From 3c10ffddc61f8a1a59e29a110ba70b47e679206a Mon Sep 17 00:00:00 2001 From: Pavel Skripkin Date: Thu, 2 Sep 2021 22:04:00 +0300 Subject: [PATCH 1/5] net: xfrm: fix shift-out-of-bounds in xfrm_get_default Syzbot hit shift-out-of-bounds in xfrm_get_default. The problem was in missing validation check for user data. up->dirmask comes from user-space, so we need to check if this value is less than XFRM_USERPOLICY_DIRMASK_MAX to avoid shift-out-of-bounds bugs. Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") Reported-and-tested-by: syzbot+b2be9dd8ca6f6c73ee2d@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_user.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 03b66d154b2b..4719a6d54aa6 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -2005,6 +2005,11 @@ static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh, return -EMSGSIZE; } + if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX) { + kfree_skb(r_skb); + return -EINVAL; + } + r_up = nlmsg_data(r_nlh); r_up->action = ((net->xfrm.policy_default & (1 << up->dirmask)) >> up->dirmask); From 844f7eaaed9267ae17d33778efe65548cc940205 Mon Sep 17 00:00:00 2001 From: Eugene Syromiatnikov Date: Sun, 12 Sep 2021 14:22:34 +0200 Subject: [PATCH 2/5] include/uapi/linux/xfrm.h: Fix XFRM_MSG_MAPPING ABI breakage Commit 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") broke ABI by changing the value of the XFRM_MSG_MAPPING enum item, thus also evading the build-time check in security/selinux/nlmsgtab.c:selinux_nlmsg_lookup for presence of proper security permission checks in nlmsg_xfrm_perms. Fix it by placing XFRM_MSG_SETDEFAULT/XFRM_MSG_GETDEFAULT to the end of the enum, right before __XFRM_MSG_MAX, and updating the nlmsg_xfrm_perms accordingly. Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") References: https://lore.kernel.org/netdev/20210901151402.GA2557@altlinux.org/ Signed-off-by: Eugene Syromiatnikov Acked-by: Antony Antony Acked-by: Nicolas Dichtel Signed-off-by: Steffen Klassert --- include/uapi/linux/xfrm.h | 6 +++--- security/selinux/nlmsgtab.c | 4 +++- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h index b96c1ea7166d..26f456b1f33e 100644 --- a/include/uapi/linux/xfrm.h +++ b/include/uapi/linux/xfrm.h @@ -213,13 +213,13 @@ enum { XFRM_MSG_GETSPDINFO, #define XFRM_MSG_GETSPDINFO XFRM_MSG_GETSPDINFO + XFRM_MSG_MAPPING, +#define XFRM_MSG_MAPPING XFRM_MSG_MAPPING + XFRM_MSG_SETDEFAULT, #define XFRM_MSG_SETDEFAULT XFRM_MSG_SETDEFAULT XFRM_MSG_GETDEFAULT, #define XFRM_MSG_GETDEFAULT XFRM_MSG_GETDEFAULT - - XFRM_MSG_MAPPING, -#define XFRM_MSG_MAPPING XFRM_MSG_MAPPING __XFRM_MSG_MAX }; #define XFRM_MSG_MAX (__XFRM_MSG_MAX - 1) diff --git a/security/selinux/nlmsgtab.c b/security/selinux/nlmsgtab.c index d59276f48d4f..94ea2a8b2bb7 100644 --- a/security/selinux/nlmsgtab.c +++ b/security/selinux/nlmsgtab.c @@ -126,6 +126,8 @@ static const struct nlmsg_perm nlmsg_xfrm_perms[] = { XFRM_MSG_NEWSPDINFO, NETLINK_XFRM_SOCKET__NLMSG_WRITE }, { XFRM_MSG_GETSPDINFO, NETLINK_XFRM_SOCKET__NLMSG_READ }, { XFRM_MSG_MAPPING, NETLINK_XFRM_SOCKET__NLMSG_READ }, + { XFRM_MSG_SETDEFAULT, NETLINK_XFRM_SOCKET__NLMSG_WRITE }, + { XFRM_MSG_GETDEFAULT, NETLINK_XFRM_SOCKET__NLMSG_READ }, }; static const struct nlmsg_perm nlmsg_audit_perms[] = @@ -189,7 +191,7 @@ int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm) * structures at the top of this file with the new mappings * before updating the BUILD_BUG_ON() macro! */ - BUILD_BUG_ON(XFRM_MSG_MAX != XFRM_MSG_MAPPING); + BUILD_BUG_ON(XFRM_MSG_MAX != XFRM_MSG_GETDEFAULT); err = nlmsg_perm(nlmsg_type, perm, nlmsg_xfrm_perms, sizeof(nlmsg_xfrm_perms)); break; From f8d858e607b2a36808ac6d4218f5f5203d7a7d63 Mon Sep 17 00:00:00 2001 From: Nicolas Dichtel Date: Tue, 14 Sep 2021 16:46:33 +0200 Subject: [PATCH 3/5] xfrm: make user policy API complete >From a userland POV, this API was based on some magic values: - dirmask and action were bitfields but meaning of bits (XFRM_POL_DEFAULT_*) are not exported; - action is confusing, if a bit is set, does it mean drop or accept? Let's try to simplify this uapi by using explicit field and macros. Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") Signed-off-by: Nicolas Dichtel Signed-off-by: Steffen Klassert --- include/uapi/linux/xfrm.h | 9 ++++++--- net/xfrm/xfrm_user.c | 36 +++++++++++++++++++----------------- 2 files changed, 25 insertions(+), 20 deletions(-) diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h index 26f456b1f33e..eda0426ec4c2 100644 --- a/include/uapi/linux/xfrm.h +++ b/include/uapi/linux/xfrm.h @@ -514,9 +514,12 @@ struct xfrm_user_offload { #define XFRM_OFFLOAD_INBOUND 2 struct xfrm_userpolicy_default { -#define XFRM_USERPOLICY_DIRMASK_MAX (sizeof(__u8) * 8) - __u8 dirmask; - __u8 action; +#define XFRM_USERPOLICY_UNSPEC 0 +#define XFRM_USERPOLICY_BLOCK 1 +#define XFRM_USERPOLICY_ACCEPT 2 + __u8 in; + __u8 fwd; + __u8 out; }; #ifndef __KERNEL__ diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 4719a6d54aa6..90c88390f1fe 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1966,16 +1966,21 @@ static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh, { struct net *net = sock_net(skb->sk); struct xfrm_userpolicy_default *up = nlmsg_data(nlh); - u8 dirmask; - u8 old_default = net->xfrm.policy_default; - if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX) - return -EINVAL; + if (up->in == XFRM_USERPOLICY_BLOCK) + net->xfrm.policy_default |= XFRM_POL_DEFAULT_IN; + else if (up->in == XFRM_USERPOLICY_ACCEPT) + net->xfrm.policy_default &= ~XFRM_POL_DEFAULT_IN; - dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK; + if (up->fwd == XFRM_USERPOLICY_BLOCK) + net->xfrm.policy_default |= XFRM_POL_DEFAULT_FWD; + else if (up->fwd == XFRM_USERPOLICY_ACCEPT) + net->xfrm.policy_default &= ~XFRM_POL_DEFAULT_FWD; - net->xfrm.policy_default = (old_default & (0xff ^ dirmask)) - | (up->action << up->dirmask); + if (up->out == XFRM_USERPOLICY_BLOCK) + net->xfrm.policy_default |= XFRM_POL_DEFAULT_OUT; + else if (up->out == XFRM_USERPOLICY_ACCEPT) + net->xfrm.policy_default &= ~XFRM_POL_DEFAULT_OUT; rt_genid_bump_all(net); @@ -1988,13 +1993,11 @@ static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh, struct sk_buff *r_skb; struct nlmsghdr *r_nlh; struct net *net = sock_net(skb->sk); - struct xfrm_userpolicy_default *r_up, *up; + struct xfrm_userpolicy_default *r_up; int len = NLMSG_ALIGN(sizeof(struct xfrm_userpolicy_default)); u32 portid = NETLINK_CB(skb).portid; u32 seq = nlh->nlmsg_seq; - up = nlmsg_data(nlh); - r_skb = nlmsg_new(len, GFP_ATOMIC); if (!r_skb) return -ENOMEM; @@ -2005,15 +2008,14 @@ static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh, return -EMSGSIZE; } - if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX) { - kfree_skb(r_skb); - return -EINVAL; - } - r_up = nlmsg_data(r_nlh); - r_up->action = ((net->xfrm.policy_default & (1 << up->dirmask)) >> up->dirmask); - r_up->dirmask = up->dirmask; + r_up->in = net->xfrm.policy_default & XFRM_POL_DEFAULT_IN ? + XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT; + r_up->fwd = net->xfrm.policy_default & XFRM_POL_DEFAULT_FWD ? + XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT; + r_up->out = net->xfrm.policy_default & XFRM_POL_DEFAULT_OUT ? + XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT; nlmsg_end(r_skb, r_nlh); return nlmsg_unicast(net->xfrm.nlsk, r_skb, portid); From 88d0adb5f13b1c52fbb7d755f6f79db18c2f0c2c Mon Sep 17 00:00:00 2001 From: Nicolas Dichtel Date: Tue, 14 Sep 2021 16:46:34 +0200 Subject: [PATCH 4/5] xfrm: notify default policy on update This configuration knob is very sensible, it should be notified when changing. Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") Signed-off-by: Nicolas Dichtel Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_user.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 90c88390f1fe..0eba0c27c665 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1961,6 +1961,36 @@ static struct sk_buff *xfrm_policy_netlink(struct sk_buff *in_skb, return skb; } +static int xfrm_notify_userpolicy(struct net *net) +{ + struct xfrm_userpolicy_default *up; + int len = NLMSG_ALIGN(sizeof(*up)); + struct nlmsghdr *nlh; + struct sk_buff *skb; + + skb = nlmsg_new(len, GFP_ATOMIC); + if (skb == NULL) + return -ENOMEM; + + nlh = nlmsg_put(skb, 0, 0, XFRM_MSG_GETDEFAULT, sizeof(*up), 0); + if (nlh == NULL) { + kfree_skb(skb); + return -EMSGSIZE; + } + + up = nlmsg_data(nlh); + up->in = net->xfrm.policy_default & XFRM_POL_DEFAULT_IN ? + XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT; + up->fwd = net->xfrm.policy_default & XFRM_POL_DEFAULT_FWD ? + XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT; + up->out = net->xfrm.policy_default & XFRM_POL_DEFAULT_OUT ? + XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT; + + nlmsg_end(skb, nlh); + + return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY); +} + static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh, struct nlattr **attrs) { @@ -1984,6 +2014,7 @@ static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh, rt_genid_bump_all(net); + xfrm_notify_userpolicy(net); return 0; } From 93ec1320b0170d7a207eda2d119c669b673401ed Mon Sep 17 00:00:00 2001 From: Nicolas Dichtel Date: Wed, 22 Sep 2021 10:50:06 +0200 Subject: [PATCH 5/5] xfrm: fix rcu lock in xfrm_notify_userpolicy() As stated in the comment above xfrm_nlmsg_multicast(), rcu read lock must be held before calling this function. Reported-by: syzbot+3d9866419b4aa8f985d6@syzkaller.appspotmail.com Fixes: 703b94b93c19 ("xfrm: notify default policy on update") Signed-off-by: Nicolas Dichtel Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_user.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 0eba0c27c665..3a3cb09eec12 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1967,6 +1967,7 @@ static int xfrm_notify_userpolicy(struct net *net) int len = NLMSG_ALIGN(sizeof(*up)); struct nlmsghdr *nlh; struct sk_buff *skb; + int err; skb = nlmsg_new(len, GFP_ATOMIC); if (skb == NULL) @@ -1988,7 +1989,11 @@ static int xfrm_notify_userpolicy(struct net *net) nlmsg_end(skb, nlh); - return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY); + rcu_read_lock(); + err = xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY); + rcu_read_unlock(); + + return err; } static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh,