linux-kernel - Re: Catching use-after-free easily in linux kernel.

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Message-ID: <CAFf+5zgTgX6kfoaxJk_BtKOkFHGisxatayxMN4XcM_wRJw9Bnw@mail.gmail.com>
Date: Tue, 11 Mar 2025 08:59:02 +0530
From: Amit <amitchoudhary0523@...il.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: linux-kernel@...r.kernel.org
Subject: Re: Catching use-after-free easily in linux kernel.

On Tue, 11 Mar 2025 at 06:05, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Mon, Mar 10, 2025 at 01:24:54PM +0530, Amit wrote:
> > Hi,
> >
> > We can catch use-after-free easily if we do the following:
> >
> > kfree(x);
> > (x) = NULL;
> >
> > Now, if someone uses 'x' again then the kernel will crash and we will know where
> > the use-after-free is happening and then we can fix it.
>
> That assumes that no pointer is ever stored in more than one place.
> Which is very clearly false.

I will do some experiments and then I will reply if I find something.

I will introduce a global macro and then change all kfree() to this
macro name using cscope probably.

Then I will compile the kernel and run the new kernel and see if some
crash is happening or not.

My computer is x86_64, so I will be able to test only this architecture.

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