[3.19.y-ckt stable] Patch "svcrpc: fix potential GSSX_ACCEPT_SEC_CONTEXT decoding failures" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    svcrpc: fix potential GSSX_ACCEPT_SEC_CONTEXT decoding failures

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 636c53da701c1e66e9f743de9fafebfc3b33ed4b Mon Sep 17 00:00:00 2001
From: Scott Mayhew <smayhew at redhat.com>
Date: Tue, 28 Apr 2015 16:29:53 -0400
Subject: svcrpc: fix potential GSSX_ACCEPT_SEC_CONTEXT decoding failures

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 at redhat.com>
Reviewed-by: Simo Sorce <simo at redhat.com>
Signed-off-by: J. Bruce Fields <bfields at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sunrpc/auth_gss/gss_rpc_xdr.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/auth_gss/gss_rpc_xdr.c b/net/sunrpc/auth_gss/gss_rpc_xdr.c
index 1ec19f6..eeeba5a 100644
--- 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 rpc_rqst *rqstp,
 {
 	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 rpc_rqst *rqstp,
 	/* 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 rpc_rqst *rqstp,
 	/* 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;
 }
--
1.9.1