From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jann Horn <jannh@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bpf: selftest for late caller stack size increase
Date: Fri, 22 Dec 2017 11:11:53 -0800 [thread overview]
Message-ID: <20171222191151.eagaah4y3eejvng7@ast-mbp> (raw)
In-Reply-To: <20171222181235.158636-1-jannh@google.com>
On Fri, Dec 22, 2017 at 07:12:35PM +0100, Jann Horn wrote:
> This checks that it is not possible to bypass the total stack size check in
> update_stack_depth() by calling a function that uses a large amount of
> stack memory *before* using a large amount of stack memory in the caller.
>
> Currently, the first added testcase causes a rejection as expected, but
> the second testcase is (AFAICS incorrectly) accepted:
>
> [...]
> #483/p calls: stack overflow using two frames (post-call access) FAIL
> Unexpected success to load!
> 0: (85) call pc+2
> caller:
> R10=fp0,call_-1
> callee:
> frame1: R1=ctx(id=0,off=0,imm=0) R10=fp0,call_0
> 3: (72) *(u8 *)(r10 -300) = 0
> 4: (b7) r0 = 0
> 5: (95) exit
> returning from callee:
> frame1: R0_w=inv0 R1=ctx(id=0,off=0,imm=0) R10=fp0,call_0
> to caller at 1:
> R0_w=inv0 R10=fp0,call_-1
>
> from 5 to 1: R0=inv0 R10=fp0,call_-1
> 1: (72) *(u8 *)(r10 -300) = 0
> 2: (95) exit
> processed 6 insns, stack depth 300+300
got it. thanks for the test!
working on a fix.
next prev parent reply other threads:[~2017-12-22 19:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-22 18:12 [PATCH] bpf: selftest for late caller stack size increase Jann Horn
2017-12-22 19:11 ` Alexei Starovoitov [this message]
2017-12-27 23:07 ` Daniel Borkmann
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