2.6.31-stable review patch. If anyone has any objections, please let us know. ------------------ From: David Howells commit 21279cfa107af07ef985539ac0de2152b9cba5f5 upstream. The destination keyring specified to request_key() and co. is made available to the process that instantiates the key (the slave process started by /sbin/request-key typically). This is passed in the request_key_auth struct as the dest_keyring member. keyctl_instantiate_key and keyctl_negate_key() call get_instantiation_keyring() to get the keyring to attach the newly constructed key to at the end of instantiation. This may be given a specific keyring into which a link will be made later, or it may be asked to find the keyring passed to request_key(). In the former case, it returns a keyring with the refcount incremented by lookup_user_key(); in the latter case, it returns the keyring from the request_key_auth struct - and does _not_ increment the refcount. The latter case will eventually result in an oops when the keyring prematurely runs out of references and gets destroyed. The effect may take some time to show up as the key is destroyed lazily. To fix this, the keyring returned by get_instantiation_keyring() must always have its refcount incremented, no matter where it comes from. This can be tested by setting /etc/request-key.conf to: #OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ... #====== ======= =============== =============== =============================== create * test:* * |/bin/false %u %g %d %{user:_display} negate * * * /bin/keyctl negate %k 10 @u and then doing: keyctl add user _display aaaaaaaa @u while keyctl request2 user test:x test:x @u && keyctl list @u; do keyctl request2 user test:x test:x @u; sleep 31; keyctl list @u; done which will oops eventually. Changing the negate line to have @u rather than %S at the end is important as that forces the latter case by passing a special keyring ID rather than an actual keyring ID. Reported-by: Alexander Zangerl Signed-off-by: David Howells Tested-by: Alexander Zangerl Signed-off-by: Linus Torvalds Cc: Chuck Ebbert Signed-off-by: Greg Kroah-Hartman --- security/keys/keyctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -860,7 +860,7 @@ static long get_instantiation_keyring(ke /* otherwise specify the destination keyring recorded in the * authorisation key (any KEY_SPEC_*_KEYRING) */ if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) { - *_dest_keyring = rka->dest_keyring; + *_dest_keyring = key_get(rka->dest_keyring); return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/