path: root/drivers/net/ppp
diff options
authorGuillaume Nault <g.nault@alphalink.fr>2018-01-22 18:06:37 +0100
committerDavid S. Miller <davem@davemloft.net>2018-01-23 19:44:44 -0500
commit02612bb05e51df8489db5e94d0cf8d1c81f87b0c (patch)
treea9b3d5c418c1bc74568f5108c9901fa62748f747 /drivers/net/ppp
parentMerge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net (diff)
pppoe: take ->needed_headroom of lower device into account on xmit
In pppoe_sendmsg(), reserving dev->hard_header_len bytes of headroom was probably fine before the introduction of ->needed_headroom in commit f5184d267c1a ("net: Allow netdevices to specify needed head/tailroom"). But now, virtual devices typically advertise the size of their overhead in dev->needed_headroom, so we must also take it into account in skb_reserve(). Allocation size of skb is also updated to take dev->needed_tailroom into account and replace the arbitrary 32 bytes with the real size of a PPPoE header. This issue was discovered by syzbot, who connected a pppoe socket to a gre device which had dev->header_ops->create == ipgre_header and dev->hard_header_len == 0. Therefore, PPPoE didn't reserve any headroom, and dev_hard_header() crashed when ipgre_header() tried to prepend its header to skb->data. skbuff: skb_under_panic: text:000000001d390b3a len:31 put:24 head:00000000d8ed776f data:000000008150e823 tail:0x7 end:0xc0 dev:gre0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:104! invalid opcode: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 3670 Comm: syzkaller801466 Not tainted 4.15.0-rc7-next-20180115+ #97 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:skb_panic+0x162/0x1f0 net/core/skbuff.c:100 RSP: 0018:ffff8801d9bd7840 EFLAGS: 00010282 RAX: 0000000000000083 RBX: ffff8801d4f083c0 RCX: 0000000000000000 RDX: 0000000000000083 RSI: 1ffff1003b37ae92 RDI: ffffed003b37aefc RBP: ffff8801d9bd78a8 R08: 1ffff1003b37ae8a R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff86200de0 R13: ffffffff84a981ad R14: 0000000000000018 R15: ffff8801d2d34180 FS: 00000000019c4880(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000208bc000 CR3: 00000001d9111001 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: skb_under_panic net/core/skbuff.c:114 [inline] skb_push+0xce/0xf0 net/core/skbuff.c:1714 ipgre_header+0x6d/0x4e0 net/ipv4/ip_gre.c:879 dev_hard_header include/linux/netdevice.h:2723 [inline] pppoe_sendmsg+0x58e/0x8b0 drivers/net/ppp/pppoe.c:890 sock_sendmsg_nosec net/socket.c:630 [inline] sock_sendmsg+0xca/0x110 net/socket.c:640 sock_write_iter+0x31a/0x5d0 net/socket.c:909 call_write_iter include/linux/fs.h:1775 [inline] do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:653 do_iter_write+0x154/0x540 fs/read_write.c:932 vfs_writev+0x18a/0x340 fs/read_write.c:977 do_writev+0xfc/0x2a0 fs/read_write.c:1012 SYSC_writev fs/read_write.c:1085 [inline] SyS_writev+0x27/0x30 fs/read_write.c:1082 entry_SYSCALL_64_fastpath+0x29/0xa0 Admittedly PPPoE shouldn't be allowed to run on non Ethernet-like interfaces, but reserving space for ->needed_headroom is a more fundamental issue that needs to be addressed first. Same problem exists for __pppoe_xmit(), which also needs to take dev->needed_headroom into account in skb_cow_head(). Fixes: f5184d267c1a ("net: Allow netdevices to specify needed head/tailroom") Reported-by: syzbot+ed0838d0fa4c4f2b528e20286e6dc63effc7c14d@syzkaller.appspotmail.com Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Reviewed-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ppp')
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index 4e1da1645b15..5aa59f41bf8c 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -842,6 +842,7 @@ static int pppoe_sendmsg(struct socket *sock, struct msghdr *m,
struct pppoe_hdr *ph;
struct net_device *dev;
char *start;
+ int hlen;
if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED)) {
@@ -860,16 +861,16 @@ static int pppoe_sendmsg(struct socket *sock, struct msghdr *m,
if (total_len > (dev->mtu + dev->hard_header_len))
goto end;
- skb = sock_wmalloc(sk, total_len + dev->hard_header_len + 32,
+ hlen = LL_RESERVED_SPACE(dev);
+ skb = sock_wmalloc(sk, hlen + sizeof(*ph) + total_len +
+ dev->needed_tailroom, 0, GFP_KERNEL);
if (!skb) {
error = -ENOMEM;
goto end;
/* Reserve space for headers. */
- skb_reserve(skb, dev->hard_header_len);
+ skb_reserve(skb, hlen);
skb->dev = dev;
@@ -930,7 +931,7 @@ static int __pppoe_xmit(struct sock *sk, struct sk_buff *skb)
/* Copy the data if there is no space for the header or if it's
* read-only.
- if (skb_cow_head(skb, sizeof(*ph) + dev->hard_header_len))
+ if (skb_cow_head(skb, LL_RESERVED_SPACE(dev) + sizeof(*ph)))
goto abort;
__skb_push(skb, sizeof(*ph));