smc: Fix use-after-free in tcp_write_timer_handler().

JIRA: https://issues.redhat.com/browse/RHEL-73484

commit 9744d2b
Author: Kuniyuki Iwashima <[email protected]>
Date:   Sat Apr 8 11:49:43 2023 -0700

    smc: Fix use-after-free in tcp_write_timer_handler().

    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: ac71387 ("smc: establish new socket family")
    Reported-by: [email protected]
    Link: https://lore.kernel.org/netdev/[email protected]/
    Signed-off-by: Kuniyuki Iwashima <[email protected]>
    Reviewed-by: Tony Lu <[email protected]>
    Signed-off-by: David S. Miller <[email protected]>

Signed-off-by: Mete Durlu <[email protected]>

Author: Mete Durlu

net/smc/af_smc.c

@@ -3278,6 +3278,17 @@ 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;
 	}