Commit e952837f authored by Florian Westphal's avatar Florian Westphal Committed by Steffen Klassert
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xfrm: state: fix out-of-bounds read during lookup 



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: default avatar <syzbot+5f9f31cb7d985f584d8e@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/netdev/CACT4Y+azwfrE3uz6A5ZErov5YN2LYBN5KrsymBerT36VU8qzBA@mail.gmail.com/


Diagnosed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Fixes: c2f672fc ("xfrm: state lookup can be lockless")
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent c05c5e5a

net/xfrm/xfrm_state.c

+70 −19
Original line number Diff line number Diff line
@@ -34,6 +34,8 @@ 


#define xfrm_state_deref_prot(table, net) \

	rcu_dereference_protected((table), lockdep_is_held(&(net)->xfrm.xfrm_state_lock))

#define xfrm_state_deref_check(table, net) \

	rcu_dereference_check((table), lockdep_is_held(&(net)->xfrm.xfrm_state_lock))



static void xfrm_state_gc_task(struct work_struct *work);
@@ -62,6 +64,8 @@ static inline unsigned int xfrm_dst_hash(struct net *net, 
					 u32 reqid,

					 unsigned short family)

{

	lockdep_assert_held(&net->xfrm.xfrm_state_lock);



	return __xfrm_dst_hash(daddr, saddr, reqid, family, net->xfrm.state_hmask);

}
@@ -70,6 +74,8 @@ static inline unsigned int xfrm_src_hash(struct net *net, 
					 const xfrm_address_t *saddr,

					 unsigned short family)

{

	lockdep_assert_held(&net->xfrm.xfrm_state_lock);



	return __xfrm_src_hash(daddr, saddr, family, net->xfrm.state_hmask);

}
@@ -77,11 +83,15 @@ static inline unsigned int 
xfrm_spi_hash(struct net *net, const xfrm_address_t *daddr,

	      __be32 spi, u8 proto, unsigned short family)

{

	lockdep_assert_held(&net->xfrm.xfrm_state_lock);



	return __xfrm_spi_hash(daddr, spi, proto, family, net->xfrm.state_hmask);

}



static unsigned int xfrm_seq_hash(struct net *net, u32 seq)

{

	lockdep_assert_held(&net->xfrm.xfrm_state_lock);



	return __xfrm_seq_hash(seq, net->xfrm.state_hmask);

}
@@ -1041,16 +1051,38 @@ xfrm_init_tempstate(struct xfrm_state *x, const struct flowi *fl, 
	x->props.family = tmpl->encap_family;

}



static struct xfrm_state *__xfrm_state_lookup_all(struct net *net, u32 mark,

struct xfrm_hash_state_ptrs {

	const struct hlist_head *bydst;

	const struct hlist_head *bysrc;

	const struct hlist_head *byspi;

	unsigned int hmask;

};



static void xfrm_hash_ptrs_get(const struct net *net, struct xfrm_hash_state_ptrs *ptrs)

{

	unsigned int sequence;



	do {

		sequence = read_seqcount_begin(&net->xfrm.xfrm_state_hash_generation);



		ptrs->bydst = xfrm_state_deref_check(net->xfrm.state_bydst, net);

		ptrs->bysrc = xfrm_state_deref_check(net->xfrm.state_bysrc, net);

		ptrs->byspi = xfrm_state_deref_check(net->xfrm.state_byspi, net);

		ptrs->hmask = net->xfrm.state_hmask;

	} while (read_seqcount_retry(&net->xfrm.xfrm_state_hash_generation, sequence));

}



static struct xfrm_state *__xfrm_state_lookup_all(const struct xfrm_hash_state_ptrs *state_ptrs,

						  u32 mark,

						  const xfrm_address_t *daddr,

						  __be32 spi, u8 proto,

						  unsigned short family,

						  struct xfrm_dev_offload *xdo)

