[PATCH 3.19 162/177] nfsd4: fix READ permission checking

[Greg Kroah-Hartman]

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

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

From: "J. Bruce Fields" <bfields@xxxxxxxxxx>

commit 6e4891dc289cd191d46ab7ba1dcb29646644f9ca upstream.

In the case we already have a struct file (derived from a stateid), we
still need to do permission-checking; otherwise an unauthorized user
could gain access to a file by sniffing or guessing somebody else's
stateid.

Fixes: dc97618ddda9 "nfsd4: separate splice and readv cases"
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/nfsd/nfs4xdr.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3246,6 +3246,7 @@ nfsd4_encode_read(struct nfsd4_compoundr
 	unsigned long maxcount;
 	struct xdr_stream *xdr = &resp->xdr;
 	struct file *file = read->rd_filp;
+	struct svc_fh *fhp = read->rd_fhp;
 	int starting_len = xdr->buf->len;
 	struct raparms *ra;
 	__be32 *p;
@@ -3269,12 +3270,15 @@ nfsd4_encode_read(struct nfsd4_compoundr
 	maxcount = min_t(unsigned long, maxcount, (xdr->buf->buflen - xdr->buf->len));
 	maxcount = min_t(unsigned long, maxcount, read->rd_length);
 
-	if (!read->rd_filp) {
+	if (read->rd_filp)
+		err = nfsd_permission(resp->rqstp, fhp->fh_export,
+				fhp->fh_dentry,
+				NFSD_MAY_READ|NFSD_MAY_OWNER_OVERRIDE);
+	else
 		err = nfsd_get_tmp_read_open(resp->rqstp, read->rd_fhp,
 						&file, &ra);
-		if (err)
-			goto err_truncate;
-	}
+	if (err)
+		goto err_truncate;
 
 	if (file->f_op->splice_read && test_bit(RQ_SPLICE_OK, &resp->rqstp->rq_flags))
 		err = nfsd4_encode_splice_read(resp, read, file, maxcount);


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