 0.
+ */
+ xdr_encode_opaque_fixed(p, NULL, cplen);
+ break;
+ }
+
+ buflen -= PAGE_SIZE;
+ buf += PAGE_SIZE;
+ }
+
+ return 0;
+}
+
+static __be32
+nfsd4_encode_getxattr(struct nfsd4_compoundres *resp, __be32 nfserr,
+ struct nfsd4_getxattr *getxattr)
+{
+ struct xdr_stream *xdr = &resp->xdr;
+ __be32 *p;
+
+ p = xdr_reserve_space(xdr, 4);
+ if (!p)
+ return nfserr_resource;
+
+ *p = cpu_to_be32(getxattr->getxa_len);
+
+ if (getxattr->getxa_len == 0)
+ return 0;
+
+ return nfsd4_vbuf_to_stream(xdr, getxattr->getxa_buf,
+ getxattr->getxa_len);
+}
+
+static __be32
+nfsd4_encode_setxattr(struct nfsd4_compoundres *resp, __be32 nfserr,
+ struct nfsd4_setxattr *setxattr)
+{
+ struct xdr_stream *xdr = &resp->xdr;
+ __be32 *p;
+
+ p = xdr_reserve_space(xdr, 20);
+ if (!p)
+ return nfserr_resource;
+
+ encode_cinfo(p, &setxattr->setxa_cinfo);
+
+ return 0;
+}
+
+/*
+ * See if there are cookie values that can be rejected outright.
+ */
+static int
+nfsd4_listxattr_validate_cookie(struct nfsd4_listxattrs *listxattrs,
+ u32 *offsetp)
+{
+ u64 cookie = listxattrs->lsxa_cookie;
+
+ /*
+ * If the cookie is larger than the maximum number we can fit
+ * in either the buffer we just got back from vfs_listxattr, or,
+ * XDR-encoded, in the return buffer, it's invalid.
+ */
+ if (cookie > (listxattrs->lsxa_len) / (XATTR_USER_PREFIX_LEN + 2))
+ return nfserr_badcookie;
+
+ if (cookie > (listxattrs->lsxa_maxcount /
+ (XDR_QUADLEN(XATTR_USER_PREFIX_LEN + 2) + 4)))
+ return nfserr_badcookie;
+
+ *offsetp = (u32)cookie;
+ return 0;
+}
+
+static __be32
+nfsd4_encode_listxattrs(struct nfsd4_compoundres *resp, __be32 nfserr,
+ struct nfsd4_listxattrs *listxattrs)
+{
+ struct xdr_stream *xdr = &resp->xdr;
+ u32 cookie_offset, count_offset, eof;
+ u32 left, xdrleft, slen, count;
+ u32 xdrlen, offset;
+ u64 cookie;
+ char *sp;
+ int status;
+ __be32 *p;
+ u32 nuser;
+
+ eof = 1;
+
+ status = nfsd4_listxattr_validate_cookie(listxattrs, &offset);
+ if (status)
+ return status;
+
+ /*
+ * Reserve space for the cookie and the name array count. Record
+ * the offsets to save them later.
+ */
+ cookie_offset = xdr->buf->len;
+ count_offset = cookie_offset + 8;
+ p = xdr_reserve_space(xdr, 12);
+ if (!p)
+ return nfserr_resource;
+
+ count = 0;
+ left = listxattrs->lsxa_len;
+ sp = listxattrs->lsxa_buf;
+ nuser = 0;
+
+ xdrleft = listxattrs->lsxa_maxcount;
+
+ while (left > 0 && xdrleft > 0) {
+ slen = strlen(sp);
+
+ /*
+ * Check if this a user. attribute, skip it if not.
+ */
+ if (strncmp(sp, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
+ goto contloop;
+
+ slen -= XATTR_USER_PREFIX_LEN;
+ xdrlen = 4 + ((slen + 3) & ~3);
+ if (xdrlen > xdrleft) {
+ if (count == 0) {
+ /*
+ * Can't even fit the first attribute name.
+ */
+ return nfserr_toosmall;
+ }
+ eof = 0;
+ goto wreof;
+ }
+
+ left -= XATTR_USER_PREFIX_LEN;
+ sp += XATTR_USER_PREFIX_LEN;
+ if (nuser++ < offset)
+ goto contloop;
+
+
+ p = xdr_reserve_space(xdr, xdrlen);
+ if (!p)
+ return nfserr_resource;
+
+ p = xdr_encode_opaque(p, sp, slen);
+
+ xdrleft -= xdrlen;
+ count++;
+contloop:
+ sp += slen + 1;
+ left -= slen + 1;
+ }
+
+ /*
+ * If there were user attributes to copy, but we didn't copy
+ * any, the offset was too large (e.g. the cookie was invalid).
+ */
+ if (nuser > 0 && count == 0)
+ return nfserr_badcookie;
+
+wreof:
+ p = xdr_reserve_space(xdr, 4);
+ if (!p)
+ return nfserr_resource;
+ *p = cpu_to_be32(eof);
+
+ cookie = offset + count;
+
+ write_bytes_to_xdr_buf(xdr->buf, cookie_offset, &cookie, 8);
+ count = htonl(count);
+ write_bytes_to_xdr_buf(xdr->buf, count_offset, &count, 4);
+ return 0;
+}
+
+static __be32
+nfsd4_encode_removexattr(struct nfsd4_compoundres *resp, __be32 nfserr,
+ struct nfsd4_removexattr *removexattr)
+{
+ struct xdr_stream *xdr = &resp->xdr;
+ __be32 *p;
+
+ p = xdr_reserve_space(xdr, 20);
+ if (!p)
+ return nfserr_resource;
+
+ p = encode_cinfo(p, &removexattr->rmxa_cinfo);
+ return 0;
+}
+
typedef __be32(* nfsd4_enc)(struct nfsd4_compoundres *, __be32, void *);

/*
@@ -4547,6 +4989,12 @@ static const nfsd4_enc nfsd4_enc_ops[] = {
[OP_SEEK] = (nfsd4_enc)nfsd4_encode_seek,
[OP_WRITE_SAME] = (nfsd4_enc)nfsd4_encode_noop,
[OP_CLONE] = (nfsd4_enc)nfsd4_encode_noop,
+
+ /* RFC 8276 extended atributes operations */
+ [OP_GETXATTR] = (nfsd4_enc)nfsd4_encode_getxattr,
+ [OP_SETXATTR] = (nfsd4_enc)nfsd4_encode_setxattr,
+ [OP_LISTXATTRS] = (nfsd4_enc)nfsd4_encode_listxattrs,
+ [OP_REMOVEXATTR] = (nfsd4_enc)nfsd4_encode_removexattr,
};

/*
--
2.16.6