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Date:   Fri, 15 May 2020 20:26:56 +0000
From:   Luis Chamberlain <mcgrof@kernel.org>
To:     Rafael Aquini <aquini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
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Subject: Re: [PATCH v5] kernel: add panic_on_taint
Message-ID: <20200515202656.GZ11244@42.do-not-panic.com>
References: <20200515175502.146720-1-aquini@redhat.com>
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On Fri, May 15, 2020 at 01:55:02PM -0400, Rafael Aquini wrote:
> Analogously to the introduction of panic_on_warn, this patch introduces a kernel
> option named panic_on_taint in order to provide a simple and generic way to stop
> execution and catch a coredump when the kernel gets tainted by any given flag.
> 
> This is useful for debugging sessions as it avoids having to rebuild the kernel
> to explicitly add calls to panic() into the code sites that introduce the taint
> flags of interest. For instance, if one is interested in proceeding with a
> post-mortem analysis at the point a given code path is hitting a bad page
> (i.e. unaccount_page_cache_page(), or slab_bug()), a coredump can be collected
> by rebooting the kernel with 'panic_on_taint=0x20' amended to the command line.
> 
> Another, perhaps less frequent, use for this option would be as a mean for
> assuring a security policy case where only a subset of taints, or no single
> taint (in paranoid mode), is allowed for the running system.
> The optional switch 'nousertaint' is handy in this particular scenario,
> as it will avoid userspace induced crashes by writes to sysctl interface
> /proc/sys/kernel/tainted causing false positive hits for such policies.
> 
> Suggested-by: Qian Cai <cai@lca.pw>
> Signed-off-by: Rafael Aquini <aquini@redhat.com>

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis