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x86/speculation: Prevent deadlock on ssb_state::lock
commit2f5fb19341
upstream. Mikhail reported a lockdep splat related to the AMD specific ssb_state lock: CPU0 CPU1 lock(&st->lock); local_irq_disable(); lock(&(&sighand->siglock)->rlock); lock(&st->lock); <Interrupt> lock(&(&sighand->siglock)->rlock); *** DEADLOCK *** The connection between sighand->siglock and st->lock comes through seccomp, which takes st->lock while holding sighand->siglock. Make sure interrupts are disabled when __speculation_ctrl_update() is invoked via prctl() -> speculation_ctrl_update(). Add a lockdep assert to catch future offenders. Fixes:1f50ddb4f4
("x86/speculation: Handle HT correctly on AMD") Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Cc: Thomas Lendacky <thomas.lendacky@amd.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1904141948200.4917@nanos.tec.linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 6 additions and 2 deletions
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@ -411,6 +411,8 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
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u64 msr = x86_spec_ctrl_base;
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bool updmsr = false;
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lockdep_assert_irqs_disabled();
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/*
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* If TIF_SSBD is different, select the proper mitigation
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* method. Note that if SSBD mitigation is disabled or permanentely
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@ -462,10 +464,12 @@ static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)
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void speculation_ctrl_update(unsigned long tif)
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{
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unsigned long flags;
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/* Forced update. Make sure all relevant TIF flags are different */
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preempt_disable();
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local_irq_save(flags);
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__speculation_ctrl_update(~tif, tif);
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preempt_enable();
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local_irq_restore(flags);
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}
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/* Called from seccomp/prctl update */
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