linux-kernel - Re: [PATCH] binder: add mutex_lock for mmap and NULL when free

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Message-ID: <a04f2f27-e746-2b28-ec58-66041def9645@quicinc.com>
Date:   Sat, 7 Oct 2023 19:43:50 +0800
From:   Kassey Li <quic_yingangl@...cinc.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <gregkh@...gle.com>, <cmllamas@...gle.com>, <surenb@...gle.com>,
        <arve@...roid.com>, <joel@...lfernandes.org>, <brauner@...nel.org>,
        <tkjos@...roid.com>, <maco@...roid.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] binder: add mutex_lock for mmap and NULL when free



On 2023/10/7 19:37, Greg KH wrote:
> On Sat, Oct 07, 2023 at 07:34:05PM +0800, Kassey Li wrote:
>>
>>
>> On 2023/10/7 19:18, Greg KH wrote:
>>> On Sat, Oct 07, 2023 at 07:07:40PM +0800, Kassey Li wrote:
>>>>
>>>>
>>>> On 2023/10/7 14:44, Greg KH wrote:
>>>>> On Sat, Oct 07, 2023 at 11:40:46AM +0800, Kassey Li wrote:
>>>>>> Enforce alloc->mutex in binder_alloc_mmap_handler when add
>>>>>> the entry to list.
>>>>>>
>>>>>> Assign the freed pages/page_ptr to NULL to catch possible
>>>>>> use after free with NULL pointer access.
>>>>>>
>>>>>> Signed-off-by: Kassey Li <quic_yingangl@...cinc.com>
>>>>>> ---
>>>>>>     drivers/android/binder_alloc.c | 5 ++++-
>>>>>>     1 file changed, 4 insertions(+), 1 deletion(-)
>>>>>
>>>>> What commit id does this fix?
>>>>
>>>>     there is no specific commit id this change going to fix.
>>>>
>>>>     it is a follow up for commit
>>>> 	19c987241ca1216a51118b2bd0185b8bc5081783  binder: separate out binder_alloc
>>>> functions (mutex lock added for list access in alloc/free)
>>>> 	f2517eb76f1f2f7f89761f9db2b202e89931738c  android: binder: Add global lru
>>>> shrinker to binder (set page->page_ptr = NULL;)
>>>>
>>>>     the background to raise this change that we are easy hit below crash in
>>>> monkey test:
>>>>
>>>> where a wrong end is passing to
>>>> binder_update_page_range, thus calculate a weird index
>>>> for
>>>>     page = &alloc->pages[index]
>>>
>>> Obviously it is a fix for some commit, please list that here.
>>
>>   ok, please kindly review this patch description according your suggest, i
>> can re-send v2 patch again.
>>
>> commit 16aaeb8556ff4eb75823c56773ee82b06bac44a0 (HEAD -> master)
>> Author: Kassey Li <quic_yingangl@...cinc.com>
>> Date:   Thu Sep 28 10:42:52 2023 +0800
>>
>>      binder: add mutex_lock for mmap and NULL when free
>>
>>      -Enforce alloc->mutex in binder_alloc_mmap_handler when add
>>      the entry to list.
>>
>>      -Assign the freed pages/page_ptr to NULL to catch possible
>>      use after free with NULL pointer access.
> 
> Odd indentation :(

thanks for the quick suggest and review, based on this version, will do 
below and send patch v2.

./scripts/checkpatch.pl 
0001-binder-add-mutex_lock-for-mmap-and-NULL-when-free.patch
total: 0 errors, 0 warnings, 26 lines checked

0001-binder-add-mutex_lock-for-mmap-and-NULL-when-free.patch has no 
obvious style problems and is ready for submission.

> 
>>      Fixes: 19c987241ca1 ("binder: separate out binder_alloc functions")
>>      Fixes: f2517eb76f1f ("android: binder: Add global lru shrinker to
>> binder")
>>      Signed-off-by: Kassey Li <quic_yingangl@...cinc.com>
> 
> Looks better than before, thanks.
> 
> greg k-h