efi/capsule: Make efi_capsule_pending() lockless
Taking a mutex in the reboot path is bogus because we cannot sleep with interrupts disabled, such as when rebooting due to panic(), BUG: sleeping function called from invalid context at kernel/locking/mutex.c:97 in_atomic(): 0, irqs_disabled(): 1, pid: 7, name: rcu_sched Call Trace: dump_stack+0x63/0x89 ___might_sleep+0xd8/0x120 __might_sleep+0x49/0x80 mutex_lock+0x20/0x50 efi_capsule_pending+0x1d/0x60 native_machine_emergency_restart+0x59/0x280 machine_emergency_restart+0x19/0x20 emergency_restart+0x18/0x20 panic+0x1ba/0x217 In this case all other CPUs will have been stopped by the time we execute the platform reboot code, so 'capsule_pending' cannot change under our feet. We wouldn't care even if it could since we cannot wait for it complete. Also, instead of relying on the external 'system_state' variable just use a reboot notifier, so we can set 'stop_capsules' while holding 'capsule_mutex', thereby avoiding a race where system_state is updated while we're in the middle of efi_capsule_update_locked() (since CPUs won't have been stopped at that point). Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Bryan O'Donoghue <pure.logic@nexus-software.ie> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kweh Hock Leong <hock.leong.kweh@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: joeyli <jlee@suse.com> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1462570771-13324-2-git-send-email-matt@codeblueprint.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -22,11 +22,12 @@ typedef struct {
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} efi_capsule_block_desc_t;
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static bool capsule_pending;
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static bool stop_capsules;
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static int efi_reset_type = -1;
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/*
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* capsule_mutex serialises access to both capsule_pending and
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* efi_reset_type.
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* efi_reset_type and stop_capsules.
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*/
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static DEFINE_MUTEX(capsule_mutex);
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@ -50,18 +51,13 @@ static DEFINE_MUTEX(capsule_mutex);
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*/
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bool efi_capsule_pending(int *reset_type)
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{
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bool rv = false;
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mutex_lock(&capsule_mutex);
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if (!capsule_pending)
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goto out;
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return false;
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if (reset_type)
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*reset_type = efi_reset_type;
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rv = true;
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out:
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mutex_unlock(&capsule_mutex);
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return rv;
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return true;
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}
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/*
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@ -176,7 +172,7 @@ efi_capsule_update_locked(efi_capsule_header_t *capsule,
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* whether to force an EFI reboot), and we're racing against
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* that call. Abort in that case.
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*/
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if (unlikely(system_state == SYSTEM_RESTART)) {
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if (unlikely(stop_capsules)) {
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pr_warn("Capsule update raced with reboot, aborting.\n");
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return -EINVAL;
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}
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@ -298,3 +294,22 @@ out:
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return rv;
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}
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EXPORT_SYMBOL_GPL(efi_capsule_update);
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static int capsule_reboot_notify(struct notifier_block *nb, unsigned long event, void *cmd)
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{
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mutex_lock(&capsule_mutex);
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stop_capsules = true;
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mutex_unlock(&capsule_mutex);
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return NOTIFY_DONE;
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}
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static struct notifier_block capsule_reboot_nb = {
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.notifier_call = capsule_reboot_notify,
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};
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static int __init capsule_reboot_register(void)
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{
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return register_reboot_notifier(&capsule_reboot_nb);
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}
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core_initcall(capsule_reboot_register);
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