linux-kernel - Re: [BUG] mm: truncate: a possible sleep-in-atomic-context bug in truncate_exceptional_pvec

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Date:   Mon, 13 Aug 2018 17:30:55 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        ak@...ux.intel.com, mawilcox@...rosoft.com,
        viro@...iv.linux.org.uk, ross.zwisler@...ux.intel.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [BUG] mm: truncate: a possible sleep-in-atomic-context bug in
 truncate_exceptional_pvec_entries()



On 2018/8/13 16:56, Jan Kara wrote:
> Hi,
>
> On Mon 13-08-18 11:10:23, Jia-Ju Bai wrote:
>> The kernel may sleep with holding a spinlock.
>>
>> The function call paths (from bottom to top) in Linux-4.16 are:
>>
>> [FUNC] schedule
>> fs/dax.c, 259: schedule in get_unlocked_mapping_entry
>> fs/dax.c, 450: get_unlocked_mapping_entry in __dax_invalidate_mapping_entry
>> fs/dax.c, 471: __dax_invalidate_mapping_entry in dax_delete_mapping_entry
>> mm/truncate.c, 97: dax_delete_mapping_entry in
>> truncate_exceptional_pvec_entries
>> mm/truncate.c, 82: spin_lock_irq in truncate_exceptional_pvec_entries
>>
>> I do not find a good way to fix, so I only report.
>> This is found by my static analysis tool (DSAC).
> Thanks for report but this is a false positive. Note that the lock is
> acquired only if we are not operating on DAX mapping but we can get to
> dax_delete_mapping_entry() only if we are operating on DAX mapping.

Thanks for your reply :)
My tool does not well check the path condition here...
Sorry for this false report.


Best wishes,
Jia-Ju Bai