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> Cc: stable@vger.kernel.org Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk> Signed-off-by: John W. Linville <linville@tuxdriver.com>
@@ -2852,6 +2852,9 @@ static struct sk_buff *l2cap_build_cmd(struct l2cap_conn *conn, u8 code,
BT_DBG("conn %p, code 0x%2.2x, ident 0x%2.2x, len %u",
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);
Anderson Lizardo