lkml.org 
[lkml]   [2018]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Date
    Subject[PATCH 3.16 227/254] pppoe: take ->needed_headroom of lower device into account on xmit
    3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Guillaume Nault <g.nault@alphalink.fr>

    commit 02612bb05e51df8489db5e94d0cf8d1c81f87b0c upstream.

    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>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/net/ppp/pppoe.c | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    --- a/drivers/net/ppp/pppoe.c
    +++ b/drivers/net/ppp/pppoe.c
    @@ -832,6 +832,7 @@ static int pppoe_sendmsg(struct kiocb *i
    struct pppoe_hdr *ph;
    struct net_device *dev;
    char *start;
    + int hlen;

    lock_sock(sk);
    if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED)) {
    @@ -850,16 +851,16 @@ static int pppoe_sendmsg(struct kiocb *i
    if (total_len > (dev->mtu + dev->hard_header_len))
    goto end;

    -
    - skb = sock_wmalloc(sk, total_len + dev->hard_header_len + 32,
    - 0, GFP_KERNEL);
    + 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_reset_network_header(skb);

    skb->dev = dev;
    @@ -920,7 +921,7 @@ static int __pppoe_xmit(struct sock *sk,
    /* 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));
    \
     
     \ /
      Last update: 2018-02-28 17:37    [W:2.595 / U:0.128 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site