From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: broonie@kernel.org, jpoimboe@redhat.com, jthierry@redhat.com,
catalin.marinas@arm.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack trace unreliable
Date: Tue, 23 Mar 2021 11:53:04 -0500 [thread overview]
Message-ID: <bfc4dbbd-f69b-1a41-c16a-0c5cd0080f90@linux.microsoft.com> (raw)
In-Reply-To: <20210323164801.GE98545@C02TD0UTHF1T.local>
On 3/23/21 11:48 AM, Mark Rutland wrote:
> On Tue, Mar 23, 2021 at 10:26:50AM -0500, Madhavan T. Venkataraman wrote:
>> On 3/23/21 9:57 AM, Mark Rutland wrote:
>> Thanks for explaining the nesting. It is now clear to me.
>
> No problem!
>
>> So, my next question is - can we define a practical limit for the
>> nesting so that any nesting beyond that is fatal? The reason I ask is
>> - if there is a max, then we can allocate an array of stack frames out
>> of band for the special frames so they are not part of the stack and
>> will not likely get corrupted.
>
> I suspect we can't define such a fatal limit without introducing a local
> DoS vector on some otherwise legitimate workload, and I fear this will
> further complicate the entry/exit logic, so I'd prefer to avoid
> introducing a new limit.
>
I suspected as much. But I thought I will ask anyway.
> What exactly do you mean by a "special frame", and why do those need
> additional protection over regular frame records?
>
Special frame just means pt_regs->stackframe that is used for exceptions.
No additional protection is needed. I just meant that since they are
out of band, we can reliably tell that there are exceptions without
examining the stack. That is all.
>> Also, we don't have to do any special detection. If the number of out
>> of band frames used is one or more then we have exceptions and the
>> stack trace is unreliable.
>
> What is expected to protect against?
>
It is not a protection thing. I just wanted a reliable way to tell that there
is an exception without having to unwind the stack up to the exception frame.
That is all.
Thanks.
Madhavan
WARNING: multiple messages have this Message-ID (diff)
From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: broonie@kernel.org, jpoimboe@redhat.com, jthierry@redhat.com,
catalin.marinas@arm.com, will@kernel.org,
linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack trace unreliable
Date: Tue, 23 Mar 2021 11:53:04 -0500 [thread overview]
Message-ID: <bfc4dbbd-f69b-1a41-c16a-0c5cd0080f90@linux.microsoft.com> (raw)
In-Reply-To: <20210323164801.GE98545@C02TD0UTHF1T.local>
On 3/23/21 11:48 AM, Mark Rutland wrote:
> On Tue, Mar 23, 2021 at 10:26:50AM -0500, Madhavan T. Venkataraman wrote:
>> On 3/23/21 9:57 AM, Mark Rutland wrote:
>> Thanks for explaining the nesting. It is now clear to me.
>
> No problem!
>
>> So, my next question is - can we define a practical limit for the
>> nesting so that any nesting beyond that is fatal? The reason I ask is
>> - if there is a max, then we can allocate an array of stack frames out
>> of band for the special frames so they are not part of the stack and
>> will not likely get corrupted.
>
> I suspect we can't define such a fatal limit without introducing a local
> DoS vector on some otherwise legitimate workload, and I fear this will
> further complicate the entry/exit logic, so I'd prefer to avoid
> introducing a new limit.
>
I suspected as much. But I thought I will ask anyway.
> What exactly do you mean by a "special frame", and why do those need
> additional protection over regular frame records?
>
Special frame just means pt_regs->stackframe that is used for exceptions.
No additional protection is needed. I just meant that since they are
out of band, we can reliably tell that there are exceptions without
examining the stack. That is all.
>> Also, we don't have to do any special detection. If the number of out
>> of band frames used is one or more then we have exceptions and the
>> stack trace is unreliable.
>
> What is expected to protect against?
>
It is not a protection thing. I just wanted a reliable way to tell that there
is an exception without having to unwind the stack up to the exception frame.
That is all.
Thanks.
Madhavan
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next prev parent reply other threads:[~2021-03-23 16:54 UTC|newest]
Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5997dfe8d261a3a543667b83c902883c1e4bd270>
2021-03-15 16:57 ` [RFC PATCH v2 0/8] arm64: Implement reliable stack trace madvenka
2021-03-15 16:57 ` madvenka
2021-03-15 16:57 ` [RFC PATCH v2 1/8] arm64: Implement stack trace termination record madvenka
