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mirror of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-09-04 20:19:47 +08:00

sunrpc: fix handling of server side tls alerts

Scott Mayhew discovered a security exploit in NFS over TLS in
tls_alert_recv() due to its assumption it can read data from
the msg iterator's kvec..

kTLS implementation splits TLS non-data record payload between
the control message buffer (which includes the type such as TLS
aler or TLS cipher change) and the rest of the payload (say TLS
alert's level/description) which goes into the msg payload buffer.

This patch proposes to rework how control messages are setup and
used by sock_recvmsg().

If no control message structure is setup, kTLS layer will read and
process TLS data record types. As soon as it encounters a TLS control
message, it would return an error. At that point, NFS can setup a
kvec backed msg buffer and read in the control message such as a
TLS alert. Msg iterator can advance the kvec pointer as a part of
the copy process thus we need to revert the iterator before calling
into the tls_alert_recv.

Reported-by: Scott Mayhew <smayhew@redhat.com>
Fixes: 5e052dda12 ("SUNRPC: Recognize control messages in server-side TCP socket code")
Suggested-by: Trond Myklebust <trondmy@hammerspace.com>
Cc: stable@vger.kernel.org
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Olga Kornievskaia 2025-07-29 12:40:20 -04:00 committed by Chuck Lever
parent e5a7315077
commit bee47cb026

View File

@ -257,20 +257,47 @@ svc_tcp_sock_process_cmsg(struct socket *sock, struct msghdr *msg,
} }
static int static int
svc_tcp_sock_recv_cmsg(struct svc_sock *svsk, struct msghdr *msg) svc_tcp_sock_recv_cmsg(struct socket *sock, unsigned int *msg_flags)
{ {
union { union {
struct cmsghdr cmsg; struct cmsghdr cmsg;
u8 buf[CMSG_SPACE(sizeof(u8))]; u8 buf[CMSG_SPACE(sizeof(u8))];
} u; } u;
struct socket *sock = svsk->sk_sock; u8 alert[2];
struct kvec alert_kvec = {
.iov_base = alert,
.iov_len = sizeof(alert),
};
struct msghdr msg = {
.msg_flags = *msg_flags,
.msg_control = &u,
.msg_controllen = sizeof(u),
};
int ret; int ret;
msg->msg_control = &u; iov_iter_kvec(&msg.msg_iter, ITER_DEST, &alert_kvec, 1,
msg->msg_controllen = sizeof(u); alert_kvec.iov_len);
ret = sock_recvmsg(sock, &msg, MSG_DONTWAIT);
if (ret > 0 &&
tls_get_record_type(sock->sk, &u.cmsg) == TLS_RECORD_TYPE_ALERT) {
iov_iter_revert(&msg.msg_iter, ret);
ret = svc_tcp_sock_process_cmsg(sock, &msg, &u.cmsg, -EAGAIN);
}
return ret;
}
static int
svc_tcp_sock_recvmsg(struct svc_sock *svsk, struct msghdr *msg)
{
int ret;
struct socket *sock = svsk->sk_sock;
ret = sock_recvmsg(sock, msg, MSG_DONTWAIT); ret = sock_recvmsg(sock, msg, MSG_DONTWAIT);
if (unlikely(msg->msg_controllen != sizeof(u))) if (msg->msg_flags & MSG_CTRUNC) {
ret = svc_tcp_sock_process_cmsg(sock, msg, &u.cmsg, ret); msg->msg_flags &= ~(MSG_CTRUNC | MSG_EOR);
if (ret == 0 || ret == -EIO)
ret = svc_tcp_sock_recv_cmsg(sock, &msg->msg_flags);
}
return ret; return ret;
} }
@ -321,7 +348,7 @@ static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen,
iov_iter_advance(&msg.msg_iter, seek); iov_iter_advance(&msg.msg_iter, seek);
buflen -= seek; buflen -= seek;
} }
len = svc_tcp_sock_recv_cmsg(svsk, &msg); len = svc_tcp_sock_recvmsg(svsk, &msg);
if (len > 0) if (len > 0)
svc_flush_bvec(bvec, len, seek); svc_flush_bvec(bvec, len, seek);
@ -1018,7 +1045,7 @@ static ssize_t svc_tcp_read_marker(struct svc_sock *svsk,
iov.iov_base = ((char *)&svsk->sk_marker) + svsk->sk_tcplen; iov.iov_base = ((char *)&svsk->sk_marker) + svsk->sk_tcplen;
iov.iov_len = want; iov.iov_len = want;
iov_iter_kvec(&msg.msg_iter, ITER_DEST, &iov, 1, want); iov_iter_kvec(&msg.msg_iter, ITER_DEST, &iov, 1, want);
len = svc_tcp_sock_recv_cmsg(svsk, &msg); len = svc_tcp_sock_recvmsg(svsk, &msg);
if (len < 0) if (len < 0)
return len; return len;
svsk->sk_tcplen += len; svsk->sk_tcplen += len;