Commit 6ed6decc authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
Browse files

[PATCH] knfsd: nfsd4: fix corruption of returned data when using 64k pages 



In v4 we grab an extra page just for the padding of returned data.  The
formula that the rpc server uses to allocate pages for the response doesn't
take into account this extra page.

Instead of adjusting those formulae, we adopt the same solution as v2 and v3,
and put the "tail" data in the same page as the "head" data.

Signed-off-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f0e2993e

fs/nfsd/nfs4xdr.c

+17 −25
Original line number Diff line number Diff line
@@ -2084,27 +2084,20 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_read 
	WRITE32(eof);

	WRITE32(maxcount);

	ADJUST_ARGS();

	resp->xbuf->head[0].iov_len = ((char*)resp->p) - (char*)resp->xbuf->head[0].iov_base;



	resp->xbuf->head[0].iov_len = (char*)p

					- (char*)resp->xbuf->head[0].iov_base;

	resp->xbuf->page_len = maxcount;



	/* read zero bytes -> don't set up tail */

	if(!maxcount)

		return 0;        



	/* set up page for remaining responses */

	svc_take_page(resp->rqstp);

	resp->xbuf->tail[0].iov_base = 

		page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);

	resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;

	/* Use rest of head for padding and remaining ops: */

	resp->rqstp->rq_restailpage = 0;

	resp->xbuf->tail[0].iov_base = p;

	resp->xbuf->tail[0].iov_len = 0;

	resp->p = resp->xbuf->tail[0].iov_base;

	resp->end = resp->p + PAGE_SIZE/4;



	if (maxcount&3) {

		*(resp->p)++ = 0;

		RESERVE_SPACE(4);

		WRITE32(0);

		resp->xbuf->tail[0].iov_base += maxcount&3;

		resp->xbuf->tail[0].iov_len = 4 - (maxcount&3);

		ADJUST_ARGS();

	}

	return 0;

}
@@ -2141,21 +2134,20 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_r 


	WRITE32(maxcount);

	ADJUST_ARGS();

	resp->xbuf->head[0].iov_len = ((char*)resp->p) - (char*)resp->xbuf->head[0].iov_base;

	resp->xbuf->head[0].iov_len = (char*)p

				- (char*)resp->xbuf->head[0].iov_base;

	resp->xbuf->page_len = maxcount;



	svc_take_page(resp->rqstp);

	resp->xbuf->tail[0].iov_base = 

		page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);

	resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;

	/* Use rest of head for padding and remaining ops: */

	resp->rqstp->rq_restailpage = 0;

	resp->xbuf->tail[0].iov_base = p;

	resp->xbuf->tail[0].iov_len = 0;

	resp->p = resp->xbuf->tail[0].iov_base;

	resp->end = resp->p + PAGE_SIZE/4;



	resp->xbuf->page_len = maxcount;

	if (maxcount&3) {

		*(resp->p)++ = 0;

		RESERVE_SPACE(4);

		WRITE32(0);

		resp->xbuf->tail[0].iov_base += maxcount&3;

		resp->xbuf->tail[0].iov_len = 4 - (maxcount&3);

		ADJUST_ARGS();

	}

	return 0;

}

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