{

	unsigned int h = xfrm_spi_hash(net, daddr, spi, proto, family);

	unsigned int h = __xfrm_spi_hash(daddr, spi, proto, family, state_ptrs->hmask);

	struct xfrm_state *x;



	hlist_for_each_entry_rcu(x, net->xfrm.state_byspi + h, byspi) {

	hlist_for_each_entry_rcu(x, state_ptrs->byspi + h, byspi) {

#ifdef CONFIG_XFRM_OFFLOAD

		if (xdo->type == XFRM_DEV_OFFLOAD_PACKET) {

			if (x->xso.type != XFRM_DEV_OFFLOAD_PACKET)
@@ -1084,15 +1116,16 @@ static struct xfrm_state *__xfrm_state_lookup_all(struct net *net, u32 mark, 
	return NULL;

}



static struct xfrm_state *__xfrm_state_lookup(struct net *net, u32 mark,

static struct xfrm_state *__xfrm_state_lookup(const struct xfrm_hash_state_ptrs *state_ptrs,

					      u32 mark,

					      const xfrm_address_t *daddr,

					      __be32 spi, u8 proto,

					      unsigned short family)

{

	unsigned int h = xfrm_spi_hash(net, daddr, spi, proto, family);

	unsigned int h = __xfrm_spi_hash(daddr, spi, proto, family, state_ptrs->hmask);

	struct xfrm_state *x;



	hlist_for_each_entry_rcu(x, net->xfrm.state_byspi + h, byspi) {

	hlist_for_each_entry_rcu(x, state_ptrs->byspi + h, byspi) {

		if (x->props.family != family ||

		    x->id.spi       != spi ||

		    x->id.proto     != proto ||
@@ -1114,6 +1147,7 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark, 
					   __be32 spi, u8 proto,

					   unsigned short family)

{

	struct xfrm_hash_state_ptrs state_ptrs;

	struct hlist_head *state_cache_input;

	struct xfrm_state *x = NULL;

	int cpu = get_cpu();
@@ -1135,7 +1169,9 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark, 
		goto out;

	}



	x = __xfrm_state_lookup(net, mark, daddr, spi, proto, family);

	xfrm_hash_ptrs_get(net, &state_ptrs);



	x = __xfrm_state_lookup(&state_ptrs, mark, daddr, spi, proto, family);



	if (x && x->km.state == XFRM_STATE_VALID) {

		spin_lock_bh(&net->xfrm.xfrm_state_lock);
@@ -1155,15 +1191,16 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark, 
}

EXPORT_SYMBOL(xfrm_input_state_lookup);



static struct xfrm_state *__xfrm_state_lookup_byaddr(struct net *net, u32 mark,

static struct xfrm_state *__xfrm_state_lookup_byaddr(const struct xfrm_hash_state_ptrs *state_ptrs,

						     u32 mark,

						     const xfrm_address_t *daddr,

						     const xfrm_address_t *saddr,

						     u8 proto, unsigned short family)

{

	unsigned int h = xfrm_src_hash(net, daddr, saddr, family);

	unsigned int h = __xfrm_src_hash(daddr, saddr, family, state_ptrs->hmask);

	struct xfrm_state *x;



	hlist_for_each_entry_rcu(x, net->xfrm.state_bysrc + h, bysrc) {

	hlist_for_each_entry_rcu(x, state_ptrs->bysrc + h, bysrc) {

		if (x->props.family != family ||

		    x->id.proto     != proto ||

		    !xfrm_addr_equal(&x->id.daddr, daddr, family) ||
@@ -1183,14 +1220,17 @@ static struct xfrm_state *__xfrm_state_lookup_byaddr(struct net *net, u32 mark, 
static inline struct xfrm_state *

__xfrm_state_locate(struct xfrm_state *x, int use_spi, int family)

{

	struct xfrm_hash_state_ptrs state_ptrs;

	struct net *net = xs_net(x);

	u32 mark = x->mark.v & x->mark.m;



	xfrm_hash_ptrs_get(net, &state_ptrs);



	if (use_spi)

		return __xfrm_state_lookup(net, mark, &x->id.daddr,

		return __xfrm_state_lookup(&state_ptrs, mark, &x->id.daddr,

					   x->id.spi, x->id.proto, family);

	else

		return __xfrm_state_lookup_byaddr(net, mark,

		return __xfrm_state_lookup_byaddr(&state_ptrs, mark,

						  &x->id.daddr,

						  &x->props.saddr,

						  x->id.proto, family);
@@ -1264,6 +1304,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, 
		unsigned short family, u32 if_id)

