nfsd: encoders mustn't use unitialized values in error cases

In error cases, lgp->lg_layout_type may be out of bounds; so we
shouldn't be using it until after the check of nfserr.

This was seen to crash nfsd threads when the server receives a LAYOUTGET
request with a large layout type.

GETDEVICEINFO has the same problem.

Reported-by: Ari Kauppi <Ari.Kauppi@synopsys.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 33017d652b1da23165ff75ef0c8abb529ac55234..8e9652f37f1fc71af6a82c346ed7534f78732419 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4119,8 +4119,7 @@ nfsd4_encode_getdeviceinfo(struct nfsd4_compoundres *resp, __be32 nfserr,
                struct nfsd4_getdeviceinfo *gdev)
 {
        struct xdr_stream *xdr = &resp->xdr;
-       const struct nfsd4_layout_ops *ops =
-               nfsd4_layout_ops[gdev->gd_layout_type];
+       const struct nfsd4_layout_ops *ops;
        u32 starting_len = xdr->buf->len, needed_len;
        __be32 *p;
 
@@ -4137,6 +4136,7 @@ nfsd4_encode_getdeviceinfo(struct nfsd4_compoundres *resp, __be32 nfserr,
 
        /* If maxcount is 0 then just update notifications */
        if (gdev->gd_maxcount != 0) {
+               ops = nfsd4_layout_ops[gdev->gd_layout_type];
                nfserr = ops->encode_getdeviceinfo(xdr, gdev);
                if (nfserr) {
                        /*
@@ -4189,8 +4189,7 @@ nfsd4_encode_layoutget(struct nfsd4_compoundres *resp, __be32 nfserr,
                struct nfsd4_layoutget *lgp)
 {
        struct xdr_stream *xdr = &resp->xdr;
-       const struct nfsd4_layout_ops *ops =
-               nfsd4_layout_ops[lgp->lg_layout_type];
+       const struct nfsd4_layout_ops *ops;
        __be32 *p;
 
        dprintk("%s: err %d\n", __func__, nfserr);
@@ -4213,6 +4212,7 @@ nfsd4_encode_layoutget(struct nfsd4_compoundres *resp, __be32 nfserr,
        *p++ = cpu_to_be32(lgp->lg_seg.iomode);
        *p++ = cpu_to_be32(lgp->lg_layout_type);
 
+       ops = nfsd4_layout_ops[lgp->lg_layout_type];
        nfserr = ops->encode_layoutget(xdr, lgp);
 out:
        kfree(lgp->lg_content);