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Miller" , Jakub Kicinski , Simon Horman , stefan.wiehler@nokia.com, David Ahern Subject: [PATCH v2 net 1/3] ipmr: add debug check for mr table cleanup Date: Sun, 24 Nov 2024 16:40:56 +0100 Message-ID: <64f267b5c0dd74f5bc8795b4ff868b5b103741da.1732289799.git.pabeni@redhat.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Patchwork-Delegate: kuba@kernel.org The multicast route tables lifecycle, for both ipv4 and ipv6, is protected by RCU using the RTNL lock for write access. In many places a table pointer escapes the RCU (or RTNL) protected critical section, but such scenarios are actually safe because tables are deleted only at namespace cleanup time or just after allocation, in case of default rule creation failure. Tables freed at namespace cleanup time are assured to be alive for the whole netns lifetime; tables freed just after creation time are never exposed to other possible users. Ensure that the free conditions are respected in ip{,6}mr_free_table, to document the locking schema and to prevent future possible introduction of 'table del' operation from breaking it. Signed-off-by: Paolo Abeni --- v1 -> v2: - fix build errors with CONFIG_IP{,V6}_MROUTE_MULTIPLE_TABLES=n --- net/ipv4/ipmr.c | 14 ++++++++++++++ net/ipv6/ip6mr.c | 14 ++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index c58dd78509a2..bac0776648e0 100644 --- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -120,6 +120,11 @@ static void ipmr_expire_process(struct timer_list *t); lockdep_rtnl_is_held() || \ list_empty(&net->ipv4.mr_tables)) +static bool ipmr_can_free_table(struct net *net) +{ + return !check_net(net) || !net->ipv4.mr_rules_ops; +} + static struct mr_table *ipmr_mr_table_iter(struct net *net, struct mr_table *mrt) { @@ -302,6 +307,11 @@ EXPORT_SYMBOL(ipmr_rule_default); #define ipmr_for_each_table(mrt, net) \ for (mrt = net->ipv4.mrt; mrt; mrt = NULL) +static bool ipmr_can_free_table(struct net *net) +{ + return !check_net(net); +} + static struct mr_table *ipmr_mr_table_iter(struct net *net, struct mr_table *mrt) { @@ -413,6 +423,10 @@ static struct mr_table *ipmr_new_table(struct net *net, u32 id) static void ipmr_free_table(struct mr_table *mrt) { + struct net *net = read_pnet(&mrt->net); + + DEBUG_NET_WARN_ON_ONCE(!ipmr_can_free_table(net)); + timer_shutdown_sync(&mrt->ipmr_expire_timer); mroute_clean_tables(mrt, MRT_FLUSH_VIFS | MRT_FLUSH_VIFS_STATIC | MRT_FLUSH_MFC | MRT_FLUSH_MFC_STATIC); diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c index d66f58932a79..b80fca894916 100644 --- a/net/ipv6/ip6mr.c +++ b/net/ipv6/ip6mr.c @@ -108,6 +108,11 @@ static void ipmr_expire_process(struct timer_list *t); lockdep_rtnl_is_held() || \ list_empty(&net->ipv6.mr6_tables)) +static bool ip6mr_can_free_table(struct net *net) +{ + return !check_net(net) || !net->ipv6.mr6_rules_ops; +} + static struct mr_table *ip6mr_mr_table_iter(struct net *net, struct mr_table *mrt) { @@ -291,6 +296,11 @@ EXPORT_SYMBOL(ip6mr_rule_default); #define ip6mr_for_each_table(mrt, net) \ for (mrt = net->ipv6.mrt6; mrt; mrt = NULL) +static bool ip6mr_can_free_table(struct net *net) +{ + return !check_net(net); +} + static struct mr_table *ip6mr_mr_table_iter(struct net *net, struct mr_table *mrt) { @@ -392,6 +402,10 @@ static struct mr_table *ip6mr_new_table(struct net *net, u32 id) static void ip6mr_free_table(struct mr_table *mrt) { + struct net *net = read_pnet(&mrt->net); + + DEBUG_NET_WARN_ON_ONCE(!ip6mr_can_free_table(net)); + timer_shutdown_sync(&mrt->ipmr_expire_timer); mroute_clean_tables(mrt, MRT6_FLUSH_MIFS | MRT6_FLUSH_MIFS_STATIC | MRT6_FLUSH_MFC | MRT6_FLUSH_MFC_STATIC);