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[v3,2/6] SUNRPC: Fix svcxdr_init_encode's buflen calculation

Message ID 166205939934.1435.10147129980334935811.stgit@manet.1015granger.net (mailing list archive)
State New, archived
Headers show
Series Fixes for server-side xdr_stream overhaul | expand

Commit Message

Chuck Lever Sept. 1, 2022, 7:09 p.m. UTC
Commit 2825a7f90753 ("nfsd4: allow encoding across page boundaries")
added an explicit computation of the remaining length in the rq_res
XDR buffer.

The computation appears to suffer from an "off-by-one" bug. Because
buflen is too large by one page, XDR encoding can run off the end of
the send buffer by eventually trying to use the struct page address
in rq_page_end, which always contains NULL.

Fixes: bddfdbcddbe2 ("NFSD: Extract the svcxdr_init_encode() helper")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 include/linux/sunrpc/svc.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 5a830b66f059..0ca8a8ffb47e 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -587,7 +587,7 @@  static inline void svcxdr_init_encode(struct svc_rqst *rqstp)
 	xdr->end = resv->iov_base + PAGE_SIZE - rqstp->rq_auth_slack;
 	buf->len = resv->iov_len;
 	xdr->page_ptr = buf->pages - 1;
-	buf->buflen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages);
+	buf->buflen = PAGE_SIZE * (rqstp->rq_page_end - buf->pages);
 	buf->buflen -= rqstp->rq_auth_slack;
 	xdr->rqst = NULL;
 }