From: Flavio Leitner <fleitner@redhat.com> Date: Thu, 1 Apr 2010 19:27:41 -0400 Subject: [net] igmp: fix ip_mc_sf_allow race Message-id: <20100401192741.GA2675@redhat.com> Patchwork-id: 23861 O-Subject: [RHEL5.6 PATCH] igmp: fix ip_mc_sf_allow race Bugzilla: 552886 RH-Acked-by: David S. Miller <davem@redhat.com> RH-Acked-by: Thomas Graf <tgraf@redhat.com> RHBZ#: Bug 552886 [RHEL5] ip_mc_sf_allow() has a lock problem https://bugzilla.redhat.com/show_bug.cgi?id=552886 Brew Build: https://brewweb.devel.redhat.com/taskinfo?taskID=2299091 Description: Almost all igmp functions accessing inet->mc_list are protected by rtnl_lock(), but there is one exception which is ip_mc_sf_allow(), so there is a chance of either ip_mc_drop_socket or ip_mc_leave_group remove an entry while ip_mc_sf_allow is running causing a crash. The proposed patch is a backport of upstream commit c85bb41e93184bf5494dde6d8fe5a81b564c84c8 Signed-off-by: Flavio Leitner <fbl@redhat.com> diff --git a/include/linux/igmp.h b/include/linux/igmp.h index 103bfc7..305b787 100644 --- a/include/linux/igmp.h +++ b/include/linux/igmp.h @@ -157,6 +157,7 @@ struct ip_sf_socklist { unsigned int sl_max; unsigned int sl_count; + struct rcu_head rcu; __u32 sl_addr[0]; }; @@ -175,6 +176,7 @@ struct ip_mc_socklist struct ip_mreqn multi; unsigned int sfmode; /* MCAST_{INCLUDE,EXCLUDE} */ struct ip_sf_socklist *sflist; + struct rcu_head rcu; }; struct ip_sf_list diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index d3aa289..15f9b10 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -1780,7 +1780,7 @@ int ip_mc_join_group(struct sock *sk , struct ip_mreqn *imr) iml->next = inet->mc_list; iml->sflist = NULL; iml->sfmode = MCAST_EXCLUDE; - inet->mc_list = iml; + rcu_assign_pointer(inet->mc_list, iml); ip_mc_inc_group(in_dev, addr); err = 0; done: @@ -1788,24 +1788,46 @@ done: return err; } +static void ip_sf_socklist_reclaim(struct rcu_head *rp) +{ + struct ip_sf_socklist *psf; + + psf = container_of(rp, struct ip_sf_socklist, rcu); + /* sk_omem_alloc should have been decreased by the caller*/ + kfree(psf); +} + static int ip_mc_leave_src(struct sock *sk, struct ip_mc_socklist *iml, struct in_device *in_dev) { + struct ip_sf_socklist *psf = iml->sflist; int err; - if (iml->sflist == 0) { + if (psf == NULL) { /* any-source empty exclude case */ return ip_mc_del_src(in_dev, &iml->multi.imr_multiaddr.s_addr, iml->sfmode, 0, NULL, 0); } err = ip_mc_del_src(in_dev, &iml->multi.imr_multiaddr.s_addr, - iml->sfmode, iml->sflist->sl_count, - iml->sflist->sl_addr, 0); - sock_kfree_s(sk, iml->sflist, IP_SFLSIZE(iml->sflist->sl_max)); - iml->sflist = NULL; + iml->sfmode, psf->sl_count, psf->sl_addr, 0); + rcu_assign_pointer(iml->sflist, NULL); + /* decrease mem now to avoid the memleak warning */ + atomic_sub(IP_SFLSIZE(psf->sl_max), &sk->sk_omem_alloc); + call_rcu(&psf->rcu, ip_sf_socklist_reclaim); return err; } + +static void ip_mc_socklist_reclaim(struct rcu_head *rp) +{ + struct ip_mc_socklist *iml; + + iml = container_of(rp, struct ip_mc_socklist, rcu); + /* sk_omem_alloc should have been decreased by the caller*/ + kfree(iml); +} + + /* * Ask a socket to leave a group. */ @@ -1834,12 +1856,14 @@ int ip_mc_leave_group(struct sock *sk, struct ip_mreqn *imr) (void) ip_mc_leave_src(sk, iml, in_dev); - *imlp = iml->next; + rcu_assign_pointer(*imlp, iml->next); if (in_dev) ip_mc_dec_group(in_dev, group); rtnl_unlock(); - sock_kfree_s(sk, iml, sizeof(*iml)); + /* decrease mem now to avoid the memleak warning */ + atomic_sub(sizeof(*iml), &sk->sk_omem_alloc); + call_rcu(&iml->rcu, ip_mc_socklist_reclaim); return 0; } if (!in_dev) @@ -1952,9 +1976,12 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct if (psl) { for (i=0; i<psl->sl_count; i++) newpsl->sl_addr[i] = psl->sl_addr[i]; - sock_kfree_s(sk, psl, IP_SFLSIZE(psl->sl_max)); + /* decrease mem now to avoid the memleak warning */ + atomic_sub(IP_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc); + call_rcu(&psl->rcu, ip_sf_socklist_reclaim); } - pmc->sflist = psl = newpsl; + rcu_assign_pointer(pmc->sflist, newpsl); + psl = newpsl; } rv = 1; /* > 0 for insert logic below if sl_count is 0 */ for (i=0; i<psl->sl_count; i++) { @@ -2049,11 +2076,13 @@ int ip_mc_msfilter(struct sock *sk, struct ip_msfilter *msf, int ifindex) if (psl) { (void) ip_mc_del_src(in_dev, &msf->imsf_multiaddr, pmc->sfmode, psl->sl_count, psl->sl_addr, 0); - sock_kfree_s(sk, psl, IP_SFLSIZE(psl->sl_max)); + /* decrease mem now to avoid the memleak warning */ + atomic_sub(IP_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc); + call_rcu(&psl->rcu, ip_sf_socklist_reclaim); } else (void) ip_mc_del_src(in_dev, &msf->imsf_multiaddr, pmc->sfmode, 0, NULL, 0); - pmc->sflist = newpsl; + rcu_assign_pointer(pmc->sflist, newpsl); pmc->sfmode = msf->imsf_fmode; err = 0; done: @@ -2186,30 +2215,40 @@ int ip_mc_sf_allow(struct sock *sk, u32 loc_addr, u32 rmt_addr, int dif) struct ip_mc_socklist *pmc; struct ip_sf_socklist *psl; int i; + int ret; + ret = 1; if (!MULTICAST(loc_addr)) - return 1; + goto out; - for (pmc=inet->mc_list; pmc; pmc=pmc->next) { + rcu_read_lock(); + for (pmc=rcu_dereference(inet->mc_list); pmc; pmc=rcu_dereference(pmc->next)) { if (pmc->multi.imr_multiaddr.s_addr == loc_addr && pmc->multi.imr_ifindex == dif) break; } + ret = 1; if (!pmc) - return 1; + goto unlock; psl = pmc->sflist; + ret = (pmc->sfmode == MCAST_EXCLUDE); if (!psl) - return pmc->sfmode == MCAST_EXCLUDE; + goto unlock; for (i=0; i<psl->sl_count; i++) { if (psl->sl_addr[i] == rmt_addr) break; } + ret = 0; if (pmc->sfmode == MCAST_INCLUDE && i >= psl->sl_count) - return 0; + goto unlock; if (pmc->sfmode == MCAST_EXCLUDE && i < psl->sl_count) - return 0; - return 1; + goto unlock; + ret = 1; +unlock: + rcu_read_unlock(); +out: + return ret; } /* @@ -2227,7 +2266,7 @@ void ip_mc_drop_socket(struct sock *sk) rtnl_lock(); while ((iml = inet->mc_list) != NULL) { struct in_device *in_dev; - inet->mc_list = iml->next; + rcu_assign_pointer(inet->mc_list, iml->next); in_dev = inetdev_by_index(iml->multi.imr_ifindex); (void) ip_mc_leave_src(sk, iml, in_dev); @@ -2235,7 +2274,9 @@ void ip_mc_drop_socket(struct sock *sk) ip_mc_dec_group(in_dev, iml->multi.imr_multiaddr.s_addr); in_dev_put(in_dev); } - sock_kfree_s(sk, iml, sizeof(*iml)); + /* decrease mem now to avoid the memleak warning */ + atomic_sub(sizeof(*iml), &sk->sk_omem_alloc); + call_rcu(&iml->rcu, ip_mc_socklist_reclaim); } rtnl_unlock(); }