[RFC][PATCH v2 1/3] efivars: Disable external interrupt whileholding efivars->lock

[Seiji Aguchi]

[Problem]
 Currently, efivars doesn't disable interrupt while taking efivars->lock.
 So, there is a risk to be deadlocking in a write callback of efi_pstore
 if kernel panics in interrupt context while taking efivars->lock.

[Patch Description]
 This patch disables an external interruption while holding efivars->lock by
 replacing spin_lock/spin_unlock with spin_lock_irqsave/spin_unlock_irqrestore.

 As for spin_locks in open/close callbacks of efi_pstore which works in process
 context, they are replaced with spin_lock_irq/spin_unlock_irq. 

Signed-off-by: Seiji Aguchi <seiji.aguchi@xxxxxxx>
---
 drivers/firmware/efivars.c |   47 +++++++++++++++++++++++++------------------
 1 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 47408e8..25d6d35 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -393,10 +393,11 @@ static efi_status_t
 get_var_data(struct efivars *efivars, struct efi_variable *var)
 {
 	efi_status_t status;
+	unsigned long flags;
 
-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 	status = get_var_data_locked(efivars, var);
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);
 
 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
@@ -488,6 +489,7 @@ efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
 	struct efi_variable *new_var, *var = &entry->var;
 	struct efivars *efivars = entry->efivars;
 	efi_status_t status = EFI_NOT_FOUND;
+	unsigned long flags;
 
 	if (count != sizeof(struct efi_variable))
 		return -EINVAL;
@@ -514,14 +516,14 @@ efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
 		return -EINVAL;
 	}
 
-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 	status = efivars->ops->set_variable(new_var->VariableName,
 					    &new_var->VendorGuid,
 					    new_var->Attributes,
 					    new_var->DataSize,
 					    new_var->Data);
 
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);
 
 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
@@ -632,7 +634,7 @@ static int efi_pstore_open(struct pstore_info *psi)
 {
 	struct efivars *efivars = psi->data;
 
-	spin_lock(&efivars->lock);
+	spin_lock_irq(&efivars->lock);
 	efivars->walk_entry = list_first_entry(&efivars->list,
 					       struct efivar_entry, list);
 	return 0;
@@ -642,7 +644,7 @@ static int efi_pstore_close(struct pstore_info *psi)
 {
 	struct efivars *efivars = psi->data;
 
-	spin_unlock(&efivars->lock);
+	spin_unlock_irq(&efivars->lock);
 	return 0;
 }
 
@@ -696,11 +698,12 @@ static int efi_pstore_write(enum pstore_type_id type,
 	struct efivars *efivars = psi->data;
 	struct efivar_entry *entry, *found = NULL;
 	int i, ret = 0;
+	unsigned long flags;
 
 	sprintf(stub_name, "dump-type%u-%u-", type, part);
 	sprintf(name, "%s%lu", stub_name, get_seconds());
 
-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 
 	for (i = 0; i < DUMP_NAME_LEN; i++)
 		efi_name[i] = stub_name[i];
@@ -738,7 +741,7 @@ static int efi_pstore_write(enum pstore_type_id type,
 	efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
 				   size, psi->buf);
 
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);
 
 	if (found)
 		efivar_unregister(found);
@@ -812,6 +815,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 	unsigned long strsize1, strsize2;
 	efi_status_t status = EFI_NOT_FOUND;
 	int found = 0;
+	unsigned long flags;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
@@ -822,7 +826,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 		return -EINVAL;
 	}
 
-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 
 	/*
 	 * Does this variable already exist?
@@ -840,7 +844,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 		}
 	}
 	if (found) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irqrestore(&efivars->lock, flags);
 		return -EINVAL;
 	}
 
@@ -854,10 +858,10 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
 			status);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irqrestore(&efivars->lock, flags);
 		return -EIO;
 	}
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);
 
 	/* Create the entry in sysfs.  Locking is not required here */
 	status = efivar_create_sysfs_entry(efivars,
@@ -881,11 +885,12 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 	unsigned long strsize1, strsize2;
 	efi_status_t status = EFI_NOT_FOUND;
 	int found = 0;
+	unsigned long flags;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 
 	/*
 	 * Does this variable already exist?
@@ -903,7 +908,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 		}
 	}
 	if (!found) {
-		spin_unlock(&efivars->lock);
+		spin_unlock_irqrestore(&efivars->lock, flags);
 		return -EINVAL;
 	}
 	/* force the Attributes/DataSize to 0 to ensure deletion */
@@ -919,12 +924,12 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
 	if (status != EFI_SUCCESS) {
 		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
 			status);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irqrestore(&efivars->lock, flags);
 		return -EIO;
 	}
 	list_del(&search_efivar->list);
 	/* We need to release this lock before unregistering. */
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);
 	efivar_unregister(search_efivar);
 
 	/* It's dead Jim.... */
@@ -993,6 +998,7 @@ efivar_create_sysfs_entry(struct efivars *efivars,
 	int i, short_name_size = variable_name_size / sizeof(efi_char16_t) + 38;
 	char *short_name;
 	struct efivar_entry *new_efivar;
+	unsigned long flags;
 
 	short_name = kzalloc(short_name_size + 1, GFP_KERNEL);
 	new_efivar = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
@@ -1032,9 +1038,9 @@ efivar_create_sysfs_entry(struct efivars *efivars,
 	kfree(short_name);
 	short_name = NULL;
 
-	spin_lock(&efivars->lock);
+	spin_lock_irqsave(&efivars->lock, flags);
 	list_add(&new_efivar->list, &efivars->list);
-	spin_unlock(&efivars->lock);
+	spin_unlock_irqrestore(&efivars->lock, flags);
 
 	return 0;
 }
@@ -1101,11 +1107,12 @@ out_free:
 void unregister_efivars(struct efivars *efivars)
 {
 	struct efivar_entry *entry, *n;
+	unsigned long flags;
 
 	list_for_each_entry_safe(entry, n, &efivars->list, list) {
-		spin_lock(&efivars->lock);
+		spin_lock_irqsave(&efivars->lock, flags);
 		list_del(&entry->list);
-		spin_unlock(&efivars->lock);
+		spin_unlock_irqrestore(&efivars->lock, flags);
 		efivar_unregister(entry);
 	}
 	if (efivars->new_var)
-- 1.7.1
--
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