From: Jia-Ju Bai <baijiaju1990@gmail.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: akpm@linux-foundation.org, dvyukov@google.com,
Greg KH <gregkh@linuxfoundation.org>,
tchibo@google.com, aryabinin@virtuozzo.com,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] kernel: kcov: a possible sleep-in-atomic-context bug in kcov_ioctl()
Date: Thu, 21 Jun 2018 11:50:54 +0800 [thread overview]
Message-ID: <3dc2431d-e474-a3b6-c6c9-9f7079a9cb9b@gmail.com> (raw)
In-Reply-To: <20180621034335.GT30522@ZenIV.linux.org.uk>
On 2018/6/21 11:43, Al Viro wrote:
> On Thu, Jun 21, 2018 at 11:20:59AM +0800, Jia-Ju Bai wrote:
>> The kernel may sleep with holding a spinlock.
>> The function call path (from bottom to top) in Linux-4.16.7 is:
>>
>> [FUNC] vfree --> can sleep
>> kernel/kcov.c, 237: vfree in kcov_put
>> kernel/kcov.c, 396: kcov_put in kcov_ioctl_locked
>> kernel/kcov.c, 410: kcov_ioctl_locked in kcov_ioctl
>> kernel/kcov.c, 409: spin_lock in kcov_ioctl
>>
>> This bug is found by my static analysis tool (DSAC-2) and checked by my
>> code review.
>>
>> I do not know how to correctly fix this bug, so I just report them.
> Assuming it's a bug in the first place, that is. Note that
> * we never modify task->kcov for task != current
> * task->kcov contributes to refcount
> * opened file contributes to refcount
> * that kcov_put() of yours happens from ->ioctl() and removes
> current->kcov reference; it *can't* be the last reference - the one
> held by struct file used to call ->ioctl() is also there.
>
> IOW, it's a false positive.
Okay, thanks for your reply and explanation.
I agree that my report is false.
Best wishes,
Jia-Ju Bai
next prev parent reply other threads:[~2018-06-21 3:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-21 3:20 Jia-Ju Bai
2018-06-21 3:43 ` Al Viro
2018-06-21 3:50 ` Jia-Ju Bai [this message]
2019-12-17 12:56 Jia-Ju Bai
2019-12-17 13:02 ` Dmitry Vyukov
2019-12-17 13:11 ` Jia-Ju Bai
2019-12-17 13:13 ` Dmitry Vyukov
2019-12-17 13:17 ` Jia-Ju Bai
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