RE: [RFC][PATCH v3 6/6] fix wrong get_user_pages usage in iovlock.c

Sosnowski, Maciej
2009-04-23T12:48:50Z

KOSAKI Motohiro wrote:
>> KOSAKI Motohiro wrote:
>>>>> I would perhaps not fold gup_fast conversions into the same patch as
>>>>> the fix.
>>>>
>>>> OK. I'll fix.
>>>
>>> Done.
>>>
>>>
>>>
>>> ===================================
>>> Subject: [Untested][RFC][PATCH] fix wrong get_user_pages usage in iovlock.c
>>>
>>> down_read(mmap_sem)
>>> get_user_pages()
>>> up_read(mmap_sem)
>>>
>>> is fork unsafe.
>>> fix it.
>>>
>>> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>>> Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
>>> Cc: David S. Miller <davem@davemloft.net>
>>> Cc: Chris Leech <christopher.leech@intel.com>
>>> Cc: netdev@vger.kernel.org
>>> ---
>>> drivers/dma/iovlock.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> Index: b/drivers/dma/iovlock.c
>>> ===================================================================
>>> --- a/drivers/dma/iovlock.c 2009-04-13 22:58:36.000000000 +0900
>>> +++ b/drivers/dma/iovlock.c 2009-04-14 20:27:16.000000000 +0900
>>> @@ -104,8 +104,6 @@ struct dma_pinned_list *dma_pin_iovec_pa 0, /* force */
>>> page_list->pages,
>>> NULL);
>>> - up_read(&current->mm->mmap_sem);
>>> -
>>> if (ret != page_list->nr_pages)
>>> goto unpin;
>>>
>>> @@ -127,6 +125,8 @@ void dma_unpin_iovec_pages(struct dma_pi if (!pinned_list)
>>> return;
>>>
>>> + up_read(&current->mm->mmap_sem);
>>> +
>>> for (i = 0; i < pinned_list->nr_iovecs; i++) {
>>> struct dma_page_list *page_list = &pinned_list->page_list[i];
>>> for (j = 0; j < page_list->nr_pages; j++) {
>>
>> I have tried it with net_dma and here is what I've got.
>
> Thanks.
> Instead, How about this?
>

Unfortuantelly still does not look good.

Regards,
Maciej

=============================================
[ INFO: possible recursive locking detected ]
2.6.30-rc2 #14
---------------------------------------------
iperf/9932 is trying to acquire lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff804e3d5e>] do_page_fault+0x170/0

but task is already holding lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff80488722>] tcp_recvmsg+0x3a/0xa7

other info that might help us debug this:
2 locks held by iperf/9932:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff80488722>] tcp_recvmsg+0x3a

#1: (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff80450965>] sk_wait_data+0

stack backtrace:
Pid: 9932, comm: iperf Tainted: G W 2.6.30-rc2 #14
Call Trace:
[<ffffffff8025b861>] ? validate_chain+0x55a/0xc7c
[<ffffffff8025c6e6>] ? __lock_acquire+0x763/0x7ec
[<ffffffff8025c835>] ? lock_acquire+0xc6/0xea
[<ffffffff804e3d5e>] ? do_page_fault+0x170/0x29d
[<ffffffff804e0693>] ? down_read+0x46/0x77
[<ffffffff804e3d5e>] ? do_page_fault+0x170/0x29d
[<ffffffff804e3d5e>] ? do_page_fault+0x170/0x29d
[<ffffffff804e1ebf>] ? page_fault+0x1f/0x30
[<ffffffff803580ed>] ? copy_user_generic_string+0x2d/0x40
[<ffffffff804562cc>] ? memcpy_toiovec+0x36/0x66
[<ffffffff804569eb>] ? skb_copy_datagram_iovec+0x133/0x1f0
[<ffffffff80490199>] ? tcp_rcv_established+0x297/0x71a
[<ffffffff804953f8>] ? tcp_v4_do_rcv+0x2c/0x1d5
[<ffffffff8024ebb3>] ? autoremove_wake_function+0x0/0x2e
[<ffffffff80486239>] ? tcp_prequeue_process+0x6b/0x7e
[<ffffffff80488b31>] ? tcp_recvmsg+0x449/0xa70
[<ffffffff8025c704>] ? __lock_acquire+0x781/0x7ec
[<ffffffff8044f5d5>] ? sock_common_recvmsg+0x30/0x45
[<ffffffff8044d81b>] ? sock_recvmsg+0xf0/0x10f
[<ffffffff80259c3c>] ? trace_hardirqs_on_caller+0x11d/0x148
[<ffffffff8024ebb3>] ? autoremove_wake_function+0x0/0x2e
[<ffffffff8020c43c>] ? restore_args+0x0/0x30
[<ffffffff802b553c>] ? fget_light+0xd5/0xdf
[<ffffffff802b54b0>] ? fget_light+0x49/0xdf
[<ffffffff8044e8ef>] ? sys_recvfrom+0xbc/0x119
[<ffffffff802331cd>] ? try_to_wake_up+0x2ae/0x2c0
[<ffffffff802718f7>] ? audit_syscall_entry+0x192/0x1bd
[<ffffffff8020b96b>] ? system_call_fastpath+0x16/0x1b