From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Mark Brown <broonie@kernel.org>
Cc: jpoimboe@redhat.com, mark.rutland@arm.com, jthierry@redhat.com,
catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org,
pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections
Date: Wed, 5 May 2021 13:48:21 -0500 [thread overview]
Message-ID: <9781011e-2d99-7f46-592c-621c66ea66c3@linux.microsoft.com> (raw)
In-Reply-To: <20210505164648.GC4541@sirena.org.uk>
On 5/5/21 11:46 AM, Mark Brown wrote:
> On Tue, May 04, 2021 at 02:32:35PM -0500, Madhavan T. Venkataraman wrote:
>
>> If you prefer, I could do something like this:
>>
>> check_pc:
>> if (!__kernel_text_address(frame->pc))
>> frame->reliable = false;
>>
>> range = lookup_range(frame->pc);
>>
>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> if (tsk->ret_stack &&
>> frame->pc == (unsigned long)return_to_handler) {
>> ...
>> frame->pc = ret_stack->ret;
>> frame->pc = ptrauth_strip_insn_pac(frame->pc);
>> goto check_pc;
>> }
>> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
>> Is that acceptable?
>
> I think that works even if it's hard to love the goto, might want some
> defensiveness to ensure we can't somehow end up in an infinite loop with
> a sufficiently badly formed stack.
>
I could do something like this:
- Move all frame->pc checking code into a function called check_frame_pc().
bool check_frame_pc(frame)
{
Do all the checks including function graph
return frame->pc changed
}
- Then, in unwind_frame()
unwind_frame()
{
int i;
...
for (i = 0; i < MAX_CHECKS; i++) {
if (!check_frame(tsk, frame))
break;
}
if (i == MAX_CHECKS)
frame->reliable = false;
return 0;
}
The above would take care of future cases like kretprobe_trampoline().
If this is acceptable, then the only question is - what should be the value of
MAX_CHECKS (I will rename it to something more appropriate)?
Madhavan
next prev parent reply other threads:[~2021-05-05 18:48 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <65cf4dfbc439b010b50a0c46ec500432acde86d6>
2021-05-03 17:36 ` [RFC PATCH v3 0/4] arm64: Stack trace reliability checks in the unwinder madvenka
2021-05-03 17:36 ` [RFC PATCH v3 1/4] arm64: Introduce stack " madvenka
2021-05-04 15:50 ` Mark Brown
2021-05-04 19:14 ` Madhavan T. Venkataraman
2021-05-04 21:52 ` Josh Poimboeuf
2021-05-04 23:13 ` Madhavan T. Venkataraman
2021-05-05 0:07 ` Josh Poimboeuf
2021-05-05 0:21 ` Madhavan T. Venkataraman
2021-05-03 17:36 ` [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections madvenka
2021-05-04 16:05 ` Mark Brown
2021-05-04 19:03 ` Madhavan T. Venkataraman
2021-05-04 19:32 ` Madhavan T. Venkataraman
2021-05-05 16:46 ` Mark Brown
2021-05-05 18:48 ` Madhavan T. Venkataraman [this message]
2021-05-05 18:50 ` Madhavan T. Venkataraman
2021-05-06 13:45 ` Mark Brown
2021-05-06 15:21 ` Madhavan T. Venkataraman
2021-05-05 16:34 ` Mark Brown
2021-05-05 17:51 ` Madhavan T. Venkataraman
2021-05-05 19:30 ` Ard Biesheuvel
2021-05-05 20:00 ` Madhavan T. Venkataraman
2021-05-03 17:36 ` [RFC PATCH v3 3/4] arm64: Handle miscellaneous functions in .text and .init.text madvenka
2021-05-06 14:12 ` Mark Brown
2021-05-06 15:30 ` Madhavan T. Venkataraman
2021-05-06 15:32 ` Madhavan T. Venkataraman
2021-05-06 15:44 ` Mark Brown
2021-05-06 15:56 ` Madhavan T. Venkataraman
2021-05-06 15:37 ` Mark Brown
2021-05-06 15:57 ` Madhavan T. Venkataraman
2021-05-03 17:36 ` [RFC PATCH v3 4/4] arm64: Handle funtion graph tracer better in the unwinder madvenka
2021-05-06 14:43 ` Mark Brown
2021-05-06 15:20 ` Madhavan T. Venkataraman
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