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    Subject[21/85] Bluetooth: Fix crash in l2cap_build_cmd() with small MTU
    3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Anderson Lizardo <anderson.lizardo@openbossa.org>

    commit 300b962e5244a1ea010df7e88595faa0085b461d upstream.

    If a too small MTU value is set with ioctl(HCISETACLMTU) or by a bogus
    controller, memory corruption happens due to a memcpy() call with
    negative length.

    Fix this crash on either incoming or outgoing connections with a MTU
    smaller than L2CAP_HDR_SIZE + L2CAP_CMD_HDR_SIZE:

    [ 46.885433] BUG: unable to handle kernel paging request at f56ad000
    [ 46.888037] IP: [<c03d94cd>] memcpy+0x1d/0x40
    [ 46.888037] *pdpt = 0000000000ac3001 *pde = 00000000373f8067 *pte = 80000000356ad060
    [ 46.888037] Oops: 0002 [#1] SMP DEBUG_PAGEALLOC
    [ 46.888037] Modules linked in: hci_vhci bluetooth virtio_balloon i2c_piix4 uhci_hcd usbcore usb_common
    [ 46.888037] CPU: 0 PID: 1044 Comm: kworker/u3:0 Not tainted 3.10.0-rc1+ #12
    [ 46.888037] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
    [ 46.888037] Workqueue: hci0 hci_rx_work [bluetooth]
    [ 46.888037] task: f59b15b0 ti: f55c4000 task.ti: f55c4000
    [ 46.888037] EIP: 0060:[<c03d94cd>] EFLAGS: 00010212 CPU: 0
    [ 46.888037] EIP is at memcpy+0x1d/0x40
    [ 46.888037] EAX: f56ac1c0 EBX: fffffff8 ECX: 3ffffc6e EDX: f55c5cf2
    [ 46.888037] ESI: f55c6b32 EDI: f56ad000 EBP: f55c5c68 ESP: f55c5c5c
    [ 46.888037] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
    [ 46.888037] CR0: 8005003b CR2: f56ad000 CR3: 3557d000 CR4: 000006f0
    [ 46.888037] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
    [ 46.888037] DR6: ffff0ff0 DR7: 00000400
    [ 46.888037] Stack:
    [ 46.888037] fffffff8 00000010 00000003 f55c5cac f8c6a54c ffffffff f8c69eb2 00000000
    [ 46.888037] f4783cdc f57f0070 f759c590 1001c580 00000003 0200000a 00000000 f5a88560
    [ 46.888037] f5ba2600 f5a88560 00000041 00000000 f55c5d90 f8c6f4c7 00000008 f55c5cf2
    [ 46.888037] Call Trace:
    [ 46.888037] [<f8c6a54c>] l2cap_send_cmd+0x1cc/0x230 [bluetooth]
    [ 46.888037] [<f8c69eb2>] ? l2cap_global_chan_by_psm+0x152/0x1a0 [bluetooth]
    [ 46.888037] [<f8c6f4c7>] l2cap_connect+0x3f7/0x540 [bluetooth]
    [ 46.888037] [<c019b37b>] ? trace_hardirqs_off+0xb/0x10
    [ 46.888037] [<c01a0ff8>] ? mark_held_locks+0x68/0x110
    [ 46.888037] [<c064ad20>] ? mutex_lock_nested+0x280/0x360
    [ 46.888037] [<c064b9d9>] ? __mutex_unlock_slowpath+0xa9/0x150
    [ 46.888037] [<c01a118c>] ? trace_hardirqs_on_caller+0xec/0x1b0
    [ 46.888037] [<c064ad08>] ? mutex_lock_nested+0x268/0x360
    [ 46.888037] [<c01a125b>] ? trace_hardirqs_on+0xb/0x10
    [ 46.888037] [<f8c72f8d>] l2cap_recv_frame+0xb2d/0x1d30 [bluetooth]
    [ 46.888037] [<c01a0ff8>] ? mark_held_locks+0x68/0x110
    [ 46.888037] [<c064b9d9>] ? __mutex_unlock_slowpath+0xa9/0x150
    [ 46.888037] [<c01a118c>] ? trace_hardirqs_on_caller+0xec/0x1b0
    [ 46.888037] [<f8c754f1>] l2cap_recv_acldata+0x2a1/0x320 [bluetooth]
    [ 46.888037] [<f8c491d8>] hci_rx_work+0x518/0x810 [bluetooth]
    [ 46.888037] [<f8c48df2>] ? hci_rx_work+0x132/0x810 [bluetooth]
    [ 46.888037] [<c0158979>] process_one_work+0x1a9/0x600
    [ 46.888037] [<c01588fb>] ? process_one_work+0x12b/0x600
    [ 46.888037] [<c015922e>] ? worker_thread+0x19e/0x320
    [ 46.888037] [<c015922e>] ? worker_thread+0x19e/0x320
    [ 46.888037] [<c0159187>] worker_thread+0xf7/0x320
    [ 46.888037] [<c0159090>] ? rescuer_thread+0x290/0x290
    [ 46.888037] [<c01602f8>] kthread+0xa8/0xb0
    [ 46.888037] [<c0656777>] ret_from_kernel_thread+0x1b/0x28
    [ 46.888037] [<c0160250>] ? flush_kthread_worker+0x120/0x120
    [ 46.888037] Code: c3 90 8d 74 26 00 e8 63 fc ff ff eb e8 90 55 89 e5 83 ec 0c 89 5d f4 89 75 f8 89 7d fc 3e 8d 74 26 00 89 cb 89 c7 c1 e9 02 89 d6 <f3> a5 89 d9 83 e1 03 74 02 f3 a4 8b 5d f4 8b 75 f8 8b 7d fc 89
    [ 46.888037] EIP: [<c03d94cd>] memcpy+0x1d/0x40 SS:ESP 0068:f55c5c5c
    [ 46.888037] CR2: 00000000f56ad000
    [ 46.888037] ---[ end trace 0217c1f4d78714a9 ]---

    Signed-off-by: Anderson Lizardo <anderson.lizardo@openbossa.org>
    Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
    Signed-off-by: John W. Linville <linville@tuxdriver.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/bluetooth/l2cap_core.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/net/bluetooth/l2cap_core.c
    +++ b/net/bluetooth/l2cap_core.c
    @@ -1737,6 +1737,9 @@ static struct sk_buff *l2cap_build_cmd(s
    BT_DBG("conn %p, code 0x%2.2x, ident 0x%2.2x, len %d",
    conn, code, ident, dlen);

    + if (conn->mtu < L2CAP_HDR_SIZE + L2CAP_CMD_HDR_SIZE)
    + return NULL;
    +
    len = L2CAP_HDR_SIZE + L2CAP_CMD_HDR_SIZE + dlen;
    count = min_t(unsigned int, conn->mtu, len);



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