> On Jan 22, 2018, at 2:00 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> On Wed, Jan 03, 2018 at 03:42:35PM -0500, Chuck Lever wrote:
>> Move common code in NFSD's symlink arg decoders into a helper. The
>> immediate benefits include:
>>
>> - one fewer data copies on transports that support DDP
>> - no memory allocation in the NFSv4 XDR decoder
>> - consistent error checking across all versions
>> - reduction of code duplication
>> - support for both legal forms of SYMLINK requests on RDMA
>> transports for all versions of NFS (in particular, NFSv2, for
>> completeness)
>>
>> In the long term, this helper is an appropriate spot to perform a
>> per-transport call-out to fill the pathname argument using, say,
>> RDMA Reads.
>>
>> Filling the pathname in the proc function also means that eventually
>> the incoming filehandle can be interpreted so that filesystem-
>> specific memory can be allocated as a sink for the pathname
>> argument, rather than using anonymous pages.
>>
>> Wondering why the current code punts a zero-length SYMLINK. Is it
>> illegal to create a zero-length SYMLINK on Linux?
>
> SYMLINK(2) says
>
> ENOENT A directory component in linkpath does not exist or is a
> dangling symbolic link, or target or linkpath is an empty
> string.
>
> That doesn't explain the INVAL, or why this is the right place to be
> checking it.
RFC 1813:
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
Interestingly, neither INVAL nor NOENT are valid
status codes for NFSv3 SYMLINK. NFS3ERR_NOTSUPP
might be closest, I suppose.
RFC 5661 says explicitly:
If the objname has a length of zero, or if objname does not obey the
UTF-8 definition, the error NFS4ERR_INVAL will be returned.
And lists these as valid status codes for CREATE(NF4LNK):
| NFS4ERR_ACCESS, NFS4ERR_ATTRNOTSUPP, |
| NFS4ERR_BADCHAR, NFS4ERR_BADNAME, |
| NFS4ERR_BADOWNER, NFS4ERR_BADTYPE, |
| NFS4ERR_BADXDR, NFS4ERR_DEADSESSION, |
| NFS4ERR_DELAY, NFS4ERR_DQUOT, |
| NFS4ERR_EXIST, NFS4ERR_FHEXPIRED, |
| NFS4ERR_INVAL, NFS4ERR_IO, NFS4ERR_MLINK, |
| NFS4ERR_MOVED, NFS4ERR_NAMETOOLONG, |
| NFS4ERR_NOFILEHANDLE, NFS4ERR_NOSPC, |
| NFS4ERR_NOTDIR, NFS4ERR_OP_NOT_IN_SESSION, |
| NFS4ERR_PERM, NFS4ERR_REP_TOO_BIG, |
| NFS4ERR_REP_TOO_BIG_TO_CACHE, |
| NFS4ERR_REQ_TOO_BIG, |
| NFS4ERR_RETRY_UNCACHED_REP, NFS4ERR_ROFS, |
| NFS4ERR_SERVERFAULT, NFS4ERR_STALE, |
| NFS4ERR_TOO_MANY_OPS, |
| NFS4ERR_UNSAFE_COMPOUND |
> I'm a little nervous about the NULL termination in
> svc_fill_symlink_pathname; how do we know it's safe to write a zero
> there? I haven't checked it carefully yet.
svc_fill_symlink_pathname grabs a whole fresh page
from @rqstp. It is safe to write bytes anywhere in
that page.
> --g.
