3.16.72-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Thomas Gleixner <[email protected]> commit 2f5fb19341883bb6e37da351bc3700489d8506a7 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: 1f50ddb4f418 ("x86/speculation: Handle HT correctly on AMD") Reported-by: Mikhail Gavrilov <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Mikhail Gavrilov <[email protected]> Cc: Thomas Lendacky <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/kernel/process.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -351,6 +351,8 @@ static __always_inline void __speculatio u64 msr = x86_spec_ctrl_base; bool updmsr = false; + lockdep_assert_irqs_disabled(); + /* * If TIF_SSBD is different, select the proper mitigation * method. Note that if SSBD mitigation is disabled or permanentely @@ -402,10 +404,12 @@ static unsigned long speculation_ctrl_up void speculation_ctrl_update(unsigned long tif) { + unsigned long flags; + /* Forced update. Make sure all relevant TIF flags are different */ - preempt_disable(); + local_irq_save(flags); __speculation_ctrl_update(~tif, tif); - preempt_enable(); + local_irq_restore(flags); } /* Called from seccomp/prctl update */
