[PATCH 3.4 143/214] efivars: Disable external interrupt while holding efivars->lock

Greg Kroah-Hartman
2014-06-05T04:21:42Z

From: Josh Boyer <jwboyer@redhat.com>

commit 81fa4e581d9283f7992a0d8c534bb141eb840a14 upstream.

[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: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Mike Waychison <mikew@google.com>
Acked-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
[bwh: Backported to 3.2:
- Drop efivarfs changes
- Adjust context
- Drop change to efi_pstore_erase(), which is implemented using
efi_pstore_write() here]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/firmware/efivars.c | 44 +++++++++++++++++++++++---------------------
1 file changed, 23 insertions(+), 21 deletions(-)

--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -396,10 +396,11 @@ 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",
@@ -528,14 +529,14 @@ efivar_store_raw(struct efivar_entry *en
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",
@@ -646,7 +647,7 @@ static int efi_pstore_open(struct pstore
{
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;
@@ -656,7 +657,7 @@ static int efi_pstore_close(struct pstor
{
struct efivars *efivars = psi->data;

- spin_unlock(&efivars->lock);
+ spin_unlock_irq(&efivars->lock);
return 0;
}

@@ -712,11 +713,12 @@ static int efi_pstore_write(enum pstore_
int i, ret = 0;
u64 storage_space, remaining_space, max_variable_size;
efi_status_t status = EFI_NOT_FOUND;
+ 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);

/*
* Check if there is a space enough to log.
@@ -728,7 +730,7 @@ static int efi_pstore_write(enum pstore_
&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;
}
@@ -769,7 +771,7 @@ static int efi_pstore_write(enum pstore_
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);
@@ -853,7 +855,7 @@ static ssize_t efivar_create(struct file
return -EINVAL;
}

- spin_lock(&efivars->lock);
+ spin_lock_irq(&efivars->lock);

/*
* Does this variable already exist?
@@ -871,7 +873,7 @@ static ssize_t efivar_create(struct file
}
}
if (found) {
- spin_unlock(&efivars->lock);
+ spin_unlock_irq(&efivars->lock);
return -EINVAL;
}

@@ -885,10 +887,10 @@ static ssize_t efivar_create(struct file
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,
@@ -916,7 +918,7 @@ static ssize_t efivar_delete(struct file
if (!capable(CAP_SYS_ADMIN))
return -EACCES;

- spin_lock(&efivars->lock);
+ spin_lock_irq(&efivars->lock);

/*
* Does this variable already exist?
@@ -934,7 +936,7 @@ static ssize_t efivar_delete(struct file
}
}
if (!found) {
- spin_unlock(&efivars->lock);
+ spin_unlock_irq(&efivars->lock);
return -EINVAL;
}
/* force the Attributes/DataSize to 0 to ensure deletion */
@@ -950,12 +952,12 @@ static ssize_t efivar_delete(struct file
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.... */
@@ -1110,9 +1112,9 @@ efivar_create_sysfs_entry(struct 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;
}
@@ -1181,9 +1183,9 @@ void unregister_efivars(struct 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)