Re: [PATCH v2 3/3] NFSD: Clean up symlink argument XDR decoders

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> On Jan 23, 2018, at 12:52 PM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> 
> 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?

It's safe in the v3 case because that's what the v3
decoder currently does. I think you are concerned
about the NFSv4 COMPOUND case on TCP, for arbitrarily
large compounds? Given that we have 257-ish pages
in the rqstp->rq_pages array (ie, that number is
bounded) I'm not sure how we can ever be sure there
are enough pages for all combinations of NFS
operations.


> (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.

This case occurs when an RDMA transport has filled
in the first page of arg->pages with the symlink
contents. It's also a whole fresh page that was
obtained from rqstp->rq_pages.

Here, are you concerned about the client sending a
COMPOUND over RPC/RDMA that has more than one SYMLINK
operation? Our server currently supports only one Read
chunk per RPC.


> --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

--
Chuck Lever



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