On Mon, Jan 22, 2018 at 05:09:35PM -0800, Chuck Lever wrote:
>
>
> > 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.
How do we know it's safe to grab another page? (Could we run out of
pages? I'd probably know the answer if I'd rewritten this code
recently, but I haven't and the details are swapped out....)
Also I don't think that's true in the first->iov_base == 0 case.
--b.
>
>
> > --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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