From cb79a180f2e7eb51de5a4848652893197637bccb Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 1 Nov 2017 20:30:49 +0100 Subject: xfrm: defer daddr pointer assignment after spi parsing syzbot reports: BUG: KASAN: use-after-free in __xfrm_state_lookup+0x695/0x6b0 Read of size 4 at addr ffff8801d434e538 by task syzkaller647520/2991 [..] __xfrm_state_lookup+0x695/0x6b0 net/xfrm/xfrm_state.c:833 xfrm_state_lookup+0x8a/0x160 net/xfrm/xfrm_state.c:1592 xfrm_input+0x8e5/0x22f0 net/xfrm/xfrm_input.c:302 The use-after-free is the ipv4 destination address, which points to an skb head area that has been reallocated: pskb_expand_head+0x36b/0x1210 net/core/skbuff.c:1494 __pskb_pull_tail+0x14a/0x17c0 net/core/skbuff.c:1877 pskb_may_pull include/linux/skbuff.h:2102 [inline] xfrm_parse_spi+0x3d3/0x4d0 net/xfrm/xfrm_input.c:170 xfrm_input+0xce2/0x22f0 net/xfrm/xfrm_input.c:291 so the real bug is that xfrm_parse_spi() uses pskb_may_pull, but for now do smaller workaround that makes xfrm_input fetch daddr after spi parsing. Reported-by: syzbot Signed-off-by: Florian Westphal Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_input.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c index 8ac9d32fb79d..1c6051cb7733 100644 --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -265,8 +265,6 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) goto lock; } - daddr = (xfrm_address_t *)(skb_network_header(skb) + - XFRM_SPI_SKB_CB(skb)->daddroff); family = XFRM_SPI_SKB_CB(skb)->family; /* if tunnel is present override skb->mark value with tunnel i_key */ @@ -293,6 +291,8 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) goto drop; } + daddr = (xfrm_address_t *)(skb_network_header(skb) + + XFRM_SPI_SKB_CB(skb)->daddroff); do { if (skb->sp->len == XFRM_MAX_DEPTH) { XFRM_INC_STATS(net, LINUX_MIB_XFRMINBUFFERERROR); -- cgit v1.2.3 From cf37966751747727629fe51fd4a1d4edd8457c60 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 2 Nov 2017 16:46:01 +0100 Subject: xfrm: do unconditional template resolution before pcpu cache check Stephen Smalley says: Since 4.14-rc1, the selinux-testsuite has been encountering sporadic failures during testing of labeled IPSEC. git bisect pointed to commit ec30d ("xfrm: add xdst pcpu cache"). The xdst pcpu cache is only checking that the policies are the same, but does not validate that the policy, state, and flow match with respect to security context labeling. As a result, the wrong SA could be used and the receiver could end up performing permission checking and providing SO_PEERSEC or SCM_SECURITY values for the wrong security context. This fix makes it so that we always do the template resolution, and then checks that the found states match those in the pcpu bundle. This has the disadvantage of doing a bit more work (lookup in state hash table) if we can reuse the xdst entry (we only avoid xdst alloc/free) but we don't add a lot of extra work in case we can't reuse. xfrm_pol_dead() check is removed, reasoning is that xfrm_tmpl_resolve does all needed checks. Cc: Paul Moore Fixes: ec30d78c14a813db39a647b6a348b428 ("xfrm: add xdst pcpu cache") Reported-by: Stephen Smalley Tested-by: Stephen Smalley Signed-off-by: Florian Westphal Acked-by: Paul Moore Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_policy.c | 42 ++++++++++++++++++++++++------------------ 1 file changed, 24 insertions(+), 18 deletions(-) (limited to 'net') diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 8cafb3c0a4ac..a2e531bf4f97 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1787,19 +1787,23 @@ void xfrm_policy_cache_flush(void) put_online_cpus(); } -static bool xfrm_pol_dead(struct xfrm_dst *xdst) +static bool xfrm_xdst_can_reuse(struct xfrm_dst *xdst, + struct xfrm_state * const xfrm[], + int num) { - unsigned int num_pols = xdst->num_pols; - unsigned int pol_dead = 0, i; + const struct dst_entry *dst = &xdst->u.dst; + int i; - for (i = 0; i < num_pols; i++) - pol_dead |= xdst->pols[i]->walk.dead; + if (xdst->num_xfrms != num) + return false; - /* Mark DST_OBSOLETE_DEAD to fail the next xfrm_dst_check() */ - if (pol_dead) - xdst->u.dst.obsolete = DST_OBSOLETE_DEAD; + for (i = 0; i < num; i++) { + if (!dst || dst->xfrm != xfrm[i]) + return false; + dst = dst->child; + } - return pol_dead; + return xfrm_bundle_ok(xdst); } static struct xfrm_dst * @@ -1813,26 +1817,28 @@ xfrm_resolve_and_create_bundle(struct xfrm_policy **pols, int num_pols, struct dst_entry *dst; int err; + /* Try to instantiate a bundle */ + err = xfrm_tmpl_resolve(pols, num_pols, fl, xfrm, family); + if (err <= 0) { + if (err != 0 && err != -EAGAIN) + XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTPOLERROR); + return ERR_PTR(err); + } + xdst = this_cpu_read(xfrm_last_dst); if (xdst && xdst->u.dst.dev == dst_orig->dev && xdst->num_pols == num_pols && - !xfrm_pol_dead(xdst) && memcmp(xdst->pols, pols, sizeof(struct xfrm_policy *) * num_pols) == 0 && - xfrm_bundle_ok(xdst)) { + xfrm_xdst_can_reuse(xdst, xfrm, err)) { dst_hold(&xdst->u.dst); + while (err > 0) + xfrm_state_put(xfrm[--err]); return xdst; } old = xdst; - /* Try to instantiate a bundle */ - err = xfrm_tmpl_resolve(pols, num_pols, fl, xfrm, family); - if (err <= 0) { - if (err != 0 && err != -EAGAIN) - XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTPOLERROR); - return ERR_PTR(err); - } dst = xfrm_bundle_create(pols[0], xfrm, err, fl, dst_orig); if (IS_ERR(dst)) { -- cgit v1.2.3 From c9f3f813d462c72dbe412cee6a5cbacf13c4ad5e Mon Sep 17 00:00:00 2001 From: Steffen Klassert Date: Thu, 2 Nov 2017 08:10:17 +0100 Subject: xfrm: Fix stack-out-of-bounds read in xfrm_state_find. When we do tunnel or beet mode, we pass saddr and daddr from the template to xfrm_state_find(), this is ok. On transport mode, we pass the addresses from the flowi, assuming that the IP addresses (and address family) don't change during transformation. This assumption is wrong in the IPv4 mapped IPv6 case, packet is IPv4 and template is IPv6. Fix this by using the addresses from the template unconditionally. Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_policy.c | 29 +++++++++++------------------ 1 file changed, 11 insertions(+), 18 deletions(-) (limited to 'net') diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index a2e531bf4f97..6eb228a70131 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1361,36 +1361,29 @@ xfrm_tmpl_resolve_one(struct xfrm_policy *policy, const struct flowi *fl, struct net *net = xp_net(policy); int nx; int i, error; - xfrm_address_t *daddr = xfrm_flowi_daddr(fl, family); - xfrm_address_t *saddr = xfrm_flowi_saddr(fl, family); xfrm_address_t tmp; for (nx = 0, i = 0; i < policy->xfrm_nr; i++) { struct xfrm_state *x; - xfrm_address_t *remote = daddr; - xfrm_address_t *local = saddr; + xfrm_address_t *local; + xfrm_address_t *remote; struct xfrm_tmpl *tmpl = &policy->xfrm_vec[i]; - if (tmpl->mode == XFRM_MODE_TUNNEL || - tmpl->mode == XFRM_MODE_BEET) { - remote = &tmpl->id.daddr; - local = &tmpl->saddr; - if (xfrm_addr_any(local, tmpl->encap_family)) { - error = xfrm_get_saddr(net, fl->flowi_oif, - &tmp, remote, - tmpl->encap_family, 0); - if (error) - goto fail; - local = &tmp; - } + remote = &tmpl->id.daddr; + local = &tmpl->saddr; + if (xfrm_addr_any(local, tmpl->encap_family)) { + error = xfrm_get_saddr(net, fl->flowi_oif, + &tmp, remote, + tmpl->encap_family, 0); + if (error) + goto fail; + local = &tmp; } x = xfrm_state_find(remote, local, fl, tmpl, policy, &error, family); if (x && x->km.state == XFRM_STATE_VALID) { xfrm[nx++] = x; - daddr = remote; - saddr = local; continue; } if (x) { -- cgit v1.2.3