From dc070cdb427e42a6b6b503427a029083e307ed34 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Fri, 22 Feb 2019 15:36:18 +0000 Subject: KEYS: always initialize keyring_index_key::desc_len commit ede0fa98a900e657d1fcd80b50920efc896c1a4c upstream. syzbot hit the 'BUG_ON(index_key->desc_len == 0);' in __key_link_begin() called from construct_alloc_key() during sys_request_key(), because the length of the key description was never calculated. The problem is that we rely on ->desc_len being initialized by search_process_keyrings(), specifically by search_nested_keyrings(). But, if the process isn't subscribed to any keyrings that never happens. Fix it by always initializing keyring_index_key::desc_len as soon as the description is set, like we already do in some places. The following program reproduces the BUG_ON() when it's run as root and no session keyring has been installed. If it doesn't work, try removing pam_keyinit.so from /etc/pam.d/login and rebooting. #include #include #include int main(void) { int id = add_key("keyring", "syz", NULL, 0, KEY_SPEC_USER_KEYRING); keyctl_setperm(id, KEY_OTH_WRITE); setreuid(5000, 5000); request_key("user", "desc", "", id); } Reported-by: syzbot+ec24e95ea483de0a24da@syzkaller.appspotmail.com Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring") Signed-off-by: Eric Biggers Signed-off-by: David Howells Cc: stable@vger.kernel.org Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- security/keys/request_key_auth.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'security/keys/request_key_auth.c') diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index ba74a0b4d1cb..f60baeb338e5 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -254,7 +254,7 @@ struct key *key_get_instantiation_authkey(key_serial_t target_id) struct key *authkey; key_ref_t authkey_ref; - sprintf(description, "%x", target_id); + ctx.index_key.desc_len = sprintf(description, "%x", target_id); authkey_ref = search_process_keyrings(&ctx); -- cgit v1.2.3