commit c9f838d104fed6f2f61d68164712e3204bf5271b upstream.
This fixes CVE-2017-7472.
Running the following program as an unprivileged user exhausts kernel
memory by leaking thread keyrings:
#include <keyutils.h>
int main()
{
for (;;)
keyctl_set_reqkey_keyring(KEY_REQKEY_DEFL_THREAD_KEYRING);
}
Fix it by only creating a new thread keyring if there wasn't one before.
To make things more consistent, make install_thread_keyring_to_cred()
and install_process_keyring_to_cred() both return 0 if the corresponding
keyring is already present.
Fixes: d84f4f992c ("CRED: Inaugurate COW credentials")
Change-Id: I130899d7dc35d88d7763466d64fb99fa8084c8cd
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
c07b9a0eac