This is a note to let you know that I've just added the patch titled
smc: Fix use-after-free in tcp_write_timer_handler().
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
smc-fix-use-after-free-in-tcp_write_timer_handler.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5b96877a142c2eb06a4ef317ad0a949862922575
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date: Sat Apr 8 11:49:43 2023 -0700
smc: Fix use-after-free in tcp_write_timer_handler().
[ Upstream commit 9744d2bf19762703704ecba885b7ac282c02eacf ]
With Eric's ref tracker, syzbot finally found a repro for
use-after-free in tcp_write_timer_handler() by kernel TCP
sockets. [0]
If SMC creates a kernel socket in __smc_create(), the kernel
socket is supposed to be freed in smc_clcsock_release() by
calling sock_release() when we close() the parent SMC socket.
However, at the end of smc_clcsock_release(), the kernel
socket's sk_state might not be TCP_CLOSE. This means that
we have not called inet_csk_destroy_sock() in __tcp_close()
and have not stopped the TCP timers.
The kernel socket's TCP timers can be fired later, so we
need to hold a refcnt for net as we do for MPTCP subflows
in mptcp_subflow_create_socket().
[0]:
leaked reference.
sk_alloc (./include/net/net_namespace.h:335 net/core/sock.c:2108)
inet_create (net/ipv4/af_inet.c:319 net/ipv4/af_inet.c:244)
__sock_create (net/socket.c:1546)
smc_create (net/smc/af_smc.c:3269 net/smc/af_smc.c:3284)
__sock_create (net/socket.c:1546)
__sys_socket (net/socket.c:1634 net/socket.c:1618 net/socket.c:1661)
__x64_sys_socket (net/socket.c:1672)
do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
==================================================================
BUG: KASAN: slab-use-after-free in tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594)
Read of size 1 at addr ffff888052b65e0d by task syzrepro/18091
CPU: 0 PID: 18091 Comm: syzrepro Tainted: G W 6.3.0-rc4-01174-gb5d54eb5899a #7
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl (lib/dump_stack.c:107)
print_report (mm/kasan/report.c:320 mm/kasan/report.c:430)
kasan_report (mm/kasan/report.c:538)
tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594)
tcp_write_timer (./include/linux/spinlock.h:390 net/ipv4/tcp_timer.c:643)
call_timer_fn (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701)
__run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2022)
run_timer_softirq (kernel/time/timer.c:2037)
__do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:572)
__irq_exit_rcu (kernel/softirq.c:445 kernel/softirq.c:650)
irq_exit_rcu (kernel/softirq.c:664)
sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1107 (discriminator 14))
</IRQ>
Fixes: ac7138746e14 ("smc: establish new socket family")
Reported-by: syzbot+7e1e1bdb852961150198@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/netdev/000000000000a3f51805f8bcc43a@xxxxxxxxxx/
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Reviewed-by: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index e8018b0fb7676..bdeaee727538d 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -3257,6 +3257,17 @@ static int __smc_create(struct net *net, struct socket *sock, int protocol,
sk_common_release(sk);
goto out;
}
+
+ /* smc_clcsock_release() does not wait smc->clcsock->sk's
+ * destruction; its sk_state might not be TCP_CLOSE after
+ * smc->sk is close()d, and TCP timers can be fired later,
+ * which need net ref.
+ */
+ sk = smc->clcsock->sk;
+ __netns_tracker_free(net, &sk->ns_tracker, false);
+ sk->sk_net_refcnt = 1;
+ get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
+ sock_inuse_add(net, 1);
} else {
smc->clcsock = clcsock;
}
