From: "Christian Brauner" <christian.brauner@ubuntu.com>
To: "Jann Horn" <jannh@google.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Todd Kjos" <tkjos@android.com>,
"Martijn Coenen" <maco@android.com>,
"Joel Fernandes" <joel@joelfernandes.org>,
"Christian Brauner" <christian@brauner.io>,
jannh@google.com
Cc: <devel@driverdev.osuosl.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] binder: Handle start==NULL in binder_update_page_range()
Date: Sat, 19 Oct 2019 15:55:18 +0200 [thread overview]
Message-ID: <BXTJW0B3Y8RD.1TSRR5G3JNB20@wittgenstein> (raw)
In-Reply-To: <20191018205631.248274-3-jannh@google.com>
On Fri Oct 18, 2019 at 10:56 PM Jann Horn wrote:
> The old loop wouldn't stop when reaching `start` if `start==NULL`, instead
> continuing backwards to index -1 and crashing.
>
> Luckily you need to be highly privileged to map things at NULL, so it's not
> a big problem.
>
> Fix it by adjusting the loop so that the loop variable is always in bounds.
>
> This patch is deliberately minimal to simplify backporting, but IMO this
> function could use a refactor. The jump labels in the second loop body are
> horrible (the error gotos should be jumping to free_range instead), and
> both loops would look nicer if they just iterated upwards through indices.
> And the up_read()+mmput() shouldn't be duplicated like that.
>
> Cc: stable@vger.kernel.org
> Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
> Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
next prev parent reply other threads:[~2019-10-19 13:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 20:56 [PATCH 1/3] binder: Fix race between mmap() and binder_alloc_print_pages() Jann Horn
2019-10-18 20:56 ` [PATCH 2/3] binder: Prevent repeated use of ->mmap() via NULL mapping Jann Horn
2019-10-19 14:07 ` Christian Brauner
2019-10-18 20:56 ` [PATCH 3/3] binder: Handle start==NULL in binder_update_page_range() Jann Horn
2019-10-19 13:55 ` Christian Brauner [this message]
2019-10-19 13:34 ` [PATCH 1/3] binder: Fix race between mmap() and binder_alloc_print_pages() Christian Brauner
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