evm: fix potential race when removing xattrs
EVM needs to be atomically updated when removing xattrs.
Otherwise concurrent EVM verification may fail in between.
This patch fixes by moving i_mutex unlocking after calling
EVM hook. fsnotify_xattr() is also now called while locked
the same way as it is done in __vfs_setxattr_noperm.
Changelog:
- remove unused 'inode' variable.
Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
diff --git a/fs/xattr.c b/fs/xattr.c
index 4ef6985..072fee1 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -298,18 +298,18 @@
mutex_lock(&inode->i_mutex);
error = security_inode_removexattr(dentry, name);
- if (error) {
- mutex_unlock(&inode->i_mutex);
- return error;
- }
+ if (error)
+ goto out;
error = inode->i_op->removexattr(dentry, name);
- mutex_unlock(&inode->i_mutex);
if (!error) {
fsnotify_xattr(dentry);
evm_inode_post_removexattr(dentry, name);
}
+
+out:
+ mutex_unlock(&inode->i_mutex);
return error;
}
EXPORT_SYMBOL_GPL(vfs_removexattr);
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 5820914..1334e02 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -387,17 +387,16 @@
* @xattr_name: pointer to the affected extended attribute name
*
* Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
+ *
+ * No need to take the i_mutex lock here, as this function is called from
+ * vfs_removexattr() which takes the i_mutex.
*/
void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
{
- struct inode *inode = d_backing_inode(dentry);
-
if (!evm_initialized || !evm_protected_xattr(xattr_name))
return;
- mutex_lock(&inode->i_mutex);
evm_update_evmxattr(dentry, xattr_name, NULL, 0);
- mutex_unlock(&inode->i_mutex);
}
/**