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Date: Wed, 4 Nov 2015 17:04:32 -0200
From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To: Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc: sasha.levin@...cle.com
Subject: Re: [Patch net v2] ipv4: fix a potential deadlock in mcast
getsockopt() path
Em 03-11-2015 21:41, Cong Wang escreveu:
> Sasha reported the following lockdep warning:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(sk_lock-AF_INET);
> lock(rtnl_mutex);
> lock(sk_lock-AF_INET);
> lock(rtnl_mutex);
>
> This is due to that for IP_MSFILTER and MCAST_MSFILTER, we take
> rtnl lock before the socket lock in setsockopt() path, but take
> the socket lock before rtnl lock in getsockopt() path. All the
> rest optnames are setsockopt()-only.
>
> Fix this by aligning the getsockopt() path with the setsockopt()
> path, so that all mcast socket path would be locked in the same
> order.
>
> Note, IPv6 part is different where rtnl lock is not held.
>
> Fixes: 54ff9ef36bdf ("ipv4, ipv6: kill ip_mc_{join, leave}_group and ipv6_sock_mc_{join, drop}")
> Reported-by: Sasha Levin <sasha.levin@...cle.com>
> Cc: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Thanks
> ---
> net/ipv4/igmp.c | 12 ++++--------
> net/ipv4/ip_sockglue.c | 45 ++++++++++++++++++++++++++++++---------------
> 2 files changed, 34 insertions(+), 23 deletions(-)
>
> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index d38b8b6..a2429b7 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -2392,11 +2392,11 @@ int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf,
> struct ip_sf_socklist *psl;
> struct net *net = sock_net(sk);
>
> + ASSERT_RTNL();
> +
> if (!ipv4_is_multicast(addr))
> return -EINVAL;
>
> - rtnl_lock();
> -
> imr.imr_multiaddr.s_addr = msf->imsf_multiaddr;
> imr.imr_address.s_addr = msf->imsf_interface;
> imr.imr_ifindex = 0;
> @@ -2417,7 +2417,6 @@ int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf,
> goto done;
> msf->imsf_fmode = pmc->sfmode;
> psl = rtnl_dereference(pmc->sflist);
> - rtnl_unlock();
> if (!psl) {
> len = 0;
> count = 0;
> @@ -2436,7 +2435,6 @@ int ip_mc_msfget(struct sock *sk, struct ip_msfilter *msf,
> return -EFAULT;
> return 0;
> done:
> - rtnl_unlock();
> return err;
> }
>
> @@ -2450,6 +2448,8 @@ int ip_mc_gsfget(struct sock *sk, struct group_filter *gsf,
> struct inet_sock *inet = inet_sk(sk);
> struct ip_sf_socklist *psl;
>
> + ASSERT_RTNL();
> +
> psin = (struct sockaddr_in *)&gsf->gf_group;
> if (psin->sin_family != AF_INET)
> return -EINVAL;
> @@ -2457,8 +2457,6 @@ int ip_mc_gsfget(struct sock *sk, struct group_filter *gsf,
> if (!ipv4_is_multicast(addr))
> return -EINVAL;
>
> - rtnl_lock();
> -
> err = -EADDRNOTAVAIL;
>
> for_each_pmc_rtnl(inet, pmc) {
> @@ -2470,7 +2468,6 @@ int ip_mc_gsfget(struct sock *sk, struct group_filter *gsf,
> goto done;
> gsf->gf_fmode = pmc->sfmode;
> psl = rtnl_dereference(pmc->sflist);
> - rtnl_unlock();
> count = psl ? psl->sl_count : 0;
> copycount = count < gsf->gf_numsrc ? count : gsf->gf_numsrc;
> gsf->gf_numsrc = count;
> @@ -2490,7 +2487,6 @@ int ip_mc_gsfget(struct sock *sk, struct group_filter *gsf,
> }
> return 0;
> done:
> - rtnl_unlock();
> return err;
> }
>
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index c3c359a..5f73a7c 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -1251,11 +1251,22 @@ EXPORT_SYMBOL(compat_ip_setsockopt);
> * the _received_ ones. The set sets the _sent_ ones.
> */
>
> +static bool getsockopt_needs_rtnl(int optname)
> +{
> + switch (optname) {
> + case IP_MSFILTER:
> + case MCAST_MSFILTER:
> + return true;
> + }
> + return false;
> +}
> +
> static int do_ip_getsockopt(struct sock *sk, int level, int optname,
> char __user *optval, int __user *optlen, unsigned int flags)
> {
> struct inet_sock *inet = inet_sk(sk);
> - int val;
> + bool needs_rtnl = getsockopt_needs_rtnl(optname);
> + int val, err = 0;
> int len;
>
> if (level != SOL_IP)
> @@ -1269,6 +1280,8 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
> if (len < 0)
> return -EINVAL;
>
> + if (needs_rtnl)
> + rtnl_lock();
> lock_sock(sk);
>
> switch (optname) {
> @@ -1386,39 +1399,35 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
> case IP_MSFILTER:
> {
> struct ip_msfilter msf;
> - int err;
>
> if (len < IP_MSFILTER_SIZE(0)) {
> - release_sock(sk);
> - return -EINVAL;
> + err = -EINVAL;
> + goto out;
> }
> if (copy_from_user(&msf, optval, IP_MSFILTER_SIZE(0))) {
> - release_sock(sk);
> - return -EFAULT;
> + err = -EFAULT;
> + goto out;
> }
> err = ip_mc_msfget(sk, &msf,
> (struct ip_msfilter __user *)optval, optlen);
> - release_sock(sk);
> - return err;
> + goto out;
> }
> case MCAST_MSFILTER:
> {
> struct group_filter gsf;
> - int err;
>
> if (len < GROUP_FILTER_SIZE(0)) {
> - release_sock(sk);
> - return -EINVAL;
> + err = -EINVAL;
> + goto out;
> }
> if (copy_from_user(&gsf, optval, GROUP_FILTER_SIZE(0))) {
> - release_sock(sk);
> - return -EFAULT;
> + err = -EFAULT;
> + goto out;
> }
> err = ip_mc_gsfget(sk, &gsf,
> (struct group_filter __user *)optval,
> optlen);
> - release_sock(sk);
> - return err;
> + goto out;
> }
> case IP_MULTICAST_ALL:
> val = inet->mc_all;
> @@ -1485,6 +1494,12 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
> return -EFAULT;
> }
> return 0;
> +
> +out:
> + release_sock(sk);
> + if (needs_rtnl)
> + rtnl_unlock();
> + return err;
> }
>
> int ip_getsockopt(struct sock *sk, int level,
>
--
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