NFSv4: OPEN must handle the NFS4ERR_IO return code correctly

commit c7848f69ec4a8c03732cde5c949bd2aa711a9f4b upstream.

decode_op_hdr() cannot distinguish between an XDR decoding error and
the perfectly valid errorcode NFS4ERR_IO. This is normally not a
problem, but for the particular case of OPEN, we need to be able
to increment the NFSv4 open sequence id when the server returns
a valid response.

Reported-by: J Bruce Fields <bfields@fieldses.org>
Link: http://lkml.kernel.org/r/20131204210356.GA19452@fieldses.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 31 insertions, 16 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 4be8d135ed61..988efb4caac0 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -3002,7 +3002,8 @@ out_overflow:
         return -EIO;
 }
 
-static int decode_op_hdr(struct xdr_stream *xdr, enum nfs_opnum4 expected)
+static bool __decode_op_hdr(struct xdr_stream *xdr, enum nfs_opnum4 expected,
+                int *nfs_retval)
 {
         __be32 *p;
         uint32_t opnum;
@@ -3012,19 +3013,32 @@ static int decode_op_hdr(struct xdr_stream *xdr, enum nfs_opnum4 expected)
         if (unlikely(!p))
                 goto out_overflow;
         opnum = be32_to_cpup(p++);
-        if (opnum != expected) {
-                dprintk("nfs: Server returned operation"
-                        " %d but we issued a request for %d\n",
-                                opnum, expected);
-                return -EIO;
-        }
+        if (unlikely(opnum != expected))
+                goto out_bad_operation;
         nfserr = be32_to_cpup(p);
-        if (nfserr != NFS_OK)
-                return nfs4_stat_to_errno(nfserr);
-        return 0;
+        if (nfserr == NFS_OK)
+                *nfs_retval = 0;
+        else
+                *nfs_retval = nfs4_stat_to_errno(nfserr);
+        return true;
+out_bad_operation:
+        dprintk("nfs: Server returned operation"
+                " %d but we issued a request for %d\n",
+                        opnum, expected);
+        *nfs_retval = -EREMOTEIO;
+        return false;
 out_overflow:
         print_overflow_msg(__func__, xdr);
-        return -EIO;
+        *nfs_retval = -EIO;
+        return false;
+}
+
+static int decode_op_hdr(struct xdr_stream *xdr, enum nfs_opnum4 expected)
+{
+        int retval;
+
+        __decode_op_hdr(xdr, expected, &retval);
+        return retval;
 }
 
 /* Dummy routine */
@@ -4842,11 +4856,12 @@ static int decode_open(struct xdr_stream *xdr, struct nfs_openres *res)
         uint32_t savewords, bmlen, i;
         int status;
 
-        status = decode_op_hdr(xdr, OP_OPEN);
-        if (status != -EIO)
-                nfs_increment_open_seqid(status, res->seqid);
-        if (!status)
-                status = decode_stateid(xdr, &res->stateid);
+        if (!__decode_op_hdr(xdr, OP_OPEN, &status))
+                return status;
+        nfs_increment_open_seqid(status, res->seqid);
+        if (status)
+                return status;
+        status = decode_stateid(xdr, &res->stateid);
         if (unlikely(status))
                 return status;