linux-kernel - [PATCH 3.19.y-ckt 053/170] nfsd4: fix bad bounds checking

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Message-Id: <1459558456-24452-54-git-send-email-kamal@canonical.com>
Date:	Fri,  1 Apr 2016 17:52:19 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	"J . Bruce Fields" <bfields@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 053/170] nfsd4: fix bad bounds checking

3.19.8-ckt18 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: "J. Bruce Fields" <bfields@...hat.com>

commit 4aed9c46afb80164401143aa0fdcfe3798baa9d5 upstream.

A number of spots in the xdr decoding follow a pattern like

	n = be32_to_cpup(p++);
	READ_BUF(n + 4);

where n is a u32.  The only bounds checking is done in READ_BUF itself,
but since it's checking (n + 4), it won't catch cases where n is very
large, (u32)(-4) or higher.  I'm not sure exactly what the consequences
are, but we've seen crashes soon after.

Instead, just break these up into two READ_BUF()s.

Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 fs/nfsd/nfs4xdr.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 043ed3f..841df5e 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1061,8 +1061,9 @@ nfsd4_decode_rename(struct nfsd4_compoundargs *argp, struct nfsd4_rename *rename
 
 	READ_BUF(4);
 	rename->rn_snamelen = be32_to_cpup(p++);
-	READ_BUF(rename->rn_snamelen + 4);
+	READ_BUF(rename->rn_snamelen);
 	SAVEMEM(rename->rn_sname, rename->rn_snamelen);
+	READ_BUF(4);
 	rename->rn_tnamelen = be32_to_cpup(p++);
 	READ_BUF(rename->rn_tnamelen);
 	SAVEMEM(rename->rn_tname, rename->rn_tnamelen);
@@ -1144,13 +1145,14 @@ nfsd4_decode_setclientid(struct nfsd4_compoundargs *argp, struct nfsd4_setclient
 	READ_BUF(8);
 	setclientid->se_callback_prog = be32_to_cpup(p++);
 	setclientid->se_callback_netid_len = be32_to_cpup(p++);
-
-	READ_BUF(setclientid->se_callback_netid_len + 4);
+	READ_BUF(setclientid->se_callback_netid_len);
 	SAVEMEM(setclientid->se_callback_netid_val, setclientid->se_callback_netid_len);
+	READ_BUF(4);
 	setclientid->se_callback_addr_len = be32_to_cpup(p++);
 
-	READ_BUF(setclientid->se_callback_addr_len + 4);
+	READ_BUF(setclientid->se_callback_addr_len);
 	SAVEMEM(setclientid->se_callback_addr_val, setclientid->se_callback_addr_len);
+	READ_BUF(4);
 	setclientid->se_callback_ident = be32_to_cpup(p++);
 
 	DECODE_TAIL;
@@ -1663,8 +1665,9 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)
 
 	READ_BUF(4);
 	argp->taglen = be32_to_cpup(p++);
-	READ_BUF(argp->taglen + 8);
+	READ_BUF(argp->taglen);
 	SAVEMEM(argp->tag, argp->taglen);
+	READ_BUF(8);
 	argp->minorversion = be32_to_cpup(p++);
 	argp->opcnt = be32_to_cpup(p++);
 	max_reply += 4 + (XDR_QUADLEN(argp->taglen) << 2);
-- 
2.7.4