From: Kees Cook <keescook@chromium.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Jessica Yu <jeyu@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] kernel: jump_label: fix NULL dereference bug in __jump_label_mod_update()
Date: Mon, 1 Oct 2018 09:18:14 -0700 [thread overview]
Message-ID: <CAGXu5jJhNLwt9U+73+X4-dmxOLkx-v5zvY3VN5TQz-ujipt-eA@mail.gmail.com> (raw)
In-Reply-To: <20181001081324.11553-1-ard.biesheuvel@linaro.org>
On Mon, Oct 1, 2018 at 1:13 AM, Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
> Commit 19483677684b ("jump_label: Annotate entries that operate on
> __init code earlier") refactored the code that manages runtime
> patching of jump labels in modules that are tied to static keys
> defined in other modules or in the core kernel.
>
> In the latter case, we may iterate over the static_key_mod linked
> list until we hit the entry for the core kernel, whose 'mod' field
> will be NULL, and attempt to dereference it to get at its 'state'
> member.
>
> So let's add a non-NULL check: this forces the 'init' argument of
> __jump_label_update() to false for static keys that are defined in
> the core kernel, which is appropriate given that __init annotated
> jump_label entries in the core kernel should no longer be active
> at this point (i.e., when loading modules).
>
> Fixes: 19483677684b ("jump_label: Annotate entries that operate on ...")
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Jessica Yu <jeyu@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
> ---
> kernel/jump_label.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index e8cf3ff3149c..14a7f9881745 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -516,7 +516,7 @@ static void __jump_label_mod_update(struct static_key *key)
> else
> stop = m->jump_entries + m->num_jump_entries;
> __jump_label_update(key, mod->entries, stop,
> - m->state == MODULE_STATE_COMING);
> + m && m->state == MODULE_STATE_COMING);
> }
> }
>
> --
> 2.17.1
>
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2018-10-01 16:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-01 8:13 [PATCH] kernel: jump_label: fix NULL dereference bug in __jump_label_mod_update() Ard Biesheuvel
2018-10-01 16:18 ` Kees Cook [this message]
2018-10-02 6:13 ` [tip:core/core] jump_label: Fix " tip-bot for Ard Biesheuvel
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