tipc: reassign pointers after skb reallocation / linearization

In tipc_msg_reverse(), we assign skb attributes to local pointers
in stack at startup. This is followed by skb_linearize() and for
cloned buffers we perform skb relocation using pskb_expand_head().
Both these methods may update the skb attributes and thus making
the pointers incorrect.

In this commit, we fix this error by ensuring that the pointers
are re-assigned after any of these skb operations.

Fixes: 29042e19f2c60 ("tipc: let function tipc_msg_reverse() expand header
when needed")
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/tipc/msg.c b/net/tipc/msg.c
index dcd90e6fa7c3..6ef379f004ac 100644
--- a/net/tipc/msg.c
+++ b/net/tipc/msg.c
@@ -479,13 +479,14 @@ bool tipc_msg_make_bundle(struct sk_buff **skb,  struct tipc_msg *msg,
 bool tipc_msg_reverse(u32 own_node,  struct sk_buff **skb, int err)
 {
         struct sk_buff *_skb = *skb;
-        struct tipc_msg *hdr = buf_msg(_skb);
+        struct tipc_msg *hdr;
         struct tipc_msg ohdr;
-        int dlen = min_t(uint, msg_data_sz(hdr), MAX_FORWARD_SIZE);
+        int dlen;
 
         if (skb_linearize(_skb))
                 goto exit;
         hdr = buf_msg(_skb);
+        dlen = min_t(uint, msg_data_sz(hdr), MAX_FORWARD_SIZE);
         if (msg_dest_droppable(hdr))
                 goto exit;
         if (msg_errcode(hdr))
@@ -511,6 +512,8 @@ bool tipc_msg_reverse(u32 own_node,  struct sk_buff **skb, int err)
             pskb_expand_head(_skb, BUF_HEADROOM, BUF_TAILROOM, GFP_ATOMIC))
                 goto exit;
 
+        /* reassign after skb header modifications */
+        hdr = buf_msg(_skb);
         /* Now reverse the concerned fields */
         msg_set_errcode(hdr, err);
         msg_set_non_seq(hdr, 0);