From: R. Parameswaran <[email protected]> commit 57240d007816486131bee88cd474c2a71f0fe224 upstream.
The MTU overhead calculation in L2TP device set-up merged via commit b784e7ebfce8cfb16c6f95e14e8532d0768ab7ff needs to be adjusted to lock the tunnel socket while referencing the sub-data structures to derive the socket's IP overhead. Reported-by: Guillaume Nault <[email protected]> Tested-by: Guillaume Nault <[email protected]> Signed-off-by: R. Parameswaran <[email protected]> Signed-off-by: David S. Miller <[email protected]> Cc: Giuliano Procida <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- include/linux/net.h | 2 +- net/l2tp/l2tp_eth.c | 2 ++ net/socket.c | 2 +- 3 files changed, 4 insertions(+), 2 deletions(-) --- a/include/linux/net.h +++ b/include/linux/net.h @@ -298,7 +298,7 @@ int kernel_sendpage(struct socket *sock, int kernel_sock_ioctl(struct socket *sock, int cmd, unsigned long arg); int kernel_sock_shutdown(struct socket *sock, enum sock_shutdown_cmd how); -/* Following routine returns the IP overhead imposed by a socket. */ +/* Routine returns the IP overhead imposed by a (caller-protected) socket. */ u32 kernel_sock_ip_overhead(struct sock *sk); #define MODULE_ALIAS_NETPROTO(proto) \ --- a/net/l2tp/l2tp_eth.c +++ b/net/l2tp/l2tp_eth.c @@ -240,7 +240,9 @@ static void l2tp_eth_adjust_mtu(struct l dev->needed_headroom += session->hdr_len; return; } + lock_sock(tunnel->sock); l3_overhead = kernel_sock_ip_overhead(tunnel->sock); + release_sock(tunnel->sock); if (l3_overhead == 0) { /* L3 Overhead couldn't be identified, this could be * because tunnel->sock was NULL or the socket's --- a/net/socket.c +++ b/net/socket.c @@ -3325,7 +3325,7 @@ EXPORT_SYMBOL(kernel_sock_shutdown); /* This routine returns the IP overhead imposed by a socket i.e. * the length of the underlying IP header, depending on whether * this is an IPv4 or IPv6 socket and the length from IP options turned - * on at the socket. + * on at the socket. Assumes that the caller has a lock on the socket. */ u32 kernel_sock_ip_overhead(struct sock *sk) {
