linux-kernel - Re: [PATCH V6 3/6] kvm: fix double free for fast mmio eventfd

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Date:	Tue, 15 Sep 2015 09:13:39 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	gleb@...nel.org, pbonzini@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com,
	stable@...r.kernel.org
Subject: Re: [PATCH V6 3/6] kvm: fix double free for fast mmio eventfd

On Tue, 15 Sep 2015 14:41:56 +0800
Jason Wang <jasowang@...hat.com> wrote:

> We register wildcard mmio eventfd on two buses, once for KVM_MMIO_BUS
> and once on KVM_FAST_MMIO_BUS but with a single iodev
> instance. This will lead to an issue: kvm_io_bus_destroy() knows
> nothing about the devices on two buses pointing to a single dev. Which
> will lead to double free[1] during exit. Fix this by allocating two
> instances of iodevs then registering one on KVM_MMIO_BUS and another
> on KVM_FAST_MMIO_BUS.
> 
> CPU: 1 PID: 2894 Comm: qemu-system-x86 Not tainted 3.19.0-26-generic #28-Ubuntu
> Hardware name: LENOVO 2356BG6/2356BG6, BIOS G7ET96WW (2.56 ) 09/12/2013
> task: ffff88009ae0c4b0 ti: ffff88020e7f0000 task.ti: ffff88020e7f0000
> RIP: 0010:[<ffffffffc07e25d8>]  [<ffffffffc07e25d8>] ioeventfd_release+0x28/0x60 [kvm]
> RSP: 0018:ffff88020e7f3bc8  EFLAGS: 00010292
> RAX: dead000000200200 RBX: ffff8801ec19c900 RCX: 000000018200016d
> RDX: ffff8801ec19cf80 RSI: ffffea0008bf1d40 RDI: ffff8801ec19c900
> RBP: ffff88020e7f3bd8 R08: 000000002fc75a01 R09: 000000018200016d
> R10: ffffffffc07df6ae R11: ffff88022fc75a98 R12: ffff88021e7cc000
> R13: ffff88021e7cca48 R14: ffff88021e7cca50 R15: ffff8801ec19c880
> FS:  00007fc1ee3e6700(0000) GS:ffff88023e240000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f8f389d8000 CR3: 000000023dc13000 CR4: 00000000001427e0
> Stack:
> ffff88021e7cc000 0000000000000000 ffff88020e7f3be8 ffffffffc07e2622
> ffff88020e7f3c38 ffffffffc07df69a ffff880232524160 ffff88020e792d80
>  0000000000000000 ffff880219b78c00 0000000000000008 ffff8802321686a8
> Call Trace:
> [<ffffffffc07e2622>] ioeventfd_destructor+0x12/0x20 [kvm]
> [<ffffffffc07df69a>] kvm_put_kvm+0xca/0x210 [kvm]
> [<ffffffffc07df818>] kvm_vcpu_release+0x18/0x20 [kvm]
> [<ffffffff811f69f7>] __fput+0xe7/0x250
> [<ffffffff811f6bae>] ____fput+0xe/0x10
> [<ffffffff81093f04>] task_work_run+0xd4/0xf0
> [<ffffffff81079358>] do_exit+0x368/0xa50
> [<ffffffff81082c8f>] ? recalc_sigpending+0x1f/0x60
> [<ffffffff81079ad5>] do_group_exit+0x45/0xb0
> [<ffffffff81085c71>] get_signal+0x291/0x750
> [<ffffffff810144d8>] do_signal+0x28/0xab0
> [<ffffffff810f3a3b>] ? do_futex+0xdb/0x5d0
> [<ffffffff810b7028>] ? __wake_up_locked_key+0x18/0x20
> [<ffffffff810f3fa6>] ? SyS_futex+0x76/0x170
> [<ffffffff81014fc9>] do_notify_resume+0x69/0xb0
> [<ffffffff817cb9af>] int_signal+0x12/0x17
> Code: 5d c3 90 0f 1f 44 00 00 55 48 89 e5 53 48 89 fb 48 83 ec 08 48 8b 7f 20 e8 06 d6 a5 c0 48 8b 43 08 48 8b 13 48 89 df 48 89 42 08 <48> 89 10 48 b8 00 01 10 00 00
>  RIP  [<ffffffffc07e25d8>] ioeventfd_release+0x28/0x60 [kvm]
>  RSP <ffff88020e7f3bc8>
> 
> Cc: stable@...r.kernel.org
> Cc: Gleb Natapov <gleb@...nel.org>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
>  virt/kvm/eventfd.c | 43 +++++++++++++++++++++++++------------------
>  1 file changed, 25 insertions(+), 18 deletions(-)

Reviewed-by: Cornelia Huck <cornelia.huck@...ibm.com>

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