[PATCH stable,5.10 0/2] introduce stop timer to solve the problem of CVE-2024-26865

[PATCH stable,5.10 0/2] introduce stop timer to solve the problem of CVE-2024-26865

[Zhengchao Shao]

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(-)

-- 
2.34.1

[PATCH stable,5.10 1/2] tcp: Clean up kernel listener's reqsk in inet_twsk_purge()

[Zhengchao Shao]

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_Ov79Xt8N9FM0XdhCHEN05sf3eLwxKweM6w@mail.gmail.com/

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))
-- 
2.34.1

[PATCH stable,5.10 2/2] tcp: Fix NEW_SYN_RECV handling in inet_twsk_purge()

[Zhengchao Shao]

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/CANn89iLvFuuihCtt9PME2uS1WJATnf5fKjDToa1WzVnRzHnPfg@mail.gmail.com/T/#u
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;
 		}
-- 
2.34.1

Re: [PATCH stable,5.10 0/2] introduce stop timer to solve the problem of CVE-2024-26865

[Greg KH]

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

Re: [PATCH stable,5.10 0/2] introduce stop timer to solve the problem of CVE-2024-26865

[shaozhengchao]

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

Re: [PATCH stable,5.10 0/2] introduce stop timer to solve the problem of CVE-2024-26865

[Greg KH]

On Mon, Apr 29, 2024 at 08:01:44PM +0800, shaozhengchao wrote:
> 
> Hi Greg KH:
>   Thanks for the heads-up. I will work for 5.15.y and 4.19.y.

Thanks for all of the backports, all now queued up.

greg k-h