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Date: Thu, 25 Jul 2019 10:29:53 -0400
From: Brad Spengler <spender@...ecurity.net>
To: oss-security@...ts.openwall.com
Subject: Re: CVE-2019-10207: linux kernel: bluetooth:
hci_uart: 0x0 address execution as nonprivileged user
Hi,
https://twitter.com/grsecurity/status/1154397455267586050
"The only "direct" ones in hci_ath.c (ath_wakeup_ar3k) are also done in
worker context: ath_hci_uart_work(), created from ath_open(). Looks
like just a DoS then"
Thanks,
-Brad
On Thu, Jul 25, 2019 at 02:46:19PM +0200, Andrey Konovalov wrote:
> On Thu, Jul 25, 2019 at 2:32 PM Vladis Dronov <vdronov@...hat.com> wrote:
> >
> > Hello,
> >
> > It was found (by the syzkaller initially) that a 0x0 address execution is
> > possible as nonprivileged user in the latest Linux kernel (considering
> > protection measures like SMEP, vm.mmap_min_addr, etc are disabled).
> >
> > The Linux kernel must have any of following config options enabled:
> >
> > CONFIG_BT_HCIUART_MRVL (easy to hit)
> > CONFIG_BT_HCIUART_QCA (hard to hit)
> > CONFIG_BT_HCIUART_BCM
> > CONFIG_BT_HCIUART_INTEL
> > CONFIG_BT_HCIUART_ATH3K
> >
> > The suggested fix is posted at:
> >
> > https://lore.kernel.org/linux-bluetooth/20190725120909.31235-1-vdronov@redhat.com/T/#u
> >
> > The bug and the reproducer are public, as they were found by the syzcaller
> > several months ago:
> >
> > https://syzkaller.appspot.com/bug?id=1b42faa2848963564a5b1b7f8c837ea7b55ffa50
> >
> > CVE-2019-10207 was assigned to this bug.
> >
> > $ id
> > uid=1000(vladis) gid=1000(vladis) groups=1000(vladis)
> > $ uname -r
> > 5.2.0
> > $ ./hci-proto-crash 11
> > proto = 11
> > ioctl(SET_HCI_UART_PROTO): Success
> > [ 99.894572] BUG: kernel NULL pointer dereference, address: 0000000000000000
> > [ 99.897287] #PF: supervisor instruction fetch in kernel mode
> > [ 99.897863] #PF: error_code(0x0010) - not-present page
> > [ 99.898389] PGD 0 P4D 0
> > [ 99.899036] Oops: 0010 [#1] SMP
> > [ 99.899795] CPU: 2 PID: 691 Comm: kworker/u17:0 Not tainted 5.2.0 #23
> > [ 99.900836] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
> > [ 99.902912] Workqueue: hci0 hci_power_on
> > [ 99.903673] RIP: 0010:0x0
> > [ 99.904416] Code: Bad RIP value.
> > [ 99.905137] RSP: 0018:ffff92d8822c7d98 EFLAGS: 00010246
> > [ 99.906014] RAX: ffffffff97e7a3e0 RBX: ffff8af7b5dd9e00 RCX: 00000000000010b2
> > [ 99.907075] RDX: 00000000ffffffff RSI: ffff92d8822c7d44 RDI: ffff8af7b46c0400
> > [ 99.908127] RBP: ffff8af7b46c0400 R08: 0000000000000000 R09: 000000000001cb00
> > [ 99.909232] R10: 000000000000001e R11: 000000000001b900 R12: ffff8af7b45d4000
> > [ 99.910332] R13: ffff8af7b45d4a08 R14: 0000000000000000 R15: 0ffff8af7b167ad0
> > [ 99.911452] FS: 0000000000000000(0000) GS:ffff8af7b7880000(0000) knlGS:0000000000000000
> > [ 99.912709] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 99.913682] CR2: ffffffffffffffd6 CR3: 000000007060a003 CR4: 00000000001606e0
> > [ 99.914764] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > [ 99.915830] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > [ 99.916877] Call Trace:
> > [ 99.917538] hci_uart_set_flow_control+0x149/0x1b0
> > [ 99.918441] mrvl_setup+0xe/0x70
> > [ 99.919209] hci_dev_do_open+0x1eb/0x690
> > [ 99.920013] ? sched_clock+0x5/0x10
> > [ 99.920784] hci_power_on+0x45/0x250
> > [ 99.921549] ? __wake_up_common_lock+0x87/0xc0
> > [ 99.922399] process_one_work+0x1c4/0x3a0
> > [ 99.923230] worker_thread+0x45/0x3c0
> > [ 99.924019] kthread+0xf3/0x130
> > [ 99.924735] ? trace_event_raw_event_workqueue_execute_start+0xb0/0xb0
> > [ 99.925755] ? kthread_park+0x80/0x80
> > [ 99.926546] ret_from_fork+0x1f/0x30
> > [ 99.927399] Modules linked in:
> > [ 99.928152] CR2: 0000000000000000
> > [ 99.928882] ---[ end trace 577d1af3066a9585 ]---
>
> Does this always happen in a worker thread? Does this therefore mean
> that this is not exploitable by a local user even if vm.mmap_min_addr
> and SMEP/SMAP are disabled, since the user can't mmap zero page in the
> worker thread context?
>
> >
> > Best regards,
> > Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer
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