From: zhuoliang zhang zhuoliang.zhang@mediatek.com
[ Upstream commit a779d91314ca7208b7feb3ad817b62904397c56d ]
we found that the following race condition exists in xfrm_alloc_userspi flow:
user thread state_hash_work thread ---- ---- xfrm_alloc_userspi() __find_acq_core() /*alloc new xfrm_state:x*/ xfrm_state_alloc() /*schedule state_hash_work thread*/ xfrm_hash_grow_check() xfrm_hash_resize() xfrm_alloc_spi /*hold lock*/ x->id.spi = htonl(spi) spin_lock_bh(&net->xfrm.xfrm_state_lock) /*waiting lock release*/ xfrm_hash_transfer() spin_lock_bh(&net->xfrm.xfrm_state_lock) /*add x into hlist:net->xfrm.state_byspi*/ hlist_add_head_rcu(&x->byspi) spin_unlock_bh(&net->xfrm.xfrm_state_lock)
/*add x into hlist:net->xfrm.state_byspi 2 times*/ hlist_add_head_rcu(&x->byspi)
1. a new state x is alloced in xfrm_state_alloc() and added into the bydst hlist in __find_acq_core() on the LHS; 2. on the RHS, state_hash_work thread travels the old bydst and tranfers every xfrm_state (include x) into the new bydst hlist and new byspi hlist; 3. user thread on the LHS gets the lock and adds x into the new byspi hlist again.
So the same xfrm_state (x) is added into the same list_hash (net->xfrm.state_byspi) 2 times that makes the list_hash become an inifite loop.
To fix the race, x->id.spi = htonl(spi) in the xfrm_alloc_spi() is moved to the back of spin_lock_bh, sothat state_hash_work thread no longer add x which id.spi is zero into the hash_list.
Fixes: f034b5d4efdf ("[XFRM]: Dynamic xfrm_state hash table sizing.") Signed-off-by: zhuoliang zhang zhuoliang.zhang@mediatek.com Acked-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/xfrm/xfrm_state.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index efc89a92961df..ee6ac32bb06d7 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -2004,6 +2004,7 @@ int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high) int err = -ENOENT; __be32 minspi = htonl(low); __be32 maxspi = htonl(high); + __be32 newspi = 0; u32 mark = x->mark.v & x->mark.m;
spin_lock_bh(&x->lock); @@ -2022,21 +2023,22 @@ int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high) xfrm_state_put(x0); goto unlock; } - x->id.spi = minspi; + newspi = minspi; } else { u32 spi = 0; for (h = 0; h < high-low+1; h++) { spi = low + prandom_u32()%(high-low+1); x0 = xfrm_state_lookup(net, mark, &x->id.daddr, htonl(spi), x->id.proto, x->props.family); if (x0 == NULL) { - x->id.spi = htonl(spi); + newspi = htonl(spi); break; } xfrm_state_put(x0); } } - if (x->id.spi) { + if (newspi) { spin_lock_bh(&net->xfrm.xfrm_state_lock); + x->id.spi = newspi; h = xfrm_spi_hash(net, &x->id.daddr, x->id.spi, x->id.proto, x->props.family); hlist_add_head_rcu(&x->byspi, net->xfrm.state_byspi + h); spin_unlock_bh(&net->xfrm.xfrm_state_lock);