From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755861Ab2HQTmo (ORCPT ); Fri, 17 Aug 2012 15:42:44 -0400 Received: from usindpps03.hds.com ([207.126.252.16]:36488 "EHLO usindpps03.hds.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753801Ab2HQTmf convert rfc822-to-8bit (ORCPT ); Fri, 17 Aug 2012 15:42:35 -0400 From: Seiji Aguchi To: "linux-kernel@vger.kernel.org" , "Luck, Tony (tony.luck@intel.com)" , "mikew@google.com" , "Matthew Garrett (mjg@redhat.com)" , "dzickus@redhat.com" CC: "dle-develop@lists.sourceforge.net" , Satoru Moriya Subject: [RFC][PATCH 1/2] efivars: Disable external interrupt while holding efivars->lock Thread-Topic: [RFC][PATCH 1/2] efivars: Disable external interrupt while holding efivars->lock Thread-Index: Ac18sFlJoz2zbuxGTki/L0FDmmhr2w== Date: Fri, 17 Aug 2012 19:42:21 +0000 Message-ID: Accept-Language: ja-JP, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.74.43.113] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.7.7855,1.0.260,0.0.0000 definitions=2012-08-17_03:2012-08-17,2012-08-17,1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_policy_notspam policy=outbound_policy score=0 spamscore=0 ipscore=0 suspectscore=5 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=6.0.2-1203120001 definitions=main-1208170207 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [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 --- 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