Commit f49b68dd authored by Chuck Lever's avatar Chuck Lever Committed by J. Bruce Fields
Browse files

SUNRPC: xdr_stream_subsegment() must handle non-zero page_bases 



xdr_stream_subsegment() was introduced in commit c1346a12
("NFSD: Replace the internals of the READ_BUF() macro").

There are two call sites for xdr_stream_subsegment(). One is
nfsd4_decode_write(), and the other is nfsd4_decode_setxattr().
Currently neither of these call sites calls this API when
xdr_buf::page_base is a non-zero value.

However, I'm about to add a case where page_base will sometimes not
be zero when nfsd4_decode_write() invokes this API. Replace the
logic in xdr_stream_subsegment() that advances to the next data item
in the xdr_stream with something more generic in order to handle
this new use case.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 8e70bf27

net/sunrpc/xdr.c

+17 −15
Original line number Diff line number Diff line
@@ -1633,7 +1633,7 @@ EXPORT_SYMBOL_GPL(xdr_buf_subsegment); 
 * Sets up @subbuf to represent a portion of @xdr. The portion

 * starts at the current offset in @xdr, and extends for a length

 * of @nbytes. If this is successful, @xdr is advanced to the next

 * position following that portion.

 * XDR data item following that portion.

 *

 * Return values:

 *   %true: @subbuf has been initialized, and @xdr has been advanced.
@@ -1642,29 +1642,31 @@ EXPORT_SYMBOL_GPL(xdr_buf_subsegment); 
bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf,

			   unsigned int nbytes)

{

	unsigned int remaining, offset, len;

	unsigned int start = xdr_stream_pos(xdr);

	unsigned int remaining, len;



	if (xdr_buf_subsegment(xdr->buf, subbuf, xdr_stream_pos(xdr), nbytes))

	/* Extract @subbuf and bounds-check the fn arguments */

	if (xdr_buf_subsegment(xdr->buf, subbuf, start, nbytes))

		return false;



	if (subbuf->head[0].iov_len)

		if (!__xdr_inline_decode(xdr, subbuf->head[0].iov_len))

			return false;



	remaining = subbuf->page_len;

	offset = subbuf->page_base;

	while (remaining) {

		len = min_t(unsigned int, remaining, PAGE_SIZE) - offset;



	/* Advance @xdr by @nbytes */

	for (remaining = nbytes; remaining;) {

		if (xdr->p == xdr->end && !xdr_set_next_buffer(xdr))

			return false;

		if (!__xdr_inline_decode(xdr, len))

			return false;



		len = (char *)xdr->end - (char *)xdr->p;

		if (remaining <= len) {

			xdr->p = (__be32 *)((char *)xdr->p +

					(remaining + xdr_pad_size(nbytes)));

			break;

		}



		xdr->p = (__be32 *)((char *)xdr->p + len);

		xdr->end = xdr->p;

		remaining -= len;

		offset = 0;

	}



	xdr_stream_set_pos(xdr, start + nbytes);

	return true;

}

EXPORT_SYMBOL_GPL(xdr_stream_subsegment);