From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758871AbcEFVjj (ORCPT ); Fri, 6 May 2016 17:39:39 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:38430 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758602AbcEFVjh (ORCPT ); Fri, 6 May 2016 17:39:37 -0400 From: Matt Fleming To: Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" Cc: Matt Fleming , Ard Biesheuvel , linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, Borislav Petkov , "Bryan O'Donoghue" , joeyli , Kweh Hock Leong Subject: [PATCH 1/5] efi/capsule: Make efi_capsule_pending() lockless Date: Fri, 6 May 2016 22:39:27 +0100 Message-Id: <1462570771-13324-2-git-send-email-matt@codeblueprint.co.uk> X-Mailer: git-send-email 2.7.3 In-Reply-To: <1462570771-13324-1-git-send-email-matt@codeblueprint.co.uk> References: <1462570771-13324-1-git-send-email-matt@codeblueprint.co.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). Cc: Borislav Petkov Cc: Kweh Hock Leong Cc: Ard Biesheuvel Cc: Bryan O'Donoghue Cc: joeyli Signed-off-by: Matt Fleming --- drivers/firmware/efi/capsule.c | 36 ++++++++++++++++++++++++++---------- 1 file changed, 26 insertions(+), 10 deletions(-) diff --git a/drivers/firmware/efi/capsule.c b/drivers/firmware/efi/capsule.c index 0de55944ac0b..4703dc9b8fbd 100644 --- a/drivers/firmware/efi/capsule.c +++ b/drivers/firmware/efi/capsule.c @@ -22,11 +22,12 @@ typedef struct { } efi_capsule_block_desc_t; static bool capsule_pending; +static bool stop_capsules; static int efi_reset_type = -1; /* * capsule_mutex serialises access to both capsule_pending and - * efi_reset_type. + * efi_reset_type and stop_capsules. */ static DEFINE_MUTEX(capsule_mutex); @@ -50,18 +51,13 @@ static DEFINE_MUTEX(capsule_mutex); */ bool efi_capsule_pending(int *reset_type) { - bool rv = false; - - mutex_lock(&capsule_mutex); if (!capsule_pending) - goto out; + return false; if (reset_type) *reset_type = efi_reset_type; - rv = true; -out: - mutex_unlock(&capsule_mutex); - return rv; + + return true; } /* @@ -176,7 +172,7 @@ efi_capsule_update_locked(efi_capsule_header_t *capsule, * whether to force an EFI reboot), and we're racing against * that call. Abort in that case. */ - if (unlikely(system_state == SYSTEM_RESTART)) { + if (unlikely(stop_capsules)) { pr_warn("Capsule update raced with reboot, aborting.\n"); return -EINVAL; } @@ -298,3 +294,23 @@ out: return rv; } EXPORT_SYMBOL_GPL(efi_capsule_update); + +static int capsule_reboot_notify(struct notifier_block *nb, + unsigned long event, void *cmd) +{ + mutex_lock(&capsule_mutex); + stop_capsules = true; + mutex_unlock(&capsule_mutex); + + return NOTIFY_DONE; +} + +static struct notifier_block capsule_reboot_nb = { + .notifier_call = capsule_reboot_notify, +}; + +static int __init capsule_reboot_register(void) +{ + return register_reboot_notifier(&capsule_reboot_nb); +} +core_initcall(capsule_reboot_register); -- 2.7.3