>
>>
>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>> ---
>> fs/nfsd/nfs3proc.c | 10 +++++++
>> fs/nfsd/nfs3xdr.c | 51 ++++++++-------------------------
>> fs/nfsd/nfs4proc.c | 7 +++++
>> fs/nfsd/nfs4xdr.c | 10 +++++--
>> fs/nfsd/nfsproc.c | 14 +++++----
>> fs/nfsd/nfsxdr.c | 49 +++++++++++++++++++-------------
>> fs/nfsd/xdr.h | 1 +
>> fs/nfsd/xdr3.h | 1 +
>> fs/nfsd/xdr4.h | 2 +
>> include/linux/sunrpc/svc.h | 2 +
>> net/sunrpc/svc.c | 67 ++++++++++++++++++++++++++++++++++++++++++++
>> 11 files changed, 146 insertions(+), 68 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
>> index 2dd95eb..6259a4b 100644
>> --- a/fs/nfsd/nfs3proc.c
>> +++ b/fs/nfsd/nfs3proc.c
>> @@ -283,6 +283,16 @@
>> struct nfsd3_diropres *resp = rqstp->rq_resp;
>> __be32 nfserr;
>>
>> + if (argp->tlen == 0)
>> + RETURN_STATUS(nfserr_inval);
>> + if (argp->tlen > NFS3_MAXPATHLEN)
>> + RETURN_STATUS(nfserr_nametoolong);
>> +
>> + argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
>> + argp->tlen);
>> + if (IS_ERR(argp->tname))
>> + RETURN_STATUS(nfserrno(PTR_ERR(argp->tname)));
>> +
>> dprintk("nfsd: SYMLINK(3) %s %.*s -> %.*s\n",
>> SVCFH_fmt(&argp->ffh),
>> argp->flen, argp->fname,
>> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
>> index 240cdb0e..78b555b 100644
>> --- a/fs/nfsd/nfs3xdr.c
>> +++ b/fs/nfsd/nfs3xdr.c
>> @@ -452,51 +452,24 @@ void fill_post_wcc(struct svc_fh *fhp)
>> nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
>> {
>> struct nfsd3_symlinkargs *args = rqstp->rq_argp;
>> - unsigned int len, avail;
>> - char *old, *new;
>> - struct kvec *vec;
>> + char *base = (char *)p;
>> + size_t dlen;
>>
>> if (!(p = decode_fh(p, &args->ffh)) ||
>> - !(p = decode_filename(p, &args->fname, &args->flen))
>> - )
>> + !(p = decode_filename(p, &args->fname, &args->flen)))
>> return 0;
>> p = decode_sattr3(p, &args->attrs);
>>
>> - /* now decode the pathname, which might be larger than the first page.
>> - * As we have to check for nul's anyway, we copy it into a new page
>> - * This page appears in the rq_res.pages list, but as pages_len is always
>> - * 0, it won't get in the way
>> - */
>> - len = ntohl(*p++);
>> - if (len == 0 || len > NFS3_MAXPATHLEN || len >= PAGE_SIZE)
>> - return 0;
>> - args->tname = new = page_address(*(rqstp->rq_next_page++));
>> - args->tlen = len;
>> - /* first copy and check from the first page */
>> - old = (char*)p;
>> - vec = &rqstp->rq_arg.head[0];
>> - if ((void *)old > vec->iov_base + vec->iov_len)
>> - return 0;
>> - avail = vec->iov_len - (old - (char*)vec->iov_base);
>> - while (len && avail && *old) {
>> - *new++ = *old++;
>> - len--;
>> - avail--;
>> - }
>> - /* now copy next page if there is one */
>> - if (len && !avail && rqstp->rq_arg.page_len) {
>> - avail = min_t(unsigned int, rqstp->rq_arg.page_len, PAGE_SIZE);
>> - old = page_address(rqstp->rq_arg.pages[0]);
>> - }
>> - while (len && avail && *old) {
>> - *new++ = *old++;
>> - len--;
>> - avail--;
>> - }
>> - *new = '\0';
>> - if (len)
>> - return 0;
>> + args->tlen = ntohl(*p++);
>>
>> + args->first.iov_base = p;
