[PATCH 4.0 116/148] svcrpc: fix potential GSSX_ACCEPT_SEC_CONTEXT decoding failures

Greg Kroah-Hartman
2015-06-03T12:23:17Z

From: Scott Mayhew <smayhew@redhat.com>

commit 9507271d960a1911a51683888837d75c171cd91f upstream.

In an environment where the KDC is running Active Directory, the
exported composite name field returned in the context could be large
enough to span a page boundary. Attaching a scratch buffer to the
decoding xdr_stream helps deal with those cases.

The case where we saw this was actually due to behavior that's been
fixed in newer gss-proxy versions, but we're fixing it here too.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/sunrpc/auth_gss/gss_rpc_xdr.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

--- a/net/sunrpc/auth_gss/gss_rpc_xdr.c
+++ b/net/sunrpc/auth_gss/gss_rpc_xdr.c
@@ -793,20 +793,26 @@ int gssx_dec_accept_sec_context(struct r
{
u32 value_follows;
int err;
+ struct page *scratch;
+
+ scratch = alloc_page(GFP_KERNEL);
+ if (!scratch)
+ return -ENOMEM;
+ xdr_set_scratch_buffer(xdr, page_address(scratch), PAGE_SIZE);

/* res->status */
err = gssx_dec_status(xdr, &res->status);
if (err)
- return err;
+ goto out_free;

/* res->context_handle */
err = gssx_dec_bool(xdr, &value_follows);
if (err)
- return err;
+ goto out_free;
if (value_follows) {
err = gssx_dec_ctx(xdr, res->context_handle);
if (err)
- return err;
+ goto out_free;
} else {
res->context_handle = NULL;
}
@@ -814,11 +820,11 @@ int gssx_dec_accept_sec_context(struct r
/* res->output_token */
err = gssx_dec_bool(xdr, &value_follows);
if (err)
- return err;
+ goto out_free;
if (value_follows) {
err = gssx_dec_buffer(xdr, res->output_token);
if (err)
- return err;
+ goto out_free;
} else {
res->output_token = NULL;
}
@@ -826,14 +832,17 @@ int gssx_dec_accept_sec_context(struct r
/* res->delegated_cred_handle */
err = gssx_dec_bool(xdr, &value_follows);
if (err)
- return err;
+ goto out_free;
if (value_follows) {
/* we do not support upcall servers sending this data. */
- return -EINVAL;
+ err = -EINVAL;
+ goto out_free;
}

/* res->options */
err = gssx_dec_option_array(xdr, &res->options);

+out_free:
+ __free_page(scratch);
return err;
}