Messages in this thread | | | Date | Fri, 1 Feb 2019 10:55:53 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/mce: Initialize "bank" when we find a fatal error in mce_no_way_out() |
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On Thu, Jan 31, 2019 at 04:33:41PM -0800, Tony Luck wrote: > Internal injection testing crashed with a console log that said: > > mce: [Hardware Error]: CPU 7: Machine Check Exception: f Bank 0: bd80000000100134 > > This caused a lot of head scratching because the MCACOD (bits 15:0) of that > status is a signature from an L1 data cache error. But Linux says that it found > it in "Bank 0", which on this model CPU only reports L1 instruction cache errors. > > The answer was that Linux doesn't initialize "m->bank" in the case that it finds > a fatal error in the mce_no_way_out() pre-scan of banks. If this was a local machine > check, then we pass this partially initialized "struct mce" to mce_panic(). > > Fix is simple. Just initialize m->bank in the case that we found a fatal error. > > Fixes: 40c36e2741d7 ("x86/mce: Fix incorrect "Machine check from unknown source" message") > Cc: stable@vger.kernel.org # v4.18 Note pre-v5.0 arch/x86/kernel/cpu/mce/core.c was called arch/x86/kernel/cpu/mcheck/mce.c > Signed-off-by: Tony Luck <tony.luck@intel.com> > --- > arch/x86/kernel/cpu/mce/core.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c > index 672c7225cb1b..6ce290c506d9 100644 > --- a/arch/x86/kernel/cpu/mce/core.c > +++ b/arch/x86/kernel/cpu/mce/core.c > @@ -784,6 +784,7 @@ static int mce_no_way_out(struct mce *m, char **msg, unsigned long *validp, > quirk_no_way_out(i, m, regs); > > if (mce_severity(m, mca_cfg.tolerant, &tmp, true) >= MCE_PANIC_SEVERITY) { > + m->bank = i;
So conceptually this write belongs in...
> mce_read_aux(m, i);
... this function, i.e., in mce_read_aux() because it gets the bank number passed in already. And our calling pattern when populating struct mce is:
mce_gather_info() mce_read_aux()
so it'll be more robust if we moved it there.
Also, that argument "i" of mce_read_aux() is not very telling and it should be "bank" but that would complicate the stable backporting so if you feel like it, you could do a second, cleanup patch ontop to fix that too.
Thx.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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