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e952837f3d
lookup and resize can run in parallel.
The xfrm_state_hash_generation seqlock ensures a retry, but the hash
functions can observe a hmask value that is too large for the new hlist
array.
rehash does:
rcu_assign_pointer(net->xfrm.state_bydst, ndst) [..]
net->xfrm.state_hmask = nhashmask;
While state lookup does:
h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family);
hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) {
This is only safe in case the update to state_bydst is larger than
net->xfrm.xfrm_state_hmask (or if the lookup function gets
serialized via state spinlock again).
Fix this by prefetching state_hmask and the associated pointers.
The xfrm_state_hash_generation seqlock retry will ensure that the pointer
and the hmask will be consistent.
The existing helpers, like xfrm_dst_hash(), are now unsafe for RCU side,
add lockdep assertions to document that they are only safe for insert
side.
xfrm_state_lookup_byaddr() uses the spinlock rather than RCU.
AFAICS this is an oversight from back when state lookup was converted to
RCU, this lock should be replaced with RCU in a future patch.
Reported-by: syzbot+5f9f31cb7d985f584d8e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/CACT4Y+azwfrE3uz6A5ZErov5YN2LYBN5KrsymBerT36VU8qzBA@mail.gmail.com/
Diagnosed-by: Dmitry Vyukov <dvyukov@google.com>
Fixes:
|
||
|---|---|---|
| .. | ||
| espintcp.c | ||
| Kconfig | ||
| Makefile | ||
| xfrm_algo.c | ||
| xfrm_compat.c | ||
| xfrm_device.c | ||
| xfrm_hash.c | ||
| xfrm_hash.h | ||
| xfrm_inout.h | ||
| xfrm_input.c | ||
| xfrm_interface_bpf.c | ||
| xfrm_interface_core.c | ||
| xfrm_ipcomp.c | ||
| xfrm_nat_keepalive.c | ||
| xfrm_output.c | ||
| xfrm_policy.c | ||
| xfrm_proc.c | ||
| xfrm_replay.c | ||
| xfrm_state_bpf.c | ||
| xfrm_state.c | ||
| xfrm_sysctl.c | ||
| xfrm_user.c | ||