{

	static xfrm_address_t saddr_wildcard = { };

	struct xfrm_hash_state_ptrs state_ptrs;

	struct net *net = xp_net(pol);

	unsigned int h, h_wildcard;

	struct xfrm_state *x, *x0, *to_put;
@@ -1328,8 +1369,10 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, 
	else if (acquire_in_progress) /* XXX: acquire_in_progress should not happen */

		WARN_ON(1);



	h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family);

	hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) {

	xfrm_hash_ptrs_get(net, &state_ptrs);



	h = __xfrm_dst_hash(daddr, saddr, tmpl->reqid, encap_family, state_ptrs.hmask);

	hlist_for_each_entry_rcu(x, state_ptrs.bydst + h, bydst) {

#ifdef CONFIG_XFRM_OFFLOAD

		if (pol->xdo.type == XFRM_DEV_OFFLOAD_PACKET) {

			if (x->xso.type != XFRM_DEV_OFFLOAD_PACKET)
@@ -1362,8 +1405,9 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, 
	if (best || acquire_in_progress)

		goto found;



	h_wildcard = xfrm_dst_hash(net, daddr, &saddr_wildcard, tmpl->reqid, encap_family);

	hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h_wildcard, bydst) {

	h_wildcard = __xfrm_dst_hash(daddr, &saddr_wildcard, tmpl->reqid,

				     encap_family, state_ptrs.hmask);

	hlist_for_each_entry_rcu(x, state_ptrs.bydst + h_wildcard, bydst) {

#ifdef CONFIG_XFRM_OFFLOAD

		if (pol->xdo.type == XFRM_DEV_OFFLOAD_PACKET) {

			if (x->xso.type != XFRM_DEV_OFFLOAD_PACKET)
@@ -1401,7 +1445,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, 


	if (!x && !error && !acquire_in_progress) {

		if (tmpl->id.spi &&

		    (x0 = __xfrm_state_lookup_all(net, mark, daddr,

		    (x0 = __xfrm_state_lookup_all(&state_ptrs, mark, daddr,

						  tmpl->id.spi, tmpl->id.proto,

						  encap_family,

						  &pol->xdo)) != NULL) {
@@ -2180,10 +2224,13 @@ struct xfrm_state * 
xfrm_state_lookup(struct net *net, u32 mark, const xfrm_address_t *daddr, __be32 spi,

		  u8 proto, unsigned short family)

{

	struct xfrm_hash_state_ptrs state_ptrs;

	struct xfrm_state *x;



	rcu_read_lock();

	x = __xfrm_state_lookup(net, mark, daddr, spi, proto, family);

	xfrm_hash_ptrs_get(net, &state_ptrs);



	x = __xfrm_state_lookup(&state_ptrs, mark, daddr, spi, proto, family);

	rcu_read_unlock();

	return x;

}
@@ -2194,10 +2241,14 @@ xfrm_state_lookup_byaddr(struct net *net, u32 mark, 
			 const xfrm_address_t *daddr, const xfrm_address_t *saddr,

			 u8 proto, unsigned short family)

{

	struct xfrm_hash_state_ptrs state_ptrs;

	struct xfrm_state *x;



	spin_lock_bh(&net->xfrm.xfrm_state_lock);

	x = __xfrm_state_lookup_byaddr(net, mark, daddr, saddr, proto, family);



	xfrm_hash_ptrs_get(net, &state_ptrs);



	x = __xfrm_state_lookup_byaddr(&state_ptrs, mark, daddr, saddr, proto, family);

	spin_unlock_bh(&net->xfrm.xfrm_state_lock);

	return x;

}