From: David Howells Subject: [PATCH] KEYS: Fix bug in keyctl_session_to_parent() if parent has no session keyring Fix a bug in keyctl_session_to_parent() whereby it tries to check the ownership of the parent process's session keyring whether or not the parent has a session keyring [CVE-2010-2960]. A program like the following: #include #include int main(int argc, char **argv) { keyctl(KEYCTL_SESSION_TO_PARENT); } can be used to trigger the following bug report: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0 IP: [] keyctl_session_to_parent+0x251/0x443 ... Call Trace: [] ? keyctl_session_to_parent+0x67/0x443 [] ? __do_fault+0x24b/0x3d0 [] sys_keyctl+0xb4/0xb8 [] system_call_fastpath+0x16/0x1b if there is no parent process. If the system is using pam_keyinit then it mostly protected against this as all processes derived from a login will have inherited the session keyring created by pam_keyinit during the log in procedure. To test this, pam_keyinit calls need to be commented out in /etc/pam.d/. Signed-off-by: David Howells --- security/keys/keyctl.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 3868c67..60924f6 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -1305,7 +1305,8 @@ long keyctl_session_to_parent(void) goto not_permitted; /* the keyrings must have the same UID */ - if (pcred ->tgcred->session_keyring->uid != mycred->euid || + if ((pcred->tgcred->session_keyring && + pcred->tgcred->session_keyring->uid != mycred->euid) || mycred->tgcred->session_keyring->uid != mycred->euid) goto not_permitted;