Fix CVE-2017-7477 (rhbz 1445207 1445208)

2 files changed, 79 insertions, 0 deletions

diff --git a/CVE-2017-7477.patch b/CVE-2017-7477.patch
new file mode 100644
index 000000000..6405614cc
--- /dev/null
+++ b/CVE-2017-7477.patch
@@ -0,0 +1,73 @@
+From 4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason@zx2c4.com>
+Date: Fri, 21 Apr 2017 23:14:48 +0200
+Subject: macsec: avoid heap overflow in skb_to_sgvec
+
+While this may appear as a humdrum one line change, it's actually quite
+important. An sk_buff stores data in three places:
+
+1. A linear chunk of allocated memory in skb->data. This is the easiest
+   one to work with, but it precludes using scatterdata since the memory
+   must be linear.
+2. The array skb_shinfo(skb)->frags, which is of maximum length
+   MAX_SKB_FRAGS. This is nice for scattergather, since these fragments
+   can point to different pages.
+3. skb_shinfo(skb)->frag_list, which is a pointer to another sk_buff,
+   which in turn can have data in either (1) or (2).
+
+The first two are rather easy to deal with, since they're of a fixed
+maximum length, while the third one is not, since there can be
+potentially limitless chains of fragments. Fortunately dealing with
+frag_list is opt-in for drivers, so drivers don't actually have to deal
+with this mess. For whatever reason, macsec decided it wanted pain, and
+so it explicitly specified NETIF_F_FRAGLIST.
+
+Because dealing with (1), (2), and (3) is insane, most users of sk_buff
+doing any sort of crypto or paging operation calls a convenient function
+called skb_to_sgvec (which happens to be recursive if (3) is in use!).
+This takes a sk_buff as input, and writes into its output pointer an
+array of scattergather list items. Sometimes people like to declare a
+fixed size scattergather list on the stack; othertimes people like to
+allocate a fixed size scattergather list on the heap. However, if you're
+doing it in a fixed-size fashion, you really shouldn't be using
+NETIF_F_FRAGLIST too (unless you're also ensuring the sk_buff and its
+frag_list children arent't shared and then you check the number of
+fragments in total required.)
+
+Macsec specifically does this:
+
+        size += sizeof(struct scatterlist) * (MAX_SKB_FRAGS + 1);
+        tmp = kmalloc(size, GFP_ATOMIC);
+        *sg = (struct scatterlist *)(tmp + sg_offset);
+	...
+        sg_init_table(sg, MAX_SKB_FRAGS + 1);
+        skb_to_sgvec(skb, sg, 0, skb->len);
+
+Specifying MAX_SKB_FRAGS + 1 is the right answer usually, but not if you're
+using NETIF_F_FRAGLIST, in which case the call to skb_to_sgvec will
+overflow the heap, and disaster ensues.
+
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+Cc: stable@vger.kernel.org
+Cc: security@kernel.org
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ drivers/net/macsec.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
+index ff0a5ed..dbab05a 100644
+--- a/drivers/net/macsec.c
++++ b/drivers/net/macsec.c
+@@ -2716,7 +2716,7 @@ static netdev_tx_t macsec_start_xmit(struct sk_buff *skb,
+ }
+ 
+ #define MACSEC_FEATURES \
+-	(NETIF_F_SG | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST)
++	(NETIF_F_SG | NETIF_F_HIGHDMA)
+ static struct lock_class_key macsec_netdev_addr_lock_key;
+ 
+ static int macsec_dev_init(struct net_device *dev)
+-- 
+cgit v1.1
+
diff --git a/kernel.spec b/kernel.spec
index 79a08987c..48004edaf 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -614,6 +614,9 @@ Patch666: powerpc-prom-Increase-RMA-size-to-512MB.patch
 # CVE-2017-7645 rhbz 1443615 1443617
 Patch667: CVE-2017-7645.patch
 
+# CVE-2017-7477 rhbz 1445207 1445208
+Patch668: CVE-2017-7477.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
@@ -2178,6 +2181,9 @@ fi
 #
 #
 %changelog
+* Tue Apr 25 2017 Justin M. Forbes <jforbes@fedoraproject.org>
+- Fix CVE-2017-7477 (rhbz 1445207 1445208)
+
 * Tue Apr 25 2017 Peter Robinson <pbrobinson@fedoraproject.org>
 - Minor ARM config cleanups