>> + args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
>> + args->first.iov_len -= (char *)p - base;
>> +
>> + dlen = args->first.iov_len + rqstp->rq_arg.page_len +
>> + rqstp->rq_arg.tail[0].iov_len;
>> + if (dlen < XDR_QUADLEN(args->tlen) << 2)
>> + return 0;
>> return 1;
>> }
>>
>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
>> index 5029b96..36bd1f7 100644
>> --- a/fs/nfsd/nfs4proc.c
>> +++ b/fs/nfsd/nfs4proc.c
>> @@ -605,6 +605,13 @@ static void gen_boot_verifier(nfs4_verifier *verifier, struct net *net)
>>
>> switch (create->cr_type) {
>> case NF4LNK:
>> + if (create->cr_datalen > NFS4_MAXPATHLEN)
>> + return nfserr_nametoolong;
>> + create->cr_data =
>> + svc_fill_symlink_pathname(rqstp, &create->cr_first,
>> + create->cr_datalen);
>> + if (IS_ERR(create->cr_data))
>> + return nfserrno(PTR_ERR(create->cr_data));
>> status = nfsd_symlink(rqstp, &cstate->current_fh,
>> create->cr_name, create->cr_namelen,
>> create->cr_data, &resfh);
>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>> index bd25230..d05384e 100644
>> --- a/fs/nfsd/nfs4xdr.c
>> +++ b/fs/nfsd/nfs4xdr.c
>> @@ -648,6 +648,7 @@ static __be32 nfsd4_decode_bind_conn_to_session(struct nfsd4_compoundargs *argp,
>> static __be32
>> nfsd4_decode_create(struct nfsd4_compoundargs *argp, struct nfsd4_create *create)
>> {
>> + struct kvec *head;
>> DECODE_HEAD;
>>
>> READ_BUF(4);
>> @@ -656,10 +657,13 @@ static __be32 nfsd4_decode_bind_conn_to_session(struct nfsd4_compoundargs *argp,
>> case NF4LNK:
>> READ_BUF(4);
>> create->cr_datalen = be32_to_cpup(p++);
>> + if (create->cr_datalen == 0)
>> + return nfserr_inval;
>> + head = argp->rqstp->rq_arg.head;
>> + create->cr_first.iov_base = p;
>> + create->cr_first.iov_len = head->iov_len;
>> + create->cr_first.iov_len -= (char *)p - (char *)head->iov_base;
>> READ_BUF(create->cr_datalen);
>> - create->cr_data = svcxdr_dupstr(argp, p, create->cr_datalen);
>> - if (!create->cr_data)
>> - return nfserr_jukebox;
>> break;
>> case NF4BLK:
>> case NF4CHR:
>> diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
>> index 1995ea6..f107f9f 100644
>> --- a/fs/nfsd/nfsproc.c
>> +++ b/fs/nfsd/nfsproc.c
>> @@ -449,17 +449,19 @@
>> struct svc_fh newfh;
>> __be32 nfserr;
>>
>> + if (argp->tlen > NFS_MAXPATHLEN)
>> + return nfserr_nametoolong;
>> +
>> + argp->tname = svc_fill_symlink_pathname(rqstp, &argp->first,
>> + argp->tlen);
>> + if (IS_ERR(argp->tname))
>> + return nfserrno(PTR_ERR(argp->tname));
>> +
>> dprintk("nfsd: SYMLINK %s %.*s -> %.*s\n",
>> SVCFH_fmt(&argp->ffh), argp->flen, argp->fname,
>> argp->tlen, argp->tname);
>>
>> fh_init(&newfh, NFS_FHSIZE);
>> - /*
>> - * Crazy hack: the request fits in a page, and already-decoded
>> - * attributes follow argp->tname, so it's safe to just write a
>> - * null to ensure it's null-terminated:
>> - */
>> - argp->tname[argp->tlen] = '\0';
>> nfserr = nfsd_symlink(rqstp, &argp->ffh, argp->fname, argp->flen,
>> argp->tname, &newfh);
>>
>> diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
>> index 165e25e..8fcd047 100644
>> --- a/fs/nfsd/nfsxdr.c
>> +++ b/fs/nfsd/nfsxdr.c
>> @@ -71,22 +71,6 @@ __be32 *nfs2svc_decode_fh(__be32 *p, struct svc_fh *fhp)
>> }
>>
>> static __be32 *
>> -decode_pathname(__be32 *p, char **namp, unsigned int *lenp)
>> -{
>> - char *name;
>> - unsigned int i;
>> -
>> - if ((p = xdr_decode_string_inplace(p, namp, lenp, NFS_MAXPATHLEN)) != NULL) {
>> - for (i = 0, name = *namp; i < *lenp; i++, name++) {
>> - if (*name == '\0')
>> - return NULL;
>> - }
>> - }
>> -
>> - return p;
>> -}
>> -
>> -static __be32 *
>> decode_sattr(__be32 *p, struct iattr *iap)
>> {
>> u32 tmp, tmp1;
>> @@ -383,14 +367,39 @@ __be32 *nfs2svc_encode_fattr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *f
>> nfssvc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
>> {
>> struct nfsd_symlinkargs *args = rqstp->rq_argp;
>> + char *base = (char *)p;
>> + size_t xdrlen;
>>
>> if ( !(p = decode_fh(p, &args->ffh))
>> - || !(p = decode_filename(p, &args->fname, &args->flen))
>> - || !(p = decode_pathname(p, &args->tname, &args->tlen)))
>> + || !(p = decode_filename(p, &args->fname, &args->flen)))
>> return 0;
>> - p = decode_sattr(p, &args->attrs);
>>
>> - return xdr_argsize_check(rqstp, p);
>> + args->tlen = ntohl(*p++);
>> + if (args->tlen == 0)
>> + return 0;
>> +
>> + args->first.iov_base = p;
>> + args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
>> + args->first.iov_len -= (char *)p - base;
>> +
>> + /* This request is never larger than a page. Therefore,
>> + * transport will deliver either:
>> + * 1. pathname in the pagelist -> sattr is in the tail.
>> + * 2. everything in the head buffer -> sattr is in the head.
>> + */
>> + if (rqstp->rq_arg.page_len) {
>> + if (args->tlen != rqstp->rq_arg.page_len)
>> + return 0;
>> + p = rqstp->rq_arg.tail[0].iov_base;
>> + } else {
>> + xdrlen = XDR_QUADLEN(args->tlen);
>> + if (xdrlen > args->first.iov_len - (8 * sizeof(__be32)))
>> + return 0;
>> + p += xdrlen;
>> + }
>> + decode_sattr(p, &args->attrs);
>> +
>> + return 1;
>> }
>>
>> int
>> diff --git a/fs/nfsd/xdr.h b/fs/nfsd/xdr.h
>> index a765c41..ea7cca3 100644
>> --- a/fs/nfsd/xdr.h
>> +++ b/fs/nfsd/xdr.h
>> @@ -72,6 +72,7 @@ struct nfsd_symlinkargs {
>> char * tname;
>> unsigned int tlen;
>> struct iattr attrs;
>> + struct kvec first;
>> };
>>
>> struct nfsd_readdirargs {
>> diff --git a/fs/nfsd/xdr3.h b/fs/nfsd/xdr3.h
>> index deccf7f..2cb29e9 100644
>> --- a/fs/nfsd/xdr3.h
>> +++ b/fs/nfsd/xdr3.h
>> @@ -90,6 +90,7 @@ struct nfsd3_symlinkargs {
>> char * tname;
>> unsigned int tlen;
>> struct iattr attrs;
>> + struct kvec first;
>> };
>>
>> struct nfsd3_readdirargs {
>> diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
>> index d56219d..b485cd1 100644
>> --- a/fs/nfsd/xdr4.h
>> +++ b/fs/nfsd/xdr4.h
>> @@ -110,6 +110,7 @@ struct nfsd4_create {
>> struct {
>> u32 datalen;
>> char *data;
>> + struct kvec first;
>> } link; /* NF4LNK */
>> struct {
>> u32 specdata1;
>> @@ -124,6 +125,7 @@ struct nfsd4_create {
>> };
>> #define cr_datalen u.link.datalen
>> #define cr_data u.link.data
>> +#define cr_first u.link.first
>> #define cr_specdata1 u.dev.specdata1
