Messages in this thread | | | Date | Thu, 3 Sep 2015 08:43:31 -0400 | Subject | Re: [BUG 4.2-rc8] Interrupt occurs while apply_alternatives() is patching the handler | From | Josh Boyer <> |
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On Thu, Sep 3, 2015 at 6:41 AM, Thomas Gleixner <tglx@linutronix.de> wrote: > On Thu, 3 Sep 2015, Borislav Petkov wrote: >> On Wed, Sep 02, 2015 at 11:11:55AM +0200, Thomas Gleixner wrote: >> > static void __init_or_module add_nops(void *insns, unsigned int len) >> > { >> > + unsigned long flags; >> > + >> > + local_irq_save(flags); >> > while (len > 0) { >> >> I guess you want to optimize the len==0 case to not disable interrupts >> needlessly: >> >> if (!len) >> return; >> >> local_irq_save(flags); >> while (len > 0) >> ... > > Nah. I rather put the local_irq_save into optimize_nops(). All other > callers of add_nops() are operating on a buffer and use text_poke > after that. Aside of that optimize_nops() is missing a sync_core(). > > Updated patch below. > > Thanks, > > tglx > > -----------------> > Subject: x86/alternatives: Make optimize_nops() interrupt safe and synced > From: Thomas Gleixner <tglx@linutronix.de> > Date: Thu, 03 Sep 2015 12:34:55 +0200 > > optimize_nops() is buggy in two aspects: > > - It's not disabling interrupts across the modification > - It's lacking a sync_core() call > > Fixes: 4fd4b6e5537c 'x86/alternatives: Use optimized NOPs for padding'
Possibly CC: stable since it fixes a commit in 4.1 and 4.2?
josh
> Reported-by: "Richard W.M. Jones" <rjones@redhat.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86/kernel/alternative.c | 5 +++++ > 1 file changed, 5 insertions(+) > > Index: tip/arch/x86/kernel/alternative.c > =================================================================== > --- tip.orig/arch/x86/kernel/alternative.c > +++ tip/arch/x86/kernel/alternative.c > @@ -338,10 +338,15 @@ done: > > static void __init_or_module optimize_nops(struct alt_instr *a, u8 *instr) > { > + unsigned long flags; > + > if (instr[0] != 0x90) > return; > > + local_irq_save(flags); > add_nops(instr + (a->instrlen - a->padlen), a->padlen); > + sync_core(); > + local_irq_restore(flags); > > DUMP_BYTES(instr, a->instrlen, "%p: [%d:%d) optimized NOPs: ", > instr, a->instrlen - a->padlen, a->padlen); > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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