From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jia-Ju Bai <baijiaju1990@gmail.com>
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 04:43:36 +0100 [thread overview]
Message-ID: <20180621034335.GT30522@ZenIV.linux.org.uk> (raw)
In-Reply-To: <ca2e4f0b-dd08-8d66-51e3-05cc69e15d65@gmail.com>
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.
next prev parent reply other threads:[~2018-06-21 3:43 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 [this message]
2018-06-21 3:50 ` Jia-Ju Bai
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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