diff --git a/debian/changelog b/debian/changelog index c444c4099..d9552c1ef 100644 --- a/debian/changelog +++ b/debian/changelog @@ -346,6 +346,7 @@ linux (4.9.24-1) UNRELEASED; urgency=medium [ Salvatore Bonaccorso ] * ping: implement proper locking (CVE-2017-2671) + * macsec: avoid heap overflow in skb_to_sgvec (CVE-2017-7477) [ Aurelien Jarno ] * [mips*/octeon] Drop obsolete patch adding support for the UBNT E200 diff --git a/debian/patches/bugfix/all/macsec-avoid-heap-overflow-in-skb_to_sgvec.patch b/debian/patches/bugfix/all/macsec-avoid-heap-overflow-in-skb_to_sgvec.patch new file mode 100644 index 000000000..63508e62c --- /dev/null +++ b/debian/patches/bugfix/all/macsec-avoid-heap-overflow-in-skb_to_sgvec.patch @@ -0,0 +1,74 @@ +From: "Jason A. Donenfeld" +Date: Fri, 21 Apr 2017 23:14:48 +0200 +Subject: macsec: avoid heap overflow in skb_to_sgvec +Origin: https://git.kernel.org/linus/4d6fa57b4dab0d77f4d8e9d9c73d1e63f6fe8fee +Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-7477 + +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 +Cc: stable@vger.kernel.org +Cc: security@kernel.org +Signed-off-by: David S. Miller +--- + 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) +-- +2.1.4 + diff --git a/debian/patches/series b/debian/patches/series index d4df7b5c2..ca0b6f56a 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -110,6 +110,7 @@ bugfix/all/net-packet-fix-overflow-in-check-for-tp_reserve.patch bugfix/all/ping-implement-proper-locking.patch bugfix/all/keys-disallow-keyrings-beginning-with-.-to-be-joined.patch bugfix/all/keys-fix-keyctl_set_reqkey_keyring-to-not-leak-threa.patch +bugfix/all/macsec-avoid-heap-overflow-in-skb_to_sgvec.patch # Fix exported symbol versions bugfix/ia64/revert-ia64-move-exports-to-definitions.patch