I figured out what's the root-cause of my panics.
In my case, for the stack shown in
http://marc.info/?l=linux-sparc&m=145610295109214&w=2
(which also has all the details about the issue),
tcp_make_synack has been called with attach_req set to true
so it sets up the skb->sk via:
if (attach_req) {
skb_set_owner_w(skb, req_to_sk(req));
} else { /* .. */
Now, req is a struct inet_request_sock, and we are casting this
as a struct sock, to later get the ->sk_policy[1] in the xfrm
code. Consider the sizes of these structures between 32 and 64 bits:
sizeof 32-bit 64-bit
-------------------------------------------
request_sock 256 312
inet_request_sock 272 328
sock 688 1216
And offsetof sk_policy[1] is 256 on the 32-bit v440, whereas
it is 520 on my 64-bit T5.
Thus on the v440, the sk_policy[1] is pointing at somewhere
in the middle of stuff set up by tcp_openreq_init() (the ireq
flags initialization).
Even on the 64-bit arch, trying to do req_to_sk(req) and accessing
fields beyond the sock_common, e.g., between offset 312 and 328
may not give you the fields you are looking for?
so how is this supposed to work? (Evidently it worked for Meelis
before, but I dont know if that was before or after commit
9e17f8a475).
--Sowmini
