linux-kernel - Re: [PATCH v4] x86/sgx: Do not consider unsanitized pages an error

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Date:   Fri, 26 Aug 2022 04:54:26 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-sgx@...r.kernel.org
Cc:     Paul Menzel <pmenzel@...gen.mpg.de>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/sgx: Do not consider unsanitized pages an error

On Fri, Aug 26, 2022 at 04:41:26AM +0300, Jarkko Sakkinen wrote:
> In sgx_init(), if misc_register() for the provision device fails, and
> neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
> prematurely stopped.
> 
> This triggers WARN_ON() because sgx_dirty_page_list ends up being
> non-empty. Ultimately this can crash the kernel, depending on the kernel
> command line, which is not correct behavior because SGX driver is not
> working incorrectly.
> 
> Print simple warning instead, and improve the output by printing the
> number of unsanitized pages.
> 
> Link: https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u
> Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
> Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list")
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>

Speaking of non-inlining __eremove(). On a second thought, I think it
would make sense to non-inline all of __e*(). Then you can attach kprobe
to any of e-opcodes, which would be also sometimes useful for user space
debugging.

You can attach kprobe and kretprobe for each of them, and grab all
the info required.

Thoughts?

BR, Jarkko