linux-kernel - [ 139/173] nfsd4: fix oops on unusual readlike compound

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Message-Id: <20121228190358.332989074@decadent.org.uk>
Date:	Fri, 28 Dec 2012 20:05:49 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	"J. Bruce Fields" <bfields@...hat.com>
Subject: [ 139/173] nfsd4: fix oops on unusual readlike compound

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "J. Bruce Fields" <bfields@...hat.com>

commit d5f50b0c290431c65377c4afa1c764e2c3fe5305 upstream.

If the argument and reply together exceed the maximum payload size, then
a reply with a read-like operation can overlow the rq_pages array.

Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nfsd/nfs4xdr.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2909,11 +2909,16 @@ nfsd4_encode_read(struct nfsd4_compoundr
 	len = maxcount;
 	v = 0;
 	while (len > 0) {
-		pn = resp->rqstp->rq_resused++;
+		pn = resp->rqstp->rq_resused;
+		if (!resp->rqstp->rq_respages[pn]) { /* ran out of pages */
+			maxcount -= len;
+			break;
+		}
 		resp->rqstp->rq_vec[v].iov_base =
 			page_address(resp->rqstp->rq_respages[pn]);
 		resp->rqstp->rq_vec[v].iov_len =
 			len < PAGE_SIZE ? len : PAGE_SIZE;
+		resp->rqstp->rq_resused++;
 		v++;
 		len -= PAGE_SIZE;
 	}
@@ -2959,6 +2964,8 @@ nfsd4_encode_readlink(struct nfsd4_compo
 		return nfserr;
 	if (resp->xbuf->page_len)
 		return nfserr_resource;
+	if (!resp->rqstp->rq_respages[resp->rqstp->rq_resused])
+		return nfserr_resource;
 
 	page = page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused++]);
 
@@ -3008,6 +3015,8 @@ nfsd4_encode_readdir(struct nfsd4_compou
 		return nfserr;
 	if (resp->xbuf->page_len)
 		return nfserr_resource;
+	if (!resp->rqstp->rq_respages[resp->rqstp->rq_resused])
+		return nfserr_resource;
 
 	RESERVE_SPACE(8);  /* verifier */
 	savep = p;


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