From b10b9c342f7571f287fd422be5d5c0beb26ba974 Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Mon, 10 Oct 2022 12:31:21 -0400 Subject: lsm: make security_socket_getpeersec_stream() sockptr_t safe Commit 4ff09db1b79b ("bpf: net: Change sk_getsockopt() to take the sockptr_t argument") made it possible to call sk_getsockopt() with both user and kernel address space buffers through the use of the sockptr_t type. Unfortunately at the time of conversion the security_socket_getpeersec_stream() LSM hook was written to only accept userspace buffers, and in a desire to avoid having to change the LSM hook the commit author simply passed the sockptr_t's userspace buffer pointer. Since the only sk_getsockopt() callers at the time of conversion which used kernel sockptr_t buffers did not allow SO_PEERSEC, and hence the security_socket_getpeersec_stream() hook, this was acceptable but also very fragile as future changes presented the possibility of silently passing kernel space pointers to the LSM hook. There are several ways to protect against this, including careful code review of future commits, but since relying on code review to catch bugs is a recipe for disaster and the upstream eBPF maintainer is "strongly against defensive programming", this patch updates the LSM hook, and all of the implementations to support sockptr_t and safely handle both user and kernel space buffers. Acked-by: Casey Schaufler Acked-by: John Johansen Signed-off-by: Paul Moore --- security/smack/smack_lsm.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) (limited to 'security/smack/smack_lsm.c') diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index b6306d71c908..2bd7fadf7fb4 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4006,12 +4006,12 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb) * returns zero on success, an error code otherwise */ static int smack_socket_getpeersec_stream(struct socket *sock, - char __user *optval, - int __user *optlen, unsigned len) + sockptr_t optval, sockptr_t optlen, + unsigned int len) { struct socket_smack *ssp; char *rcp = ""; - int slen = 1; + u32 slen = 1; int rc = 0; ssp = sock->sk->sk_security; @@ -4019,15 +4019,16 @@ static int smack_socket_getpeersec_stream(struct socket *sock, rcp = ssp->smk_packet->smk_known; slen = strlen(rcp) + 1; } - - if (slen > len) + if (slen > len) { rc = -ERANGE; - else if (copy_to_user(optval, rcp, slen) != 0) - rc = -EFAULT; + goto out_len; + } - if (put_user(slen, optlen) != 0) + if (copy_to_sockptr(optval, rcp, slen)) + rc = -EFAULT; +out_len: + if (copy_to_sockptr(optlen, &slen, sizeof(slen))) rc = -EFAULT; - return rc; } -- cgit v1.2.3