2012-10-11 13:19:25

by Jeremy Kerr

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 <[email protected]>

---
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;

2012-10-11 13:42:49

by Matt Fleming

Subject: Re: [PATCH] efivarfs: Implement exclusive access for {get,set}_variable

On Thu, 2012-10-11 at 21:19 +0800, Jeremy Kerr wrote:
> 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 <[email protected]>
>
> ---
> drivers/firmware/efivars.c | 68 +++++++++++++++++++++++--------------
> 1 file changed, 43 insertions(+), 25 deletions(-)

Thanks, applied to 'next'.

2012-10-12 04:49:15

by Greg Kroah-Hartman

Subject: Re: [PATCH] efivarfs: Implement exclusive access for {get,set}_variable

On Thu, Oct 11, 2012 at 02:42:36PM +0100, Matt Fleming wrote:
> On Thu, 2012-10-11 at 21:19 +0800, Jeremy Kerr wrote:
> > 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 <[email protected]>
> >
> > ---
> > drivers/firmware/efivars.c | 68 +++++++++++++++++++++++--------------
> > 1 file changed, 43 insertions(+), 25 deletions(-)
>
> Thanks, applied to 'next'.

Should this be backported to the stable kernels?

thanks,

greg k-h

2012-10-12 05:04:18

by Jeremy Kerr

Subject: Re: [PATCH] efivarfs: Implement exclusive access for {get,set}_variable

Hi Greg,

> Should this be backported to the stable kernels?

No, the efivarfs code that this touches was only recently committed; it
won't be in any of the stable series.

Cheers,


Jeremy