From 27777daa8b6df0c19aaf591d1536a586b3eb5e36 Mon Sep 17 00:00:00 2001 From: Jon Paul Maloy Date: Mon, 20 Jun 2016 09:20:46 -0400 Subject: tipc: unclone unbundled buffers before forwarding When extracting an individual message from a received "bundle" buffer, we just create a clone of the base buffer, and adjust it to point into the right position of the linearized data area of the latter. This works well for regular message reception, but during periods of extremely high load it may happen that an extracted buffer, e.g, a connection probe, is reversed and forwarded through an external interface while the preceding extracted message is still unhandled. When this happens, the header or data area of the preceding message will be partially overwritten by a MAC header, leading to unpredicatable consequences, such as a link reset. We now fix this by ensuring that the msg_reverse() function never returns a cloned buffer, and that the returned buffer always contains sufficient valid head and tail room to be forwarded. Reported-by: Erik Hugne Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller diff --git a/net/tipc/msg.c b/net/tipc/msg.c index 8740930..17201aa 100644 --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -41,6 +41,8 @@ #include "name_table.h" #define MAX_FORWARD_SIZE 1024 +#define BUF_HEADROOM (LL_MAX_HEADER + 48) +#define BUF_TAILROOM 16 static unsigned int align(unsigned int i) { @@ -505,6 +507,10 @@ bool tipc_msg_reverse(u32 own_node, struct sk_buff **skb, int err) msg_set_hdr_sz(hdr, BASIC_H_SIZE); } + if (skb_cloned(_skb) && + pskb_expand_head(_skb, BUF_HEADROOM, BUF_TAILROOM, GFP_KERNEL)) + goto exit; + /* Now reverse the concerned fields */ msg_set_errcode(hdr, err); msg_set_origport(hdr, msg_destport(&ohdr)); diff --git a/net/tipc/msg.h b/net/tipc/msg.h index 024da8a..7cf52fb 100644 --- a/net/tipc/msg.h +++ b/net/tipc/msg.h @@ -94,17 +94,6 @@ struct plist; #define TIPC_MEDIA_INFO_OFFSET 5 -/** - * TIPC message buffer code - * - * TIPC message buffer headroom reserves space for the worst-case - * link-level device header (in case the message is sent off-node). - * - * Note: Headroom should be a multiple of 4 to ensure the TIPC header fields - * are word aligned for quicker access - */ -#define BUF_HEADROOM (LL_MAX_HEADER + 48) - struct tipc_skb_cb { void *handle; struct sk_buff *tail; -- cgit v0.10.2