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Message-ID: <2023042702-shuffling-tweet-d9f6@gregkh>
Date: Thu, 27 Apr 2023 11:52:30 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: sangsup lee <k1rh4.lee@...il.com>
Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Amol Maheshwari <amahesh@....qualcomm.com>,
Arnd Bergmann <arnd@...db.de>, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] misc: fastrpc: Fix a Use after-free-bug by race
condition
On Thu, Apr 27, 2023 at 06:29:16PM +0900, sangsup lee wrote:
> Is there any comment for this issue?
What issue?
> (reference: https://www.spinics.net/lists/kernel/msg4731408.html)
Please use lore.kernel.org links, we have no control over any other
random email archive .
And the above link just points to this proposed patch.
>
>
> 2023년 3월 23일 (목) 오전 10:37, Sangsup Lee <k1rh4.lee@...il.com>님이 작성:
> >
> > From: Sangsup lee <k1rh4.lee@...il.com>
> >
> > This patch adds mutex_lock for fixing an Use-after-free bug.
> > fastrpc_req_munmap_impl can be called concurrently in multi-threded environments.
> > The buf which is allocated by list_for_each_safe can be used after another thread frees it.
How was this tested?
> >
> > Signed-off-by: Sangsup lee <k1rh4.lee@...il.com>
> > ---
> > V1 -> V2: moving the locking to ioctl.
> >
> > drivers/misc/fastrpc.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> > index 93ebd174d848..aa1cf0e9f4ed 100644
> > --- a/drivers/misc/fastrpc.c
> > +++ b/drivers/misc/fastrpc.c
> > @@ -1901,7 +1901,9 @@ static long fastrpc_device_ioctl(struct file *file, unsigned int cmd,
> > err = fastrpc_req_mmap(fl, argp);
> > break;
> > case FASTRPC_IOCTL_MUNMAP:
> > + mutex_lock(&fl->mutex);
> > err = fastrpc_req_munmap(fl, argp);
> > + mutex_unlock(&fl->mutex);
Are you sure you can call this function with the lock? If so, why isn't
the mmap ioctl also locked?
thanks,
greg k-h
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