linux-kernel - Re: [PATCH 5.10 0/9] x86/kprobes: Fix kprobe debug exception handling logic

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Date:   Fri, 4 Aug 2023 11:57:03 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Li Huafei <lihuafei1@...wei.com>
Cc:     stable@...r.kernel.org, mhiramat@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        sashal@...nel.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, xukuohai@...wei.com,
        natechancellor@...il.com, ndesaulniers@...gle.com,
        rostedt@...dmis.org, weiyongjun1@...wei.com, gustavoars@...nel.org,
        namit@...are.com, laijs@...ux.alibaba.com,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH 5.10 0/9] x86/kprobes: Fix kprobe debug exception
 handling logic

On Wed, Jul 05, 2023 at 02:46:44PM +0800, Li Huafei wrote:
> We found an issue with null pointer access due to kprobe debug exception
> error handling on 5.10, and I proposed a separate fix patch for 5.10,
> see [1]. But as Greg gave advice, we always choose to backport relevant
> patches from upstream to fix issues with stable kernels, so I made this
> patch set.
> 
> The main one we need to backport is patch 5, which uses int3 instead of
> debug trap for single-stepping, thus avoiding the problems we
> encountered with kprobe debug exception error handling. Patches 1-4 are
> pre-patches, and patches 6-9 are fixes for patch 5. The major
> modifications are patch 2 and patch 5. Patch 2 optimizes
> resume_execution() to avoid repeated instruction decoding, and patch 5
> uses int3 instead of debug trap, and as Masami said in the commit
> message this patch will change some behavior of kprobe, but it has
> almost no effect on the actual usage.
> 
> Please let me know if there are any problems, thanks!

Looks good, thanks for the backports, all now queued up.

greg k-h