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Message-ID: <825f4a1c-9cc0-4ab4-8b80-3b704e55b681@schaufler-ca.com>
Date: Fri, 10 May 2024 10:37:01 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Davide Caratti <dcaratti@...hat.com>, Paul Moore <paul@...l-moore.com>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>
Cc: linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
Xiumei Mu <xmu@...hat.com>, Ondrej Mosnacek <omosnace@...hat.com>,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH net v5] netlabel: fix RCU annotation for IPv4 options on
socket creation
On 5/10/2024 10:19 AM, Davide Caratti wrote:
> Xiumei reports the following splat when netlabel and TCP socket are used:
>
> =============================
> WARNING: suspicious RCU usage
> 6.9.0-rc2+ #637 Not tainted
> -----------------------------
> net/ipv4/cipso_ipv4.c:1880 suspicious rcu_dereference_protected() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by ncat/23333:
> #0: ffffffff906030c0 (rcu_read_lock){....}-{1:2}, at: netlbl_sock_setattr+0x25/0x1b0
>
> stack backtrace:
> CPU: 11 PID: 23333 Comm: ncat Kdump: loaded Not tainted 6.9.0-rc2+ #637
> Hardware name: Supermicro SYS-6027R-72RF/X9DRH-7TF/7F/iTF/iF, BIOS 3.0 07/26/2013
> Call Trace:
> <TASK>
> dump_stack_lvl+0xa9/0xc0
> lockdep_rcu_suspicious+0x117/0x190
> cipso_v4_sock_setattr+0x1ab/0x1b0
> netlbl_sock_setattr+0x13e/0x1b0
> selinux_netlbl_socket_post_create+0x3f/0x80
> selinux_socket_post_create+0x1a0/0x460
> security_socket_post_create+0x42/0x60
> __sock_create+0x342/0x3a0
> __sys_socket_create.part.22+0x42/0x70
> __sys_socket+0x37/0xb0
> __x64_sys_socket+0x16/0x20
> do_syscall_64+0x96/0x180
> ? do_user_addr_fault+0x68d/0xa30
> ? exc_page_fault+0x171/0x280
> ? asm_exc_page_fault+0x22/0x30
> entry_SYSCALL_64_after_hwframe+0x71/0x79
> RIP: 0033:0x7fbc0ca3fc1b
> Code: 73 01 c3 48 8b 0d 05 f2 1b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 29 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d d5 f1 1b 00 f7 d8 64 89 01 48
> RSP: 002b:00007fff18635208 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
> RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fbc0ca3fc1b
> RDX: 0000000000000006 RSI: 0000000000000001 RDI: 0000000000000002
> RBP: 000055d24f80f8a0 R08: 0000000000000003 R09: 0000000000000001
>
> R10: 0000000000020000 R11: 0000000000000246 R12: 000055d24f80f8a0
> R13: 0000000000000000 R14: 000055d24f80fb88 R15: 0000000000000000
> </TASK>
>
> The current implementation of cipso_v4_sock_setattr() replaces IP options
> under the assumption that the caller holds the socket lock; however, such
> assumption is not true, nor needed, in selinux_socket_post_create() hook.
>
> Let all callers of cipso_v4_sock_setattr() specify the "socket lock held"
> condition, except selinux_socket_post_create() _ where such condition can
> safely be set as true even without holding the socket lock.
