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rpc: define xdr_restrict_buflen

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With this xdr_reserve_space can help us enforce various limits.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
J. Bruce Fields 2014-03-06 13:22:18 -05:00
parent 30596768b3
commit db3f58a95b
2 changed files with 30 additions and 0 deletions
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1
include/linux/sunrpc/xdr.h
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@ -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);

29
net/sunrpc/xdr.c
View File

@ -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