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Message-ID: <A5ED84D3BB3A384992CBB9C77DEDA4D41380007C@USINDEM103.corp.hds.com>
Date: Fri, 17 Aug 2012 19:42:21 +0000
From: Seiji Aguchi <seiji.aguchi@....com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
"mikew@...gle.com" <mikew@...gle.com>,
"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
"dzickus@...hat.com" <dzickus@...hat.com>
CC: "dle-develop@...ts.sourceforge.net"
<dle-develop@...ts.sourceforge.net>,
Satoru Moriya <satoru.moriya@....com>
Subject: [RFC][PATCH 1/2] efivars: Disable external interrupt while holding
efivars->lock
[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, they moved to a read callback
to pass a flags argument to spin_lock_irqsave/spin_unlock_irqrestore.
Even if spin_locks in open/close callbacks are erased, a whole process of open/read/close
is still serialized by psinfo->read_mutex which is taken in a pstore layer.
Also, initialization of efivars->walk_entry moved to a read callback to protect list_first_entry()
with efivars->lock. And some comments about efivars->walk_entry are added to avoid using it
without taking psinfo->read_mutex.
Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>
---
drivers/firmware/efivars.c | 66 ++++++++++++++++++++++++++-----------------
include/linux/efi.h | 3 ++
2 files changed, 43 insertions(+), 26 deletions(-)
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 47408e8..b6a813e 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",
@@ -630,19 +632,11 @@ efivar_unregister(struct efivar_entry *var)
static int efi_pstore_open(struct pstore_info *psi)
{
- struct efivars *efivars = psi->data;
-
- spin_lock(&efivars->lock);
- efivars->walk_entry = list_first_entry(&efivars->list,
- struct efivar_entry, list);
return 0;
}
static int efi_pstore_close(struct pstore_info *psi)
{
- struct efivars *efivars = psi->data;
-
- spin_unlock(&efivars->lock);
return 0;
}
@@ -656,6 +650,17 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
int i;
unsigned int part, size;
unsigned long time;
+ static unsigned long flags;
+
+ /*
+ * efivars->walk_entry is protected by pstore_info.read_mutex
+ */
+ if (!efivars->walk_entry) {
+ spin_lock_irqsave(&efivars->lock, flags);
+ efivars->walk_entry = list_first_entry(&efivars->list,
+ struct efivar_entry,
+ list);
+ }
while (&efivars->walk_entry->list != &efivars->list) {
if (!efi_guidcmp(efivars->walk_entry->var.VendorGuid,
@@ -682,6 +687,10 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
struct efivar_entry, list);
}
+
+ efivars->walk_entry = NULL;
+ spin_unlock_irqrestore(&efivars->lock, flags);
+
return 0;
}
@@ -696,11 +705,12 @@ 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 +748,7 @@ 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 +822,7 @@ 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 +833,7 @@ 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 +851,7 @@ 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 +865,10 @@ 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 +892,12 @@ 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 +915,7 @@ 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 +931,12 @@ 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 +1005,7 @@ 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 +1045,9 @@ 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 +1114,12 @@ 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)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 103adc6..f1f5703 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -649,6 +649,9 @@ struct efivars {
struct kset *kset;
struct bin_attribute *new_var, *del_var;
const struct efivar_operations *ops;
+ /*
+ * walk_entry is protected by pstore_info.read_mutex
+ */
struct efivar_entry *walk_entry;
struct pstore_info efi_pstore_info;
};
-- 1.7.1
--
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