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net: xfrm: fix a race condition during allocing spi
[ Upstream commita779d91314
] 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:f034b5d4ef
("[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>
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parent
6fb1e4eceb
commit
4cf755e9bc
1 changed files with 5 additions and 3 deletions
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@ -1783,6 +1783,7 @@ int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high)
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int err = -ENOENT;
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__be32 minspi = htonl(low);
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__be32 maxspi = htonl(high);
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__be32 newspi = 0;
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u32 mark = x->mark.v & x->mark.m;
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spin_lock_bh(&x->lock);
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@ -1801,21 +1802,22 @@ int xfrm_alloc_spi(struct xfrm_state *x, u32 low, u32 high)
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xfrm_state_put(x0);
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goto unlock;
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}
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x->id.spi = minspi;
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newspi = minspi;
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} else {
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u32 spi = 0;
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for (h = 0; h < high-low+1; h++) {
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spi = low + prandom_u32()%(high-low+1);
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x0 = xfrm_state_lookup(net, mark, &x->id.daddr, htonl(spi), x->id.proto, x->props.family);
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if (x0 == NULL) {
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x->id.spi = htonl(spi);
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newspi = htonl(spi);
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break;
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}
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xfrm_state_put(x0);
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}
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}
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if (x->id.spi) {
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if (newspi) {
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spin_lock_bh(&net->xfrm.xfrm_state_lock);
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x->id.spi = newspi;
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h = xfrm_spi_hash(net, &x->id.daddr, x->id.spi, x->id.proto, x->props.family);
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hlist_add_head_rcu(&x->byspi, net->xfrm.state_byspi + h);
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spin_unlock_bh(&net->xfrm.xfrm_state_lock);
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