For the CVE-2024-26865 issue, the stable 5.10 branch code also involves this issue. However, the patch of the mainline version cannot be used on stable 5.10 branch. The commit 740ea3c4a0b2("tcp: Clean up kernel listener' s reqsk in inet_twsk_purge()") is required to stop the timer.
Eric Dumazet (1): tcp: Fix NEW_SYN_RECV handling in inet_twsk_purge()
Kuniyuki Iwashima (1): tcp: Clean up kernel listener's reqsk in inet_twsk_purge()
net/ipv4/inet_timewait_sock.c | 32 +++++++++++++++++++++----------- 1 file changed, 21 insertions(+), 11 deletions(-)
From: Kuniyuki Iwashima kuniyu@amazon.com
commit 740ea3c4a0b2e326b23d7cdf05472a0e92aa39bc upstream
Eric Dumazet reported a use-after-free related to the per-netns ehash series. [0]
When we create a TCP socket from userspace, the socket always holds a refcnt of the netns. This guarantees that a reqsk timer is always fired before netns dismantle. Each reqsk has a refcnt of its listener, so the listener is not freed before the reqsk, and the net is not freed before the listener as well.
OTOH, when in-kernel users create a TCP socket, it might not hold a refcnt of its netns. Thus, a reqsk timer can be fired after the netns dismantle and access freed per-netns ehash.
To avoid the use-after-free, we need to clean up TCP_NEW_SYN_RECV sockets in inet_twsk_purge() if the netns uses a per-netns ehash.
[0]: https://lore.kernel.org/netdev/CANn89iLXMup0dRD_Ov79Xt8N9FM0XdhCHEN05sf3eLwx...
BUG: KASAN: use-after-free in tcp_or_dccp_get_hashinfo include/net/inet_hashtables.h:181 [inline] BUG: KASAN: use-after-free in reqsk_queue_unlink+0x320/0x350 net/ipv4/inet_connection_sock.c:913 Read of size 8 at addr ffff88807545bd80 by task syz-executor.2/8301
CPU: 1 PID: 8301 Comm: syz-executor.2 Not tainted 6.0.0-syzkaller-02757-gaf7d23f9d96a #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:317 [inline] print_report.cold+0x2ba/0x719 mm/kasan/report.c:433 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495 tcp_or_dccp_get_hashinfo include/net/inet_hashtables.h:181 [inline] reqsk_queue_unlink+0x320/0x350 net/ipv4/inet_connection_sock.c:913 inet_csk_reqsk_queue_drop net/ipv4/inet_connection_sock.c:927 [inline] inet_csk_reqsk_queue_drop_and_put net/ipv4/inet_connection_sock.c:939 [inline] reqsk_timer_handler+0x724/0x1160 net/ipv4/inet_connection_sock.c:1053 call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474 expire_timers kernel/time/timer.c:1519 [inline] __run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790 __run_timers kernel/time/timer.c:1768 [inline] run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803 __do_softirq+0x1d0/0x9c8 kernel/softirq.c:571 invoke_softirq kernel/softirq.c:445 [inline] __irq_exit_rcu+0x123/0x180 kernel/softirq.c:650 irq_exit_rcu+0x5/0x20 kernel/softirq.c:662 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1107 </IRQ>
Fixes: d1e5e6408b30 ("tcp: Introduce optional per-netns ehash.") Reported-by: syzbot syzkaller@googlegroups.com Reported-by: Eric Dumazet edumazet@google.com Suggested-by: Eric Dumazet edumazet@google.com Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/20221012145036.74960-1-kuniyu@amazon.com Signed-off-by: Jakub Kicinski kuba@kernel.org [shaozhengchao: resolved conflicts in 5.10] Signed-off-by: Zhengchao Shao shaozhengchao@huawei.com --- net/ipv4/inet_timewait_sock.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index c411c87ae865..04726bbd72dc 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -268,8 +268,21 @@ void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) rcu_read_lock(); restart: sk_nulls_for_each_rcu(sk, node, &head->chain) { - if (sk->sk_state != TCP_TIME_WAIT) + if (sk->sk_state != TCP_TIME_WAIT) { + /* A kernel listener socket might not hold refcnt for net, + * so reqsk_timer_handler() could be fired after net is + * freed. Userspace listener and reqsk never exist here. + */ + if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV && + hashinfo->pernet)) { + struct request_sock *req = inet_reqsk(sk); + + inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req); + } + continue; + } + tw = inet_twsk(sk); if ((tw->tw_family != family) || refcount_read(&twsk_net(tw)->count))
From: Eric Dumazet edumazet@google.com
commit 1c4e97dd2d3c9a3e84f7e26346aa39bc426d3249 upstream
inet_twsk_purge() uses rcu to find TIME_WAIT and NEW_SYN_RECV objects to purge.
