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Commit 81fa4e58 authored by Seiji Aguchi's avatar Seiji Aguchi Committed by Tony Luck
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efivars: Disable external interrupt while holding efivars->lock 



[Problem]
There is a scenario which efi_pstore fails to log messages in a panic case.

 - CPUA holds an efi_var->lock in either efivarfs parts
   or efi_pstore with interrupt enabled.
 - CPUB panics and sends IPI to CPUA in smp_send_stop().
 - CPUA stops with holding the lock.
 - CPUB kicks efi_pstore_write() via kmsg_dump(KSMG_DUMP_PANIC)
   but it returns without logging messages.

[Patch Description]
This patch disables an external interruption while holding efivars->lock
as follows.

In efi_pstore_write() and get_var_data(), spin_lock/spin_unlock is
replaced by spin_lock_irqsave/spin_unlock_irqrestore because they may
be called in an interrupt context.

In other functions, they are replaced by spin_lock_irq/spin_unlock_irq.
because they are all called from a process context.

By applying this patch, we can avoid the problem above with
a following senario.

 - CPUA holds an efi_var->lock with interrupt disabled.
 - CPUB panics and sends IPI to CPUA in smp_send_stop().
 - CPUA receives the IPI after releasing the lock because it is
   disabling interrupt while holding the lock.
 - CPUB waits for one sec until CPUA releases the lock.
 - CPUB kicks efi_pstore_write() via kmsg_dump(KSMG_DUMP_PANIC)
   And it can hold the lock successfully.

Signed-off-by: default avatarSeiji Aguchi <seiji.aguchi@hds.com>
Acked-by: default avatarMike Waychison <mikew@google.com>
Acked-by: default avatarMatt Fleming <matt.fleming@intel.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent e59310ad

drivers/firmware/efivars.c

+44 −42
Original line number Diff line number Diff line
@@ -405,10 +405,11 @@ 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",
@@ -537,14 +538,14 @@ efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count) 
		return -EINVAL;

	}



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);

	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_irq(&efivars->lock);



	if (status != EFI_SUCCESS) {

		printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
@@ -713,7 +714,7 @@ static ssize_t efivarfs_file_write(struct file *file, 
	 * amounts of memory. Pick a default size of 64K if

	 * QueryVariableInfo() isn't supported by the firmware.

	 */

	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);



	if (!efivars->ops->query_variable_info)

		status = EFI_UNSUPPORTED;
@@ -723,7 +724,7 @@ static ssize_t efivarfs_file_write(struct file *file, 
						   &remaining_size, &max_size);

	}



	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);



	if (status != EFI_SUCCESS) {

		if (status != EFI_UNSUPPORTED)
@@ -754,7 +755,7 @@ static ssize_t efivarfs_file_write(struct file *file, 
	 * set_variable call, and removal of the variable from the efivars

	 * list (in the case of an authenticated delete).

	 */

	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);



	status = efivars->ops->set_variable(var->var.VariableName,

					    &var->var.VendorGuid,
@@ -762,7 +763,7 @@ static ssize_t efivarfs_file_write(struct file *file, 
					    data);



	if (status != EFI_SUCCESS) {

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		kfree(data);



		return efi_status_to_err(status);
@@ -783,20 +784,20 @@ static ssize_t efivarfs_file_write(struct file *file, 
					    NULL);



	if (status == EFI_BUFFER_TOO_SMALL) {

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		mutex_lock(&inode->i_mutex);

		i_size_write(inode, newdatasize + sizeof(attributes));

		mutex_unlock(&inode->i_mutex);



	} else if (status == EFI_NOT_FOUND) {

		list_del(&var->list);

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		efivar_unregister(var);

		drop_nlink(inode);

		dput(file->f_dentry);



	} else {

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		pr_warn("efivarfs: inconsistent EFI variable implementation? "

				"status = %lx\n", status);

	}
@@ -818,11 +819,11 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf, 
	void *data;

	ssize_t size = 0;



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);

	status = efivars->ops->get_variable(var->var.VariableName,

					    &var->var.VendorGuid,

					    &attributes, &datasize, NULL);

	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);



	if (status != EFI_BUFFER_TOO_SMALL)

		return efi_status_to_err(status);
@@ -832,12 +833,12 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf, 
	if (!data)

		return -ENOMEM;



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);

	status = efivars->ops->get_variable(var->var.VariableName,

					    &var->var.VendorGuid,

					    &attributes, &datasize,

					    (data + sizeof(attributes)));

	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);



	if (status != EFI_SUCCESS) {

		size = efi_status_to_err(status);
@@ -965,9 +966,9 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry, 
		goto out;



	kobject_uevent(&var->kobj, KOBJ_ADD);

	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);

	list_add(&var->list, &efivars->list);

	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);

	d_instantiate(dentry, inode);

	dget(dentry);

out:
@@ -984,7 +985,7 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry) 
	struct efivars *efivars = var->efivars;

	efi_status_t status;



