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Date: Thu, 9 Nov 2017 17:04:01 -0800 From: Kees Cook <keescook@...omium.org> To: Thomas Gleixner <tglx@...utronix.de> Cc: Arnd Bergmann <arnd@...db.de>, Anton Vorontsov <anton@...msg.org>, Colin Cross <ccross@...roid.com>, Tony Luck <tony.luck@...el.com>, John Stultz <john.stultz@...aro.org>, Stephen Boyd <sboyd@...eaurora.org>, Ingo Molnar <mingo@...nel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] pstore: use ktime_get_real_fast_ns() instead of __getnstimeofday() On Thu, Nov 9, 2017 at 4:46 PM, Thomas Gleixner <tglx@...utronix.de> wrote: > On Fri, 10 Nov 2017, Arnd Bergmann wrote: >> On Fri, Nov 10, 2017 at 12:00 AM, Thomas Gleixner <tglx@...utronix.de> wrote: >> > Hmm, no. None of the regular accessor functions can be called from NMI >> > context safely. >> >> Right, that's what I mean: it must not get called from NMI context, but it >> currently is, at least for this case: >> >> NMI handler: >> something bad >> panic() >> kmsg_dump() >> pstore_dump() >> pstore_record_init() >> __getnstimeofday() >> >> I should probably add that to the changelog text ;-) > > Indeed. Er, so, is this safe to call there? I've had to fix this a few times now, so if using ktime_get_real_fast_ns() can be used here (and doesn't return 0) then this is easily an improvement over the existing "maybe read 0" case pstore has now. -Kees -- Kees Cook Pixel Security
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