These objects use SLAB_TYPESAFE_BY_RCU semantic and need special care. We need to use refcount_inc_not_zero(&sk->sk_refcnt).
Reuse the existing correct logic I wrote for TIME_WAIT, because both structures have common locations for sk_state, sk_family, and netns pointer.
If after the refcount_inc_not_zero() the object fields longer match the keys, use sock_gen_put(sk) to release the refcount.
Then we can call inet_twsk_deschedule_put() for TIME_WAIT, inet_csk_reqsk_queue_drop_and_put() for NEW_SYN_RECV sockets, with BH disabled.
Then we need to restart the loop because we had drop rcu_read_lock().
Fixes: 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in inet_twsk_purge()") Link: https://lore.kernel.org/netdev/CANn89iLvFuuihCtt9PME2uS1WJATnf5fKjDToa1WzVnR... Signed-off-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/20240308200122.64357-2-kuniyu@amazon.com Signed-off-by: Jakub Kicinski kuba@kernel.org [shaozhengchao: resolved conflicts in 5.10] Signed-off-by: Zhengchao Shao shaozhengchao@huawei.com --- net/ipv4/inet_timewait_sock.c | 41 ++++++++++++++++------------------- 1 file changed, 19 insertions(+), 22 deletions(-)
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index 04726bbd72dc..85cb44bfa3ba 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -254,12 +254,12 @@ void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) } EXPORT_SYMBOL_GPL(__inet_twsk_schedule);
+/* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */ void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) { - struct inet_timewait_sock *tw; - struct sock *sk; struct hlist_nulls_node *node; unsigned int slot; + struct sock *sk;
for (slot = 0; slot <= hashinfo->ehash_mask; slot++) { struct inet_ehash_bucket *head = &hashinfo->ehash[slot]; @@ -268,38 +268,35 @@ void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) rcu_read_lock(); restart: sk_nulls_for_each_rcu(sk, node, &head->chain) { - if (sk->sk_state != TCP_TIME_WAIT) { - /* A kernel listener socket might not hold refcnt for net, - * so reqsk_timer_handler() could be fired after net is - * freed. Userspace listener and reqsk never exist here. - */ - if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV && - hashinfo->pernet)) { - struct request_sock *req = inet_reqsk(sk); - - inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req); - } + int state = inet_sk_state_load(sk);
+ if ((1 << state) & ~(TCPF_TIME_WAIT | + TCPF_NEW_SYN_RECV)) continue; - }
- tw = inet_twsk(sk); - if ((tw->tw_family != family) || - refcount_read(&twsk_net(tw)->count)) + if (sk->sk_family != family || + refcount_read(&sock_net(sk)->count)) continue;
- if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt))) + if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) continue;
- if (unlikely((tw->tw_family != family) || - refcount_read(&twsk_net(tw)->count))) { - inet_twsk_put(tw); + if (unlikely(sk->sk_family != family || + refcount_read(&sock_net(sk)->count))) { + sock_gen_put(sk); goto restart; }
rcu_read_unlock(); local_bh_disable(); - inet_twsk_deschedule_put(tw); + if (state == TCP_TIME_WAIT) { + inet_twsk_deschedule_put(inet_twsk(sk)); + } else { + struct request_sock *req = inet_reqsk(sk); + + inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, + req); + } local_bh_enable(); goto restart_rcu; }
On Sun, Apr 28, 2024 at 11:49:46AM +0800, Zhengchao Shao wrote:
For the CVE-2024-26865 issue, the stable 5.10 branch code also involves this issue. However, the patch of the mainline version cannot be used on stable 5.10 branch. The commit 740ea3c4a0b2("tcp: Clean up kernel listener' s reqsk in inet_twsk_purge()") is required to stop the timer.
This is also needed for 5.15.y, so we can not take a 5.10.y only patch, you know this :(
Please also provide a working set of 5.15.y patches and then I'll be glad to queue these 5.10.y ones up.
thanks,
greg k-h
Hi Greg KH: Thanks for the heads-up. I will work for 5.15.y and 4.19.y.
Thank you.
Zhengchao Shao
On 2024/4/29 19:11, Greg KH wrote:
On Sun, Apr 28, 2024 at 11:49:46AM +0800, Zhengchao Shao wrote:
For the CVE-2024-26865 issue, the stable 5.10 branch code also involves this issue. However, the patch of the mainline version cannot be used on stable 5.10 branch. The commit 740ea3c4a0b2("tcp: Clean up kernel listener' s reqsk in inet_twsk_purge()") is required to stop the timer.
This is also needed for 5.15.y, so we can not take a 5.10.y only patch, you know this :(
Please also provide a working set of 5.15.y patches and then I'll be glad to queue these 5.10.y ones up.
thanks,
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
shaozhengchao -
Zhengchao Shao