Commit 23e390cd authored by KP Singh's avatar KP Singh Committed by James Morris
Browse files

security: Fix hook iteration and default value for inode_copy_up_xattr 



inode_copy_up_xattr returns 0 to indicate the acceptance of the xattr
and 1 to reject it. If the LSM does not know about the xattr, it's
expected to return -EOPNOTSUPP, which is the correct default value for
this hook. BPF LSM, currently, uses 0 as the default value and thereby
falsely allows all overlay fs xattributes to be copied up.

The iteration logic is also updated from the "bail-on-fail"
call_int_hook to continue on the non-decisive -EOPNOTSUPP and bail out
on other values.

Fixes: 98e828a0 ("security: Refactor declaration of LSM hooks")
Signed-off-by: default avatarKP Singh <kpsingh@google.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 4bc799dc

include/linux/lsm_hook_defs.h

+1 −1
Original line number Diff line number Diff line
@@ -150,7 +150,7 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer, 
	 size_t buffer_size)

LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)

LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)

LSM_HOOK(int, 0, inode_copy_up_xattr, const char *name)

LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name)

LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,

	 struct kernfs_node *kn)

LSM_HOOK(int, 0, file_permission, struct file *file, int mask)

security/security.c

+16 −1
Original line number Diff line number Diff line
@@ -1414,7 +1414,22 @@ EXPORT_SYMBOL(security_inode_copy_up); 


int security_inode_copy_up_xattr(const char *name)

{

	return call_int_hook(inode_copy_up_xattr, -EOPNOTSUPP, name);

	struct security_hook_list *hp;

	int rc;



	/*

	 * The implementation can return 0 (accept the xattr), 1 (discard the

	 * xattr), -EOPNOTSUPP if it does not know anything about the xattr or

	 * any other error code incase of an error.

	 */

	hlist_for_each_entry(hp,

		&security_hook_heads.inode_copy_up_xattr, list) {

		rc = hp->hook.inode_copy_up_xattr(name);

		if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr))

			return rc;

	}



	return LSM_RET_DEFAULT(inode_copy_up_xattr);

}

EXPORT_SYMBOL(security_inode_copy_up_xattr);

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