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    SubjectRe: [PATCH 1/2] bluetooth: hci_ldisc: fix NULL-pointer dereference on tty_close
    Hi,

    On Thu, Mar 15, 2012, Marcel Holtmann wrote:
    > Hi Johan,
    >
    > > 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@vger.kernel.org>
    > > Signed-off-by: Johan Hovold <jhovold@gmail.com>
    > > ---
    > > drivers/bluetooth/hci_ldisc.c | 2 +-
    > > 1 files changed, 1 insertions(+), 1 deletions(-)
    >
    > Acked-by: Marcel Holtmann <marcel@holtmann.org>

    Both patches have been applied to my bluetooth-next tree. Thanks.

    Johan


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