>
> v5:
> - fix kernel-doc
> - adjust #idfefs around prototype of netlbl_sk_lock_check() (thanks Paul Moore)
>
> v4:
> - fix build when CONFIG_LOCKDEP is unset (thanks kernel test robot)
>
> v3:
> - rename variable to 'sk_locked' (thanks Paul Moore)
> - keep rcu_replace_pointer() open-coded and re-add NULL check of 'old',
> these two changes will be posted in another patch (thanks Paul Moore)
>
> v2:
> - pass lockdep_sock_is_held() through a boolean variable in the stack
> (thanks Eric Dumazet, Paul Moore, Casey Schaufler)
> - use rcu_replace_pointer() instead of rcu_dereference_protected() +
> rcu_assign_pointer()
> - remove NULL check of 'old' before kfree_rcu()
>
> Fixes: f6d8bd051c39 ("inet: add RCU protection to inet->opt")
> Reported-by: Xiumei Mu <xmu@...hat.com>
> Acked-by: Paul Moore <paul@...l-moore.com>
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>
Acked-by: Casey Schaufler <casey@...aufler-ca.com>
> ---
> include/net/cipso_ipv4.h | 6 ++++--
> include/net/netlabel.h | 12 ++++++++++--
> net/ipv4/cipso_ipv4.c | 7 ++++---
> net/netlabel/netlabel_kapi.c | 31 ++++++++++++++++++++++++++++---
> security/selinux/netlabel.c | 5 ++++-
> security/smack/smack_lsm.c | 3 ++-
> 6 files changed, 52 insertions(+), 12 deletions(-)
>
> diff --git a/include/net/cipso_ipv4.h b/include/net/cipso_ipv4.h
> index 53dd7d988a2d..c9111bb2f59b 100644
> --- a/include/net/cipso_ipv4.h
> +++ b/include/net/cipso_ipv4.h
> @@ -183,7 +183,8 @@ int cipso_v4_getattr(const unsigned char *cipso,
> struct netlbl_lsm_secattr *secattr);
> int cipso_v4_sock_setattr(struct sock *sk,
> const struct cipso_v4_doi *doi_def,
> - const struct netlbl_lsm_secattr *secattr);
> + const struct netlbl_lsm_secattr *secattr,
> + bool sk_locked);
> void cipso_v4_sock_delattr(struct sock *sk);
> int cipso_v4_sock_getattr(struct sock *sk, struct netlbl_lsm_secattr *secattr);
> int cipso_v4_req_setattr(struct request_sock *req,
> @@ -214,7 +215,8 @@ static inline int cipso_v4_getattr(const unsigned char *cipso,
>
> static inline int cipso_v4_sock_setattr(struct sock *sk,
> const struct cipso_v4_doi *doi_def,
> - const struct netlbl_lsm_secattr *secattr)
> + const struct netlbl_lsm_secattr *secattr,
> + bool sk_locked)
> {
> return -ENOSYS;
> }
> diff --git a/include/net/netlabel.h b/include/net/netlabel.h
> index f3ab0b8a4b18..2133ad723fc1 100644
> --- a/include/net/netlabel.h
> +++ b/include/net/netlabel.h
> @@ -470,7 +470,8 @@ void netlbl_bitmap_setbit(unsigned char *bitmap, u32 bit, u8 state);
> int netlbl_enabled(void);
> int netlbl_sock_setattr(struct sock *sk,
> u16 family,
> - const struct netlbl_lsm_secattr *secattr);
> + const struct netlbl_lsm_secattr *secattr,
> + bool sk_locked);
> void netlbl_sock_delattr(struct sock *sk);
> int netlbl_sock_getattr(struct sock *sk,
> struct netlbl_lsm_secattr *secattr);
> @@ -487,6 +488,7 @@ int netlbl_skbuff_getattr(const struct sk_buff *skb,
> u16 family,
> struct netlbl_lsm_secattr *secattr);
> void netlbl_skbuff_err(struct sk_buff *skb, u16 family, int error, int gateway);
> +bool netlbl_sk_lock_check(struct sock *sk);
>
> /*
> * LSM label mapping cache operations
> @@ -614,7 +616,8 @@ static inline int netlbl_enabled(void)
> }
> static inline int netlbl_sock_setattr(struct sock *sk,
> u16 family,
> - const struct netlbl_lsm_secattr *secattr)
> + const struct netlbl_lsm_secattr *secattr,
> + bool sk_locked)
> {
> return -ENOSYS;
> }
> @@ -673,6 +676,11 @@ static inline struct audit_buffer *netlbl_audit_start(int type,
> {
> return NULL;
> }
> +
> +static inline bool netlbl_sk_lock_check(struct sock *sk)
> +{
> + return true;
> +}
> #endif /* CONFIG_NETLABEL */
>
> const struct netlbl_calipso_ops *
> diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
> index 8b17d83e5fde..dd6d46015058 100644
> --- a/net/ipv4/cipso_ipv4.c
> +++ b/net/ipv4/cipso_ipv4.c
> @@ -1815,6 +1815,7 @@ static int cipso_v4_genopt(unsigned char *buf, u32 buf_len,
> * @sk: the socket
> * @doi_def: the CIPSO DOI to use
> * @secattr: the specific security attributes of the socket
