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authorzhuoliang zhang <zhuoliang.zhang@mediatek.com>2020-10-23 09:05:35 +0200
committerSteffen Klassert <steffen.klassert@secunet.com>2020-10-23 09:08:55 +0200
commita779d91314ca7208b7feb3ad817b62904397c56d (patch)
treed5b4ad0fcb98fce613990b9466c65b33f4a82dd4 /net/xfrm
parent7fe94612dd4cfcd35fe0ec87745fb31ad2be71f8 (diff)
net: xfrm: fix a race condition during allocing spi
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>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_state.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index efc89a92961d..ee6ac32bb06d 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);