Re: [PATCH] staging: ion: fix corruption of ion_import_dma_buf

[Shawn Lin <shawn.lin@rock-chips.com>]

在 2015/9/11 0:44, Laura Abbott 写道:
> On 09/09/2015 10:41 PM, Colin Cross wrote:
>> On Wed, Sep 9, 2015 at 10:19 AM, Laura Abbott <labbott@redhat.com> wrote:
>>> (adding Colin and John)
>>>
>>>
>>> On 09/09/2015 12:41 AM, Shawn Lin wrote:
>>>>
>>>> we found this issue but still exit in lastest kernel. Simply
>>>> keep ion_handle_create under mutex_lock to avoid this race.
>>>>
>>>> WARNING: CPU: 2 PID: 2648 at drivers/staging/android/ion/ion.c:512
>>>> ion_handle_add+0xb4/0xc0()
>>>> ion_handle_add: buffer already found.
>>>> Modules linked in: iwlmvm iwlwifi mac80211 cfg80211 compat
>>>> CPU: 2 PID: 2648 Comm: TimedEventQueue Tainted: G        W    3.14.0 #7
>>>>    00000000 00000000 9a3efd2c 80faf273 9a3efd6c 9a3efd5c 80935dc9
>>>> 811d7fd3
>>>>    9a3efd88 00000a58 812208a0 00000200 80e128d4 80e128d4 8d4ae00c
>>>> a8cd8600
>>>>    a8cd8094 9a3efd74 80935e0e 00000009 9a3efd6c 811d7fd3 9a3efd88
>>>> 9a3efd9c
>>>> Call Trace:
>>>>     [<80faf273>] dump_stack+0x48/0x69
>>>>     [<80935dc9>] warn_slowpath_common+0x79/0x90
>>>>     [<80e128d4>] ? ion_handle_add+0xb4/0xc0
>>>>     [<80e128d4>] ? ion_handle_add+0xb4/0xc0
>>>>     [<80935e0e>] warn_slowpath_fmt+0x2e/0x30
>>>>     [<80e128d4>] ion_handle_add+0xb4/0xc0
>>>>     [<80e144cc>] ion_import_dma_buf+0x8c/0x110
>>>>     [<80c517c4>] reg_init+0x364/0x7d0
>>>>     [<80993363>] ? futex_wait+0x123/0x210
>>>>     [<80992e0e>] ? get_futex_key+0x16e/0x1e0
>>>>     [<8099308f>] ? futex_wake+0x5f/0x120
>>>>     [<80c51e19>] vpu_service_ioctl+0x1e9/0x500
>>>>     [<80994aec>] ? do_futex+0xec/0x8e0
>>>>     [<80971080>] ? prepare_to_wait_event+0xc0/0xc0
>>>>     [<80c51c30>] ? reg_init+0x7d0/0x7d0
>>>>     [<80a22562>] do_vfs_ioctl+0x2d2/0x4c0
>>>>     [<80b198ad>] ? inode_has_perm.isra.41+0x2d/0x40
>>>>     [<80b199cf>] ? file_has_perm+0x7f/0x90
>>>>     [<80b1a5f7>] ? selinux_file_ioctl+0x47/0xf0
>>>>     [<80a227a8>] SyS_ioctl+0x58/0x80
>>>>     [<80fb45e8>] syscall_call+0x7/0x7
>>>>     [<80fb0000>] ? mmc_do_calc_max_discard+0xab/0xe4
>>>>
>>>> Fixes: 83271f626 ("ion: hold reference to handle...")
>>>> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
>>>> ---
>>>>
>>>>    drivers/staging/android/ion/ion.c | 6 +++---
>>>>    1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/staging/android/ion/ion.c
>>>> b/drivers/staging/android/ion/ion.c
>>>> index eec878e..32e7b5c 100644
>>>> --- a/drivers/staging/android/ion/ion.c
>>>> +++ b/drivers/staging/android/ion/ion.c
>>>> @@ -1179,13 +1179,13 @@ struct ion_handle *ion_import_dma_buf(struct
>>>> ion_client *client, int fd)
>>>>                  mutex_unlock(&client->lock);
>>>>                  goto end;
>>>>          }
>>>> -       mutex_unlock(&client->lock);
>>>>
>>>>          handle = ion_handle_create(client, buffer);
>>>> -       if (IS_ERR(handle))
>>>> +       if (IS_ERR(handle)) {
>>>> +               mutex_unlock(&client->lock);
>>>>                  goto end;
>>>> +       }
>>>>
>>>> -       mutex_lock(&client->lock);
>>>>          ret = ion_handle_add(client, handle);
>>>>          mutex_unlock(&client->lock);
>>>>          if (ret) {
>>>>
>>>
>>> So the patch looks correct but the locking change there seems like it
>>> was
>>> added
>>> deliberately. Colin/John, do you remember why the locking for
>>> ion_import_dma_buf
>>> changed? Was there a deadlock condition somewhere?
>>>
>>> Thanks,
>>> Laura
>>
>> I can't see any reason to not hold the mutex across ion_handle_create.
>> The patch that introduced the bug
>> (83271f6262c91a49df325c52bec8f00f4de294ca, ion: hold reference to
>> handle after ion_uhandle_get) required that the mutex not be held
>> around the call to ion_handle_put, but didn't affect
>> ion_handle_create.
>
> Thanks for confirming. With that,
>

Thanks for reviewing this patch, Laura. :)

> Reviewed-by: Laura Abbott <labbott@redhat.com>
>
>
>
>


-- 
Best Regards
Shawn Lin