From c1684f5035b60e9f98566493e869496fb5de1d89 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 31 Dec 2015 16:30:51 +0000 Subject: [PATCH] x86/irq: Clear move_in_progress before sending cleanup IPI send_cleanup_vector() fiddles with the old_domain mask unprotected because it relies on the protection by the move_in_progress flag. But this is fatal, as the flag is reset after the IPI has been sent. So a cpu which receives the IPI can still see the flag set and therefor ignores the cleanup request. If no other cleanup request happens then the vector stays stale on that cpu and in case of an irq removal the vector still persists. That can lead to use after free when the next cleanup IPI happens. Protect the code with vector_lock and clear move_in_progress before sending the IPI. This does not plug the race which Joe reported because: CPU0 CPU1 CPU2 lock_vector() data->move_in_progress=0 sendIPI() unlock_vector() set_affinity() assign_irq_vector() lock_vector() handle_IPI move_in_progress = 1 lock_vector() unlock_vector() move_in_progress == 1 The full fix comes with a later patch. Reported-and-tested-by: Joe Lawrence Signed-off-by: Thomas Gleixner Tested-by: Borislav Petkov Cc: Jiang Liu Cc: Jeremiah Mahler Cc: andy.shevchenko@gmail.com Cc: Guenter Roeck Cc: stable@vger.kernel.org #4.3+ Link: http://lkml.kernel.org/r/20151231160106.892412198@linutronix.de Signed-off-by: Thomas Gleixner --- arch/x86/kernel/apic/vector.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c index 68d18b338e3a..ed62f9c3f785 100644 --- a/arch/x86/kernel/apic/vector.c +++ b/arch/x86/kernel/apic/vector.c @@ -532,6 +532,8 @@ static void __send_cleanup_vector(struct apic_chip_data *data) { cpumask_var_t cleanup_mask; + raw_spin_lock(&vector_lock); + data->move_in_progress = 0; if (unlikely(!alloc_cpumask_var(&cleanup_mask, GFP_ATOMIC))) { unsigned int i; @@ -543,7 +545,7 @@ static void __send_cleanup_vector(struct apic_chip_data *data) apic->send_IPI_mask(cleanup_mask, IRQ_MOVE_CLEANUP_VECTOR); free_cpumask_var(cleanup_mask); } - data->move_in_progress = 0; + raw_spin_unlock(&vector_lock); } void send_cleanup_vector(struct irq_cfg *cfg) -- 2.20.1