>> #define cr_specdata2 u.dev.specdata2
>>
>> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
>> index 238b9ae..fd5846e 100644
>> --- a/include/linux/sunrpc/svc.h
>> +++ b/include/linux/sunrpc/svc.h
>> @@ -495,6 +495,8 @@ int svc_register(const struct svc_serv *, struct net *, const int,
>> char * svc_print_addr(struct svc_rqst *, char *, size_t);
>> unsigned int svc_fill_write_vector(struct svc_rqst *rqstp,
>> struct kvec *first, size_t total);
>> +char *svc_fill_symlink_pathname(struct svc_rqst *rqstp,
>> + struct kvec *first, size_t total);
>>
>> #define RPC_MAX_ADDRBUFLEN (63U)
>>
>> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
>> index 759b668..fc93406 100644
>> --- a/net/sunrpc/svc.c
>> +++ b/net/sunrpc/svc.c
>> @@ -1578,3 +1578,70 @@ unsigned int svc_fill_write_vector(struct svc_rqst *rqstp, struct kvec *first,
>> return i;
>> }
>> EXPORT_SYMBOL_GPL(svc_fill_write_vector);
>> +
>> +/**
>> + * svc_fill_symlink_pathname - Construct pathname argument for VFS symlink call
>> + * @rqstp: svc_rqst to operate on
>> + * @first: buffer containing first section of pathname
>> + * @total: total length of the pathname argument
>> + *
>> + * Returns pointer to a NUL-terminated string, or an ERR_PTR. The buffer is
>> + * released automatically when @rqstp is recycled.
>> + */
>> +char *svc_fill_symlink_pathname(struct svc_rqst *rqstp, struct kvec *first,
>> + size_t total)
>> +{
>> + struct xdr_buf *arg = &rqstp->rq_arg;
>> + struct page **pages;
>> + char *result;
>> +
>> + /* VFS API demands a NUL-terminated pathname. This function
>> + * uses a page from @rqstp as the pathname buffer, to enable
>> + * direct placement. Thus the total buffer size is PAGE_SIZE.
>> + * Space in this buffer for NUL-termination requires that we
>> + * cap the size of the returned symlink pathname just a
>> + * little early.
>> + */
>> + if (total > PAGE_SIZE - 1)
>> + return ERR_PTR(-ENAMETOOLONG);
>> +
>> + /* Some types of transport can present the pathname entirely
>> + * in rq_arg.pages. If not, then copy the pathname into one
>> + * page.
>> + */
>> + pages = arg->pages;
>> + WARN_ON_ONCE(arg->page_base != 0);
>> + if (first->iov_base == 0) {
>> + result = page_address(*pages);
>> + result[total] = '\0';
>> + } else {
>> + size_t len, remaining;
>> + char *dst;
>> +
>> + result = page_address(*(rqstp->rq_next_page++));
>> + dst = result;
>> + remaining = total;
>> +
>> + len = min_t(size_t, total, first->iov_len);
>> + memcpy(dst, first->iov_base, len);
>> + dst += len;
>> + remaining -= len;
>> +
>> + /* No more than one page left */
>> + if (remaining) {
>> + len = min_t(size_t, remaining, PAGE_SIZE);
>> + memcpy(dst, page_address(*pages), len);
>> + dst += len;
>> + }
>> +
>> + *dst = '\0';
>> + }
>> +
>> + /* Sanity check: we don't allow the pathname argument to
>> + * contain a NUL byte.
>> + */
>> + if (strlen(result) != total)
>> + return ERR_PTR(-EINVAL);
>> + return result;
>> +}
>> +EXPORT_SYMBOL_GPL(svc_fill_symlink_pathname);
--
Chuck Lever
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