[PATCH 2/3] bluetooth: hci_ldisc: fix NULL-pointer dereference on tty_close

From: Johan Hovold
Date: Fri Mar 09 2012 - 10:44:22 EST

Do not close protocol driver until device has been unregistered.

This fixes a race between tty_close and hci_dev_open which can result in
a NULL-pointer dereference.

The line discipline closes the protocol driver while we may still have
hci_dev_open sleeping on the req_lock mutex resulting in a NULL-pointer
dereference when lock is acquired and hci_init_req called.

Bug is 100% reproducible using hciattach and a disconnected serial port:

0. # hciattach -n ttyO1 any noflow

1. hci_dev_open called from hci_power_on grabs req lock
2. hci_init_req executes but device fails to initialise (times out
eventually)
3. hci_dev_open is called from hci_sock_ioctl and sleeps on req lock
4. hci_uart_tty_close detaches protocol driver and cancels init req
5. hci_dev_open (1) releases req lock
6. hci_dev_open (3) grabs req lock, calls hci_init_req, which triggers oops
when request is prepared in hci_uart_send_frame

[ 137.201263] Unable to handle kernel NULL pointer dereference at virtual address 00000028
[ 137.209838] pgd = c0004000
[ 137.212677] [00000028] *pgd=00000000
[ 137.216430] Internal error: Oops: 17 [#1]
[ 137.220642] Modules linked in:
[ 137.223846] CPU: 0 Tainted: G W (3.3.0-rc6-dirty #406)
[ 137.230529] PC is at __lock_acquire+0x5c/0x1ab0
[ 137.235290] LR is at lock_acquire+0x9c/0x128
[ 137.239776] pc : [<c0071490>] lr : [<c00733f8>] psr: 20000093
[ 137.239776] sp : cf869dd8 ip : c0529554 fp : c051c730
[ 137.251800] r10: 00000000 r9 : cf8673c0 r8 : 00000080
[ 137.257293] r7 : 00000028 r6 : 00000002 r5 : 00000000 r4 : c053fd70
[ 137.264129] r3 : 00000000 r2 : 00000000 r1 : 00000000 r0 : 00000001
[ 137.270965] Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel
[ 137.278717] Control: 10c5387d Table: 8f0f4019 DAC: 00000015
[ 137.284729] Process kworker/u:1 (pid: 7, stack limit = 0xcf8682e8)
[ 137.291229] Stack: (0xcf869dd8 to 0xcf86a000)
[ 137.295776] 9dc0: c0529554 00000000
[ 137.304351] 9de0: cf8673c0 cf868000 d03ea1ef cf868000 000001ef 00000470 00000000 00000002
[ 137.312927] 9e00: cf8673c0 00000001 c051c730 c00716ec 0000000c 00000440 c0529554 00000001
[ 137.321533] 9e20: c051c730 cf868000 d03ea1f3 00000000 c053b978 00000000 00000028 cf868000
[ 137.330078] 9e40: 00000000 00000000 00000002 00000000 00000000 c00733f8 00000002 00000080
[ 137.338684] 9e60: 00000000 c02a1d50 00000000 00000001 60000013 c0969a1c 60000093 c053b96c
[ 137.347259] 9e80: 00000002 00000018 20000013 c02a1d50 cf0ac000 00000000 00000002 cf868000
[ 137.355834] 9ea0: 00000089 c0374130 00000002 00000000 c02a1d50 cf0ac000 0000000c cf0fc540
[ 137.364410] 9ec0: 00000018 c02a1d50 cf0fc540 00000000 cf0fc540 c0282238 c028220c cf178d80
[ 137.372985] 9ee0: 127525d8 c02821cc 9a1fa451 c032727c 9a1fa451 127525d8 cf0fc540 cf0ac4ec
[ 137.381561] 9f00: cf0ac000 cf0fc540 cf0ac584 c03285f4 c0328580 cf0ac4ec cf85c740 c05510cc
[ 137.390136] 9f20: ce825400 c004c914 00000002 00000000 c004c884 ce8254f5 cf869f48 00000000
[ 137.398712] 9f40: c0328580 ce825415 c0a7f914 c061af64 00000000 c048cf3c cf8673c0 cf85c740
[ 137.407287] 9f60: c05510cc c051a66c c05510ec c05510c4 cf85c750 cf868000 00000089 c004d6ac
[ 137.415863] 9f80: 00000000 c0073d14 00000001 cf853ed8 cf85c740 c004d558 00000013 00000000
[ 137.424438] 9fa0: 00000000 00000000 00000000 c00516b0 00000000 00000000 cf85c740 00000000
[ 137.433013] 9fc0: 00000001 dead4ead ffffffff ffffffff c0551674 00000000 00000000 c0450aa4
[ 137.441589] 9fe0: cf869fe0 cf869fe0 cf853ed8 c005162c c0013b30 c0013b30 00ffff00 00ffff00
[ 137.450164] [<c0071490>] (__lock_acquire+0x5c/0x1ab0) from [<c00733f8>] (lock_acquire+0x9c/0x128)
[ 137.459503] [<c00733f8>] (lock_acquire+0x9c/0x128) from [<c0374130>] (_raw_spin_lock_irqsave+0x44/0x58)
[ 137.469360] [<c0374130>] (_raw_spin_lock_irqsave+0x44/0x58) from [<c02a1d50>] (skb_queue_tail+0x18/0x48)
[ 137.479339] [<c02a1d50>] (skb_queue_tail+0x18/0x48) from [<c0282238>] (h4_enqueue+0x2c/0x34)
[ 137.488189] [<c0282238>] (h4_enqueue+0x2c/0x34) from [<c02821cc>] (hci_uart_send_frame+0x34/0x68)
[ 137.497497] [<c02821cc>] (hci_uart_send_frame+0x34/0x68) from [<c032727c>] (hci_send_frame+0x50/0x88)
[ 137.507171] [<c032727c>] (hci_send_frame+0x50/0x88) from [<c03285f4>] (hci_cmd_work+0x74/0xd4)
[ 137.516204] [<c03285f4>] (hci_cmd_work+0x74/0xd4) from [<c004c914>] (process_one_work+0x1a0/0x4ec)
[ 137.525604] [<c004c914>] (process_one_work+0x1a0/0x4ec) from [<c004d6ac>] (worker_thread+0x154/0x344)
[ 137.535278] [<c004d6ac>] (worker_thread+0x154/0x344) from [<c00516b0>] (kthread+0x84/0x90)
[ 137.543975] [<c00516b0>] (kthread+0x84/0x90) from [<c0013b30>] (kernel_thread_exit+0x0/0x8)
[ 137.552734] Code: e59f4e5c e5941000 e3510000 0a000031 (e5971000)
[ 137.559234] ---[ end trace 1b75b31a2719ed1e ]---

Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
---
drivers/bluetooth/hci_ldisc.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 97c5faa..5119c4b 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -309,11 +309,11 @@ static void hci_uart_tty_close(struct tty_struct *tty)
hci_uart_close(hdev);

if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
- hu->proto->close(hu);
if (hdev) {
hci_unregister_dev(hdev);
hci_free_dev(hdev);
}
+ hu->proto->close(hu);
}
kfree(hu);
}
--
1.7.8.4

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