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);



	status = efivars->ops->set_variable(var->var.VariableName,

					    &var->var.VendorGuid,
@@ -992,14 +993,14 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry) 


	if (status == EFI_SUCCESS || status == EFI_NOT_FOUND) {

		list_del(&var->list);

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		efivar_unregister(var);

		drop_nlink(dir);

		dput(dentry);

		return 0;

	}



	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);

	return -EINVAL;

};
@@ -1065,13 +1066,13 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent) 
		/* copied by the above to local storage in the dentry. */

		kfree(name);



		spin_lock(&efivars->lock);

		spin_lock_irq(&efivars->lock);

		efivars->ops->get_variable(entry->var.VariableName,

					   &entry->var.VendorGuid,

					   &entry->var.Attributes,

					   &size,

					   NULL);

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);



		mutex_lock(&inode->i_mutex);

		inode->i_private = entry;
@@ -1122,7 +1123,7 @@ 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;
@@ -1132,7 +1133,7 @@ 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;

}
@@ -1208,6 +1209,7 @@ static int efi_pstore_write(enum pstore_type_id type, 
	int i, ret = 0;

	u64 storage_space, remaining_space, max_variable_size;

	efi_status_t status = EFI_NOT_FOUND;

	unsigned long flags;



	if (pstore_cannot_block_path(reason)) {

		/*
@@ -1215,10 +1217,10 @@ static int efi_pstore_write(enum pstore_type_id type, 
		 * this driver returns without entering firmware to avoid

		 * hanging up.

		 */

		if (!spin_trylock(&efivars->lock))

		if (!spin_trylock_irqsave(&efivars->lock, flags))

			return -EBUSY;

	} else

		spin_lock(&efivars->lock);

		spin_lock_irqsave(&efivars->lock, flags);



	/*

	 * Check if there is a space enough to log.
@@ -1230,7 +1232,7 @@ static int efi_pstore_write(enum pstore_type_id type, 
						   &remaining_space,

						   &max_variable_size);

	if (status || remaining_space < size + DUMP_NAME_LEN * 2) {

		spin_unlock(&efivars->lock);

		spin_unlock_irqrestore(&efivars->lock, flags);

		*id = part;

		return -ENOSPC;

	}
@@ -1244,7 +1246,7 @@ 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 (size)

		ret = efivar_create_sysfs_entry(efivars,
@@ -1271,7 +1273,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count, 
	sprintf(name, "dump-type%u-%u-%d-%lu", type, (unsigned int)id, count,

		time.tv_sec);



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);



	for (i = 0; i < DUMP_NAME_LEN; i++)

		efi_name[i] = name[i];
@@ -1315,7 +1317,7 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count, 
	if (found)

		list_del(&found->list);



	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);



	if (found)

		efivar_unregister(found);
@@ -1385,7 +1387,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj, 
		return -EINVAL;

	}



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);



	/*

	 * Does this variable already exist?
@@ -1403,7 +1405,7 @@ static ssize_t efivar_create(struct file *filp, struct kobject *kobj, 
		}

	}

	if (found) {

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		return -EINVAL;

	}
@@ -1417,10 +1419,10 @@ 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_irq(&efivars->lock);

		return -EIO;

	}

	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);



	/* Create the entry in sysfs.  Locking is not required here */

	status = efivar_create_sysfs_entry(efivars,
@@ -1448,7 +1450,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj, 
	if (!capable(CAP_SYS_ADMIN))

		return -EACCES;



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);



	/*

	 * Does this variable already exist?
@@ -1466,7 +1468,7 @@ static ssize_t efivar_delete(struct file *filp, struct kobject *kobj, 
		}

	}

	if (!found) {

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		return -EINVAL;

	}

	/* force the Attributes/DataSize to 0 to ensure deletion */
@@ -1482,12 +1484,12 @@ 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_irq(&efivars->lock);

		return -EIO;

	}

	list_del(&search_efivar->list);

	/* We need to release this lock before unregistering. */

	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);

	efivar_unregister(search_efivar);



	/* It's dead Jim.... */
@@ -1602,9 +1604,9 @@ efivar_create_sysfs_entry(struct efivars *efivars, 
	kfree(short_name);

	short_name = NULL;



	spin_lock(&efivars->lock);

	spin_lock_irq(&efivars->lock);

	list_add(&new_efivar->list, &efivars->list);

	spin_unlock(&efivars->lock);

	spin_unlock_irq(&efivars->lock);



	return 0;

}
@@ -1673,9 +1675,9 @@ void unregister_efivars(struct efivars *efivars) 
	struct efivar_entry *entry, *n;



	list_for_each_entry_safe(entry, n, &efivars->list, list) {

		spin_lock(&efivars->lock);

		spin_lock_irq(&efivars->lock);

		list_del(&entry->list);

		spin_unlock(&efivars->lock);

		spin_unlock_irq(&efivars->lock);

		efivar_unregister(entry);

	}

	if (efivars->new_var)