> + * @sk_locked: true if caller holds the socket lock
> *
> * Description:
> * Set the CIPSO option on the given socket using the DOI definition and
> @@ -1826,7 +1827,8 @@ static int cipso_v4_genopt(unsigned char *buf, u32 buf_len,
> */
> int cipso_v4_sock_setattr(struct sock *sk,
> const struct cipso_v4_doi *doi_def,
> - const struct netlbl_lsm_secattr *secattr)
> + const struct netlbl_lsm_secattr *secattr,
> + bool sk_locked)
> {
> int ret_val = -EPERM;
> unsigned char *buf = NULL;
> @@ -1876,8 +1878,7 @@ int cipso_v4_sock_setattr(struct sock *sk,
>
> sk_inet = inet_sk(sk);
>
> - old = rcu_dereference_protected(sk_inet->inet_opt,
> - lockdep_sock_is_held(sk));
> + old = rcu_dereference_protected(sk_inet->inet_opt, sk_locked);
> if (inet_test_bit(IS_ICSK, sk)) {
> sk_conn = inet_csk(sk);
> if (old)
> diff --git a/net/netlabel/netlabel_kapi.c b/net/netlabel/netlabel_kapi.c
> index 1ba4f58e1d35..cd9160bbc919 100644
> --- a/net/netlabel/netlabel_kapi.c
> +++ b/net/netlabel/netlabel_kapi.c
> @@ -965,6 +965,7 @@ int netlbl_enabled(void)
> * @sk: the socket to label
> * @family: protocol family
> * @secattr: the security attributes
> + * @sk_locked: true if caller holds the socket lock
> *
> * Description:
> * Attach the correct label to the given socket using the security attributes
> @@ -977,7 +978,8 @@ int netlbl_enabled(void)
> */
> int netlbl_sock_setattr(struct sock *sk,
> u16 family,
> - const struct netlbl_lsm_secattr *secattr)
> + const struct netlbl_lsm_secattr *secattr,
> + bool sk_locked)
> {
> int ret_val;
> struct netlbl_dom_map *dom_entry;
> @@ -997,7 +999,7 @@ int netlbl_sock_setattr(struct sock *sk,
> case NETLBL_NLTYPE_CIPSOV4:
> ret_val = cipso_v4_sock_setattr(sk,
> dom_entry->def.cipso,
> - secattr);
> + secattr, sk_locked);
> break;
> case NETLBL_NLTYPE_UNLABELED:
> ret_val = 0;
> @@ -1090,6 +1092,28 @@ int netlbl_sock_getattr(struct sock *sk,
> return ret_val;
> }
>
> +/**
> + * netlbl_sk_lock_check - Check if the socket lock has been acquired.
> + * @sk: the socket to be checked
> + *
> + * Return: true if socket @sk is locked or if lock debugging is disabled at
> + * runtime or compile-time; false otherwise
> + *
> + */
> +#ifdef CONFIG_LOCKDEP
> +bool netlbl_sk_lock_check(struct sock *sk)
> +{
> + if (debug_locks)
> + return lockdep_sock_is_held(sk);
> + return true;
> +}
> +#else
> +bool netlbl_sk_lock_check(struct sock *sk)
> +{
> + return true;
> +}
> +#endif
> +
> /**
> * netlbl_conn_setattr - Label a connected socket using the correct protocol
> * @sk: the socket to label
> @@ -1126,7 +1150,8 @@ int netlbl_conn_setattr(struct sock *sk,
> switch (entry->type) {
> case NETLBL_NLTYPE_CIPSOV4:
> ret_val = cipso_v4_sock_setattr(sk,
> - entry->cipso, secattr);
> + entry->cipso, secattr,
> + netlbl_sk_lock_check(sk));
> break;
> case NETLBL_NLTYPE_UNLABELED:
> /* just delete the protocols we support for right now
> diff --git a/security/selinux/netlabel.c b/security/selinux/netlabel.c
> index 8f182800e412..55885634e880 100644
> --- a/security/selinux/netlabel.c
> +++ b/security/selinux/netlabel.c
> @@ -402,7 +402,10 @@ int selinux_netlbl_socket_post_create(struct sock *sk, u16 family)
> secattr = selinux_netlbl_sock_genattr(sk);
> if (secattr == NULL)
> return -ENOMEM;
> - rc = netlbl_sock_setattr(sk, family, secattr);
> + /* On socket creation, replacement of IP options is safe even if
> + * the caller does not hold the socket lock.
> + */
> + rc = netlbl_sock_setattr(sk, family, secattr, true);
> switch (rc) {
> case 0:
> sksec->nlbl_state = NLBL_LABELED;
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 146667937811..efeac8365ad0 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -2565,7 +2565,8 @@ static int smack_netlbl_add(struct sock *sk)
> local_bh_disable();
> bh_lock_sock_nested(sk);
>
> - rc = netlbl_sock_setattr(sk, sk->sk_family, &skp->smk_netlabel);
> + rc = netlbl_sock_setattr(sk, sk->sk_family, &skp->smk_netlabel,
> + netlbl_sk_lock_check(sk));
> switch (rc) {
> case 0:
> ssp->smk_state = SMK_NETLBL_LABELED;
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