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efi: Handle deletions and size changes in efivarfs_write_file 

A write to an efivarfs file will not always result in a variable of
'count' size after the EFI SetVariable() call. We may have appended to
the existing data (ie, with the EFI_VARIABLE_APPEND_WRITE attribute), or
even have deleted the variable (with an authenticated variable update,
with a zero datasize).

This change re-reads the updated variable from firmware, to check for
size changes and deletions. In the latter case, we need to drop the
dentry.

Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
This commit is contained in:
Jeremy Kerr 2012-10-05 13:54:56 +08:00 committed by Matt Fleming
parent 5d9db88376
commit 0c542edde3
1 changed files with 39 additions and 10 deletions
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49
drivers/firmware/efivars.c
View File

@ -658,6 +658,7 @@ static ssize_t efivarfs_file_write(struct file *file,
u32 attributes;
struct inode *inode = file->f_mapping->host;
int datasize = count - sizeof(attributes);
unsigned long newdatasize;
if (count < sizeof(attributes))
return -EINVAL;
@ -696,32 +697,60 @@ static ssize_t efivarfs_file_write(struct file *file,
switch (status) {
case EFI_SUCCESS:
mutex_lock(&inode->i_mutex);
i_size_write(inode, count);
mutex_unlock(&inode->i_mutex);
break;
case EFI_INVALID_PARAMETER:
count = -EINVAL;
break;
goto out;
case EFI_OUT_OF_RESOURCES:
count = -ENOSPC;
break;
goto out;
case EFI_DEVICE_ERROR:
count = -EIO;
break;
goto out;
case EFI_WRITE_PROTECTED:
count = -EROFS;
break;
goto out;
case EFI_SECURITY_VIOLATION:
count = -EACCES;
break;
goto out;
case EFI_NOT_FOUND:
count = -ENOENT;
break;
goto out;
default:
count = -EINVAL;
break;
goto out;
}
/*
* Writing to the variable may have caused a change in size (which
* could either be an append or an overwrite), or the variable to be
* deleted. Perform a GetVariable() so we can tell what actually
* happened.
*/
newdatasize = 0;
status = efivars->ops->get_variable(var->var.VariableName,
&var->var.VendorGuid,
NULL, &newdatasize,
NULL);
if (status == EFI_BUFFER_TOO_SMALL) {
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);
drop_nlink(inode);
dput(file->f_dentry);
} else {
pr_warn("efivarfs: inconsistent EFI variable implementation? "
"status = %lx\n", status);
}
out:
kfree(data);