4.15-stable review patch. If anyone has any objections, please let me know.
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From: Tom Herbert tom@quantonium.net
[ Upstream commit 2cc683e88c0c993ac3721d9b702cb0630abe2879 ]
Need to lock lower socket in order to provide mutual exclusion with kcm_unattach.
v2: Add Reported-by for syzbot
Fixes: ab7ac4eb9832e32a09f4e804 ("kcm: Kernel Connection Multiplexor module") Reported-by: syzbot+ea75c0ffcd353d32515f064aaebefc5279e6161e@syzkaller.appspotmail.com Signed-off-by: Tom Herbert tom@quantonium.net Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/kcm/kcmsock.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-)
--- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1381,24 +1381,32 @@ static int kcm_attach(struct socket *soc .parse_msg = kcm_parse_func_strparser, .read_sock_done = kcm_read_sock_done, }; - int err; + int err = 0;
csk = csock->sk; if (!csk) return -EINVAL;
+ lock_sock(csk); + /* Only allow TCP sockets to be attached for now */ if ((csk->sk_family != AF_INET && csk->sk_family != AF_INET6) || - csk->sk_protocol != IPPROTO_TCP) - return -EOPNOTSUPP; + csk->sk_protocol != IPPROTO_TCP) { + err = -EOPNOTSUPP; + goto out; + }
/* Don't allow listeners or closed sockets */ - if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE) - return -EOPNOTSUPP; + if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE) { + err = -EOPNOTSUPP; + goto out; + }
psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL); - if (!psock) - return -ENOMEM; + if (!psock) { + err = -ENOMEM; + goto out; + }
psock->mux = mux; psock->sk = csk; @@ -1407,7 +1415,7 @@ static int kcm_attach(struct socket *soc err = strp_init(&psock->strp, csk, &cb); if (err) { kmem_cache_free(kcm_psockp, psock); - return err; + goto out; }
write_lock_bh(&csk->sk_callback_lock); @@ -1419,7 +1427,8 @@ static int kcm_attach(struct socket *soc write_unlock_bh(&csk->sk_callback_lock); strp_done(&psock->strp); kmem_cache_free(kcm_psockp, psock); - return -EALREADY; + err = -EALREADY; + goto out; }
psock->save_data_ready = csk->sk_data_ready; @@ -1455,7 +1464,10 @@ static int kcm_attach(struct socket *soc /* Schedule RX work in case there are already bytes queued */ strp_check_rcv(&psock->strp);
- return 0; +out: + release_sock(csk); + + return err; }
static int kcm_attach_ioctl(struct socket *sock, struct kcm_attach *info) @@ -1507,6 +1519,7 @@ static void kcm_unattach(struct kcm_psoc
if (WARN_ON(psock->rx_kcm)) { write_unlock_bh(&csk->sk_callback_lock); + release_sock(csk); return; }