From db3f58a95beea6752d90fed03f9f198d282a3913 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Thu, 6 Mar 2014 13:22:18 -0500 Subject: [PATCH] rpc: define xdr_restrict_buflen With this xdr_reserve_space can help us enforce various limits. Signed-off-by: J. Bruce Fields --- include/linux/sunrpc/xdr.h | 1 + net/sunrpc/xdr.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h index b23d69ffd5ec..70c6b92e15a7 100644 --- a/include/linux/sunrpc/xdr.h +++ b/include/linux/sunrpc/xdr.h @@ -217,6 +217,7 @@ extern void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 extern __be32 *xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes); extern void xdr_commit_encode(struct xdr_stream *xdr); extern void xdr_truncate_encode(struct xdr_stream *xdr, size_t len); +extern int xdr_restrict_buflen(struct xdr_stream *xdr, int newbuflen); extern void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int base, unsigned int len); extern unsigned int xdr_stream_pos(const struct xdr_stream *xdr); diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 2b546e8ce43d..39928444c7fb 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -648,6 +648,35 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len) } EXPORT_SYMBOL(xdr_truncate_encode); +/** + * xdr_restrict_buflen - decrease available buffer space + * @xdr: pointer to xdr_stream + * @newbuflen: new maximum number of bytes available + * + * Adjust our idea of how much space is available in the buffer. + * If we've already used too much space in the buffer, returns -1. + * If the available space is already smaller than newbuflen, returns 0 + * and does nothing. Otherwise, adjusts xdr->buf->buflen to newbuflen + * and ensures xdr->end is set at most offset newbuflen from the start + * of the buffer. + */ +int xdr_restrict_buflen(struct xdr_stream *xdr, int newbuflen) +{ + struct xdr_buf *buf = xdr->buf; + int left_in_this_buf = (void *)xdr->end - (void *)xdr->p; + int end_offset = buf->len + left_in_this_buf; + + if (newbuflen < 0 || newbuflen < buf->len) + return -1; + if (newbuflen > buf->buflen) + return 0; + if (newbuflen < end_offset) + xdr->end = (void *)xdr->end + newbuflen - end_offset; + buf->buflen = newbuflen; + return 0; +} +EXPORT_SYMBOL(xdr_restrict_buflen); + /** * xdr_write_pages - Insert a list of pages into an XDR buffer for sending * @xdr: pointer to xdr_stream -- 2.20.1