> On Jan 25, 2018, at 8:33 AM, Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
>> On Tue, Jan 23, 2018 at 02:30:57PM -0800, Chuck Lever wrote:
>>
>>
>>> 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.
>
> Right, I think it just depends on some maximum lengths being checked
> earlier. So my worry is that this my violate some assumptions about how
> many pages we need to handle a request of a certain length.
>
> I'll go remind myself how this works. We need some documentation here
> at least.
And/or some helper functions that manage the use of rq_pages,
while updating rq_respages as needed.
> So I may end up postponing these after all....
>
>>> (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.
>
> OK, I wasn't following that case.
>
> --b.
>
>>
>> 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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