use-after-free in inet6_destroy_sock

[Dmitry Vyukov <dvyukov@google.com>]

Hello,

The following program causes use-after-free in inet6_destroy_sock:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <syscall.h>
#include <string.h>
#include <stdint.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <linux/in.h>
#include <linux/in6.h>

int cfd = -1;

void *thr(void *arg)
{
        cfd = syscall(SYS_socket, PF_INET6, SOCK_STREAM, IPPROTO_SCTP);
        struct sockaddr_in6 sa = {};
        sa.sin6_family = AF_INET6;
        sa.sin6_port = getpid();
        sa.sin6_addr.s6_addr[15] = 1;
        syscall(SYS_connect, cfd, &sa, sizeof(sa), 0, 0, 0);
        return 0;
}

int main()
{
        syscall(SYS_mmap, 0x20000000ul, 0x10000ul, 0x3ul, 0x32ul,
0xfffffffffffffffful, 0x0ul);
        int fd = syscall(SYS_socket, PF_INET6, SOCK_STREAM, IPPROTO_SCTP);
        struct sockaddr_in6 sa = {};
        sa.sin6_family = AF_INET6;
        sa.sin6_port = getpid();
        sa.sin6_addr.s6_addr[15] = 1;
        syscall(SYS_bind, fd, &sa, sizeof(sa), 0, 0, 0);
        syscall(SYS_listen, fd, 0x3ul, 0, 0, 0, 0);
        memcpy((void*)0x20002ff6,
"\x10\x48\xe0\xad\x68\xc0\xce\x4c\xd0\xb5", 10);
        syscall(SYS_setsockopt, fd, 0x29ul, 0x6ul, 0x20002ff6ul, 0xaul, 0);
        pthread_t th;
        pthread_create(&th, 0, thr, 0);
        pthread_join(th, 0);
        int sfd = syscall(SYS_accept4, fd, 0x20003f80ul, 0x20003ab4ul,
0x80800ul, 0, 0);
        dup3(fd, -1, 0x80000);
        return 0;
}


==================================================================
BUG: KASAN: use-after-free in inet6_destroy_sock+0x177/0x1c0 at addr
ffff8800349179b4
Read of size 4 by task executor/7001
=============================================================================
BUG kmalloc-96 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------

Disabling lock debugging due to kernel taint
INFO: Allocated in sock_kmalloc+0x93/0x100 age=20 cpu=0 pid=7064
[<      none      >] ___slab_alloc+0x648/0x8c0 mm/slub.c:2468
[<      none      >] __slab_alloc+0x4c/0x90 mm/slub.c:2497
[<     inline     >] slab_alloc_node mm/slub.c:2560
[<     inline     >] slab_alloc mm/slub.c:2602
[<      none      >] __kmalloc+0x2d9/0x480 mm/slub.c:3562
[<     inline     >] kmalloc include/linux/slab.h:463
[<      none      >] sock_kmalloc+0x93/0x100 net/core/sock.c:1771
[<      none      >] do_ipv6_setsockopt.isra.5+0x1f43/0x2e50
net/ipv6/ipv6_sockglue.c:490
[<      none      >] ipv6_setsockopt+0x4f/0x150 net/ipv6/ipv6_sockglue.c:895
[<      none      >] sctp_setsockopt+0x194/0x4020 net/sctp/socket.c:3702
[<      none      >] sock_common_setsockopt+0xb4/0x140 net/core/sock.c:2641
[<     inline     >] SYSC_setsockopt net/socket.c:1750
[<      none      >] SyS_setsockopt+0x161/0x290 net/socket.c:1729
[<      none      >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in rcu_process_callbacks+0x52c/0x19e0 age=16 cpu=0 pid=0
[<      none      >] __slab_free+0x21e/0x3e0 mm/slub.c:2678
[<     inline     >] slab_free mm/slub.c:2833
[<      none      >] kfree+0x26f/0x3e0 mm/slub.c:3662
[<     inline     >] __rcu_reclaim kernel/rcu/rcu.h:113
[<     inline     >] rcu_do_batch kernel/rcu/tree.c:2693
[<     inline     >] invoke_rcu_callbacks kernel/rcu/tree.c:2961
[<     inline     >] __rcu_process_callbacks kernel/rcu/tree.c:2928
[<      none      >] rcu_process_callbacks+0x52c/0x19e0 kernel/rcu/tree.c:2945
[<      none      >] __do_softirq+0x2e5/0xb40 kernel/softirq.c:273
[<     inline     >] invoke_softirq kernel/softirq.c:350
[<      none      >] irq_exit+0x165/0x1e0 kernel/softirq.c:391
[<     inline     >] exiting_irq ./arch/x86/include/asm/apic.h:653
[<      none      >] smp_apic_timer_interrupt+0x88/0xc0
arch/x86/kernel/apic/apic.c:926
[<      none      >] apic_timer_interrupt+0x8c/0xa0
arch/x86/entry/entry_64.S:520
[<     inline     >] arch_safe_halt ./arch/x86/include/asm/paravirt.h:111
[<      none      >] default_idle+0x22/0x300 arch/x86/kernel/process.c:304
[<      none      >] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:295
[<      none      >] default_idle_call+0x4f/0x80 kernel/sched/idle.c:92
[<     inline     >] cpuidle_idle_call kernel/sched/idle.c:156
[<     inline     >] cpu_idle_loop kernel/sched/idle.c:251
[<      none      >] cpu_startup_entry+0x481/0x690 kernel/sched/idle.c:299
[<      none      >] rest_init+0x1c7/0x1d0 init/main.c:412
[<      none      >] start_kernel+0x6cd/0x6f3 init/main.c:683
[<      none      >] x86_64_start_reservations+0x2a/0x2c
arch/x86/kernel/head64.c:195
[<      none      >] x86_64_start_kernel+0x176/0x185
arch/x86/kernel/head64.c:184

INFO: Slab 0xffffea0000d24500 objects=28 used=26 fp=0xffff8800349179b0
flags=0x1fffc0000004080
INFO: Object 0xffff8800349179b0 @offset=14768 fp=0xffff880034914000
CPU: 1 PID: 7001 Comm: executor Tainted: G    B           4.4.0-rc4+ #158
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 0000000000000001 ffff880062eef940 ffffffff82e0f6d8 0000000041b58ab3
 ffffffff87aa2c7d ffffffff82e0f626 ffff88006c051740 ffffffff87ac3e19
 ffff88003e804900 0000000000000008 ffff8800349179b0 ffff880062eef940

Call Trace:
 [<ffffffff818450f4>] __asan_report_load4_noabort+0x54/0x70
mm/kasan/report.c:294
 [<ffffffff85d61f17>] inet6_destroy_sock+0x177/0x1c0 net/ipv6/af_inet6.c:433
 [<ffffffff864df89d>] sctp_v6_destroy_sock+0x1d/0x20 net/sctp/socket.c:7389
 [<ffffffff856cf00d>] sk_common_release+0x7d/0x3e0 net/core/sock.c:2662
 [<ffffffff864e58fe>] sctp_close+0x5fe