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Date: Thu, 11 Oct 2012 21:19:11 +0800
From: Jeremy Kerr <jeremy.kerr@...onical.com>
To: Matt Fleming <matt.fleming@...el.com>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
Andy Whitcroft <apw@...onical.com>,
Matthew Garrett <mjg@...hat.com>
Subject: [PATCH] efivarfs: Implement exclusive access for {get,set}_variable
Currently, efivarfs does not enforce exclusion over the get_variable and
set_variable operations. Section 7.1 of UEFI requires us to only allow a
single processor to enter {get,set}_variable services at once.
This change acquires the efivars->lock over calls to these operations
from the efivarfs paths.
Signed-off-by: Jeremy Kerr <jeremy.kerr@...onical.com>
---
drivers/firmware/efivars.c | 68 +++++++++++++++++++++++--------------
1 file changed, 43 insertions(+), 25 deletions(-)
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 5765664..a86eb55 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -679,35 +679,45 @@ static ssize_t efivarfs_file_write(struct file *file,
goto out;
}
+ /*
+ * The lock here protects the get_variable call, the conditional
+ * set_variable call, and removal of the variable from the efivars
+ * list (in the case of an authenticated delete).
+ */
+ spin_lock(&efivars->lock);
+
status = efivars->ops->set_variable(var->var.VariableName,
&var->var.VendorGuid,
attributes, datasize,
data);
- switch (status) {
- case EFI_SUCCESS:
- break;
- case EFI_INVALID_PARAMETER:
- count = -EINVAL;
- goto out;
- case EFI_OUT_OF_RESOURCES:
- count = -ENOSPC;
- goto out;
- case EFI_DEVICE_ERROR:
- count = -EIO;
- goto out;
- case EFI_WRITE_PROTECTED:
- count = -EROFS;
- goto out;
- case EFI_SECURITY_VIOLATION:
- count = -EACCES;
- goto out;
- case EFI_NOT_FOUND:
- count = -ENOENT;
- goto out;
- default:
- count = -EINVAL;
- goto out;
+ if (status != EFI_SUCCESS) {
+ spin_unlock(&efivars->lock);
+ kfree(data);
+
+ switch (status) {
+ case EFI_INVALID_PARAMETER:
+ count = -EINVAL;
+ break;
+ case EFI_OUT_OF_RESOURCES:
+ count = -ENOSPC;
+ break;
+ case EFI_DEVICE_ERROR:
+ count = -EIO;
+ break;
+ case EFI_WRITE_PROTECTED:
+ count = -EROFS;
+ break;
+ case EFI_SECURITY_VIOLATION:
+ count = -EACCES;
+ break;
+ case EFI_NOT_FOUND:
+ count = -ENOENT;
+ break;
+ default:
+ count = -EINVAL;
+ }
+ return count;
}
/*
@@ -723,12 +733,12 @@ static ssize_t efivarfs_file_write(struct file *file,
NULL);
if (status == EFI_BUFFER_TOO_SMALL) {
+ spin_unlock(&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) {
- spin_lock(&efivars->lock);
list_del(&var->list);
spin_unlock(&efivars->lock);
efivar_unregister(var);
@@ -736,6 +746,7 @@ static ssize_t efivarfs_file_write(struct file *file,
dput(file->f_dentry);
} else {
+ spin_unlock(&efivars->lock);
pr_warn("efivarfs: inconsistent EFI variable implementation? "
"status = %lx\n", status);
}
@@ -757,9 +768,11 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
void *data;
ssize_t size = 0;
+ spin_lock(&efivars->lock);
status = efivars->ops->get_variable(var->var.VariableName,
&var->var.VendorGuid,
&attributes, &datasize, NULL);
+ spin_unlock(&efivars->lock);
if (status != EFI_BUFFER_TOO_SMALL)
return 0;
@@ -769,10 +782,13 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
if (!data)
return 0;
+ spin_lock(&efivars->lock);
status = efivars->ops->get_variable(var->var.VariableName,
&var->var.VendorGuid,
&attributes, &datasize,
(data + 4));
+ spin_unlock(&efivars->lock);
+
if (status != EFI_SUCCESS)
goto out_free;
@@ -993,11 +1009,13 @@ 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);
efivars->ops->get_variable(entry->var.VariableName,
&entry->var.VendorGuid,
&entry->var.Attributes,
&size,
NULL);
+ spin_unlock(&efivars->lock);
mutex_lock(&inode->i_mutex);
inode->i_private = entry;
--
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