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SubjectRe: [PATCH] staging: ion: fix corruption of ion_import_dma_buf
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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,

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



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