2021-03-15 16:57 ` madvenka
2021-03-18 15:09 ` Mark Brown
2021-03-18 15:09 ` Mark Brown
2021-03-18 20:26 ` Madhavan T. Venkataraman
2021-03-18 20:26 ` Madhavan T. Venkataraman
2021-03-19 12:30 ` Mark Brown
2021-03-19 12:30 ` Mark Brown
2021-03-19 14:29 ` Madhavan T. Venkataraman
2021-03-19 14:29 ` Madhavan T. Venkataraman
2021-03-19 18:19 ` Madhavan T. Venkataraman
2021-03-19 18:19 ` Madhavan T. Venkataraman
2021-03-19 22:03 ` Madhavan T. Venkataraman
2021-03-19 22:03 ` Madhavan T. Venkataraman
2021-03-23 10:24 ` Mark Rutland
2021-03-23 10:24 ` Mark Rutland
2021-03-23 12:39 ` Madhavan T. Venkataraman
2021-03-23 12:39 ` Madhavan T. Venkataraman
2021-03-15 16:57 ` [RFC PATCH v2 2/8] arm64: Implement frame types madvenka
2021-03-15 16:57 ` madvenka
2021-03-18 17:40 ` Mark Brown
2021-03-18 17:40 ` Mark Brown
2021-03-18 22:22 ` Madhavan T. Venkataraman
2021-03-18 22:22 ` Madhavan T. Venkataraman
2021-03-19 13:22 ` Mark Brown
2021-03-19 13:22 ` Mark Brown
2021-03-19 14:40 ` Madhavan T. Venkataraman
2021-03-19 14:40 ` Madhavan T. Venkataraman
2021-03-19 15:02 ` Madhavan T. Venkataraman
2021-03-19 15:02 ` Madhavan T. Venkataraman
2021-03-19 16:20 ` Mark Brown
2021-03-19 16:20 ` Mark Brown
2021-03-19 16:27 ` Madhavan T. Venkataraman
2021-03-19 16:27 ` Madhavan T. Venkataraman
2021-03-23 10:34 ` Mark Rutland
2021-03-23 10:34 ` Mark Rutland
2021-03-15 16:57 ` [RFC PATCH v2 3/8] arm64: Terminate the stack trace at TASK_FRAME and EL0_FRAME madvenka
2021-03-15 16:57 ` madvenka
2021-03-18 18:26 ` Mark Brown
2021-03-18 18:26 ` Mark Brown
2021-03-18 20:29 ` Madhavan T. Venkataraman
2021-03-18 20:29 ` Madhavan T. Venkataraman
2021-03-23 10:36 ` Mark Rutland
2021-03-23 10:36 ` Mark Rutland
2021-03-23 12:40 ` Madhavan T. Venkataraman
2021-03-23 12:40 ` Madhavan T. Venkataraman
2021-03-15 16:57 ` [RFC PATCH v2 4/8] arm64: Detect an EL1 exception frame and mark a stack trace unreliable madvenka
2021-03-15 16:57 ` madvenka
2021-03-23 10:42 ` Mark Rutland
2021-03-23 10:42 ` Mark Rutland
2021-03-23 12:46 ` Madhavan T. Venkataraman
2021-03-23 12:46 ` Madhavan T. Venkataraman
2021-03-23 13:04 ` Mark Rutland
2021-03-23 13:04 ` Mark Rutland
2021-03-23 13:31 ` Madhavan T. Venkataraman
2021-03-23 13:31 ` Madhavan T. Venkataraman
2021-03-23 14:33 ` Mark Rutland
2021-03-23 14:33 ` Mark Rutland
2021-03-23 15:22 ` Madhavan T. Venkataraman
2021-03-23 15:22 ` Madhavan T. Venkataraman
2021-03-15 16:57 ` [RFC PATCH v2 5/8] arm64: Detect an FTRACE " madvenka
2021-03-15 16:57 ` madvenka
2021-03-23 10:51 ` Mark Rutland
2021-03-23 10:51 ` Mark Rutland
2021-03-23 12:56 ` Madhavan T. Venkataraman
2021-03-23 12:56 ` Madhavan T. Venkataraman
2021-03-23 13:36 ` Mark Rutland
2021-03-23 13:36 ` Mark Rutland
2021-03-23 13:38 ` Madhavan T. Venkataraman
2021-03-23 13:38 ` Madhavan T. Venkataraman
2021-03-23 14:15 ` Madhavan T. Venkataraman
2021-03-23 14:15 ` Madhavan T. Venkataraman
2021-03-23 14:57 ` Mark Rutland
2021-03-23 14:57 ` Mark Rutland
2021-03-23 15:26 ` Madhavan T. Venkataraman
2021-03-23 15:26 ` Madhavan T. Venkataraman
2021-03-23 16:20 ` Madhavan T. Venkataraman
2021-03-23 16:20 ` Madhavan T. Venkataraman
2021-03-23 17:02 ` Mark Rutland
2021-03-23 17:02 ` Mark Rutland
2021-03-23 17:23 ` Madhavan T. Venkataraman
2021-03-23 17:23 ` Madhavan T. Venkataraman
2021-03-23 17:27 ` Madhavan T. Venkataraman
2021-03-23 17:27 ` Madhavan T. Venkataraman
2021-03-23 18:27 ` Mark Brown
2021-03-23 18:27 ` Mark Brown
2021-03-23 20:23 ` Madhavan T. Venkataraman
2021-03-23 20:23 ` Madhavan T. Venkataraman
2021-03-23 18:30 ` Mark Rutland
2021-03-23 18:30 ` Mark Rutland
2021-03-23 20:24 ` Madhavan T. Venkataraman
2021-03-23 20:24 ` Madhavan T. Venkataraman
2021-03-23 21:04 ` Madhavan T. Venkataraman
2021-03-23 21:04 ` Madhavan T. Venkataraman
2021-03-23 16:48 ` Mark Rutland
2021-03-23 16:48 ` Mark Rutland
2021-03-23 16:53 ` Madhavan T. Venkataraman [this message]
2021-03-23 16:53 ` Madhavan T. Venkataraman
2021-03-23 17:09 ` Mark Rutland
2021-03-23 17:09 ` Mark Rutland
2021-03-15 16:57 ` [RFC PATCH v2 6/8] arm64: Check the return PC of every stack frame madvenka
2021-03-15 16:57 ` madvenka
2021-03-15 16:57 ` [RFC PATCH v2 7/8] arm64: Detect kretprobed functions in stack trace madvenka
2021-03-15 16:57 ` madvenka
2021-03-15 16:58 ` [RFC PATCH v2 8/8] arm64: Implement arch_stack_walk_reliable() madvenka
2021-03-15 16:58 ` madvenka
2021-03-15 19:01 ` [RFC PATCH v2 0/8] arm64: Implement reliable stack trace Madhavan T. Venkataraman
2021-03-15 19:01 ` Madhavan T. Venkataraman
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