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NFSD: Treat rq_reserved when initializing xdr_buf

PATCH In review Kinglong Mee 2 participants 2 messages Aug 7, 2014 – Aug 11, 2014

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Kinglong Mee

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#0 lore raw

PATCH 1/2 NFSD: Treat rq_reserved when initializing xdr_buf

After calling svc_reserve() with a small length,
nfsd does't treat it in svcxdr_init_encode().

So, when testing conflock, got message as,

[  970.127216] RPC request reserved 88 but used 116
Signed-off-by Kinglong Mee <[email protected]>
---
 fs/nfsd/nfs4proc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
fs/nfsd/nfs4proc.c +5 -2
index 5e0dc52..084e46e 100644
@@ -1245,17 +1245,20 @@ static void svcxdr_init_encode(struct svc_rqst *rqstp,
 	struct xdr_stream *xdr = &resp->xdr;
 	struct xdr_buf *buf = &rqstp->rq_res;
 	struct kvec *head = buf->head;
+	int tlen = 0;
 
 	xdr->buf = buf;
 	xdr->iov = head;
 	xdr->p   = head->iov_base + head->iov_len;
-	xdr->end = head->iov_base + PAGE_SIZE - rqstp->rq_auth_slack;
+	tlen = PAGE_SIZE - rqstp->rq_auth_slack;
+	xdr->end = head->iov_base + min(tlen, rqstp->rq_reserved);
 	/* Tail and page_len should be zero at this point: */
 	buf->len = buf->head[0].iov_len;
 	xdr->scratch.iov_len = 0;
 	xdr->page_ptr = buf->pages - 1;
-	buf->buflen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
+	tlen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
 		- rqstp->rq_auth_slack;
+	buf->buflen = min(tlen, rqstp->rq_reserved);
 }
 
 /*
Signature · 1 line
1.9.3
#1 lore raw
Quoted 6 lines · Kinglong Mee

After calling svc_reserve() with a small length,
nfsd does't treat it in svcxdr_init_encode().

So, when testing conflock, got message as,

[  970.127216] RPC request reserved 88 but used 116

rq_reserved should always be set no smaller than the maximum possible size of the reply, given everything we know about the request.

So the bug is that rq_reserved was set to small.

The risk of returning a reply larger than rq_reserved is a relatively rare deadlock, so I'd rather just stick to the log warning than convert it to a hard error.

The solution in this case is to fix the incorrect estimate.

--b.

Quoted 36 lines
Signed-off-by Kinglong Mee <[email protected]>
---
 fs/nfsd/nfs4proc.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
fs/nfsd/nfs4proc.c +5 -2
index 5e0dc52..084e46e 100644
@@ -1245,17 +1245,20 @@ static void svcxdr_init_encode(struct svc_rqst *rqstp,
 	struct xdr_stream *xdr = &resp->xdr;
 	struct xdr_buf *buf = &rqstp->rq_res;
 	struct kvec *head = buf->head;
+	int tlen = 0;
 
 	xdr->buf = buf;
 	xdr->iov = head;
 	xdr->p   = head->iov_base + head->iov_len;
-	xdr->end = head->iov_base + PAGE_SIZE - rqstp->rq_auth_slack;
+	tlen = PAGE_SIZE - rqstp->rq_auth_slack;
+	xdr->end = head->iov_base + min(tlen, rqstp->rq_reserved);
 	/* Tail and page_len should be zero at this point: */
 	buf->len = buf->head[0].iov_len;
 	xdr->scratch.iov_len = 0;
 	xdr->page_ptr = buf->pages - 1;
-	buf->buflen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
+	tlen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
 		- rqstp->rq_auth_slack;
+	buf->buflen = min(tlen, rqstp->rq_reserved);
 }
 
 /*
Signature · 1 line
1.9.3