evm: remove evm_xattr_acl_change()

The security and integrity infrastructure has dedicated hooks now so
evm_xattr_acl_change() is dead code. Before this commit the callchain was:

evm_protect_xattr()
-> evm_xattr_change()
   -> evm_xattr_acl_change()

where evm_protect_xattr() was hit from evm_inode_setxattr() and
evm_inode_removexattr(). But now we have evm_inode_set_acl() and
evm_inode_remove_acl() and have switched over the vfs to rely on the posix
acl api so the code isn't hit anymore.

Suggested-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index dcc5e704ef70a07ec7fb7fa9f64668321873ccbe..e074c2b4d499989a6701d8a51d623890158c9d67 100644 (file)
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -434,66 +434,6 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
        return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
 }
 
-/*
- * evm_xattr_acl_change - check if passed ACL changes the inode mode
- * @mnt_userns: user namespace of the idmapped mount
- * @dentry: pointer to the affected dentry
- * @xattr_name: requested xattr
- * @xattr_value: requested xattr value
- * @xattr_value_len: requested xattr value length
- *
- * Check if passed ACL changes the inode mode, which is protected by EVM.
- *
- * Returns 1 if passed ACL causes inode mode change, 0 otherwise.
- */
-static int evm_xattr_acl_change(struct user_namespace *mnt_userns,
-                               struct dentry *dentry, const char *xattr_name,
-                               const void *xattr_value, size_t xattr_value_len)
-{
-#ifdef CONFIG_FS_POSIX_ACL
-       umode_t mode;
-       struct posix_acl *acl = NULL, *acl_res;
-       struct inode *inode = d_backing_inode(dentry);
-       int rc;
-
-       /*
-        * An earlier comment here mentioned that the idmappings for
-        * ACL_{GROUP,USER} don't matter since EVM is only interested in the
-        * mode stored as part of POSIX ACLs. Nonetheless, if it must translate
-        * from the uapi POSIX ACL representation to the VFS internal POSIX ACL
-        * representation it should do so correctly. There's no guarantee that
-        * we won't change POSIX ACLs in a way that ACL_{GROUP,USER} matters
-        * for the mode at some point and it's difficult to keep track of all
-        * the LSM and integrity modules and what they do to POSIX ACLs.
-        *
-        * Frankly, EVM shouldn't try to interpret the uapi struct for POSIX
-        * ACLs it received. It requires knowledge that only the VFS is
-        * guaranteed to have.
-        */
-       acl = vfs_set_acl_prepare(mnt_userns, i_user_ns(inode),
-                                 xattr_value, xattr_value_len);
-       if (IS_ERR_OR_NULL(acl))
-               return 1;
-
-       acl_res = acl;
-       /*
-        * Passing mnt_userns is necessary to correctly determine the GID in
-        * an idmapped mount, as the GID is used to clear the setgid bit in
-        * the inode mode.
-        */
-       rc = posix_acl_update_mode(mnt_userns, inode, &mode, &acl_res);
-
-       posix_acl_release(acl);
-
-       if (rc)
-               return 1;
-
-       if (inode->i_mode != mode)
-               return 1;
-#endif
-       return 0;
-}
-
 /*
  * evm_xattr_change - check if passed xattr value differs from current value
  * @mnt_userns: user namespace of the idmapped mount
@@ -513,10 +453,6 @@ static int evm_xattr_change(struct user_namespace *mnt_userns,
        char *xattr_data = NULL;
        int rc = 0;
 
-       if (posix_xattr_acl(xattr_name))
-               return evm_xattr_acl_change(mnt_userns, dentry, xattr_name,
-                                           xattr_value, xattr_value_len);
-
        rc = vfs_getxattr_alloc(&init_user_ns, dentry, xattr_name, &xattr_data,
                                0, GFP_NOFS);
        if (rc < 0)