linux-kernel - Re: user-controllable kmalloc size in bpf syscall

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Message-ID: <20151129182149.GA79352@ast-mbp.thefacebook.com>
Date:	Sun, 29 Nov 2015 10:21:50 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Alexei Starovoitov <ast@...nel.org>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>, daniel@...earbox.net
Subject: Re: user-controllable kmalloc size in bpf syscall

On Sun, Nov 29, 2015 at 02:18:29PM +0100, Dmitry Vyukov wrote:
>         ca.key_size = 1;
>         ca.value_size = 0xfffffff9;
>         ca.max_entries = 10;
>         int fd = syscall(SYS_bpf, BPF_MAP_CREATE, &ca, sizeof(ca));
...
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 11122 at mm/page_alloc.c:2989
> __alloc_pages_nodemask+0x695/0x14e0()

thanks for the report. That's an integer overflow :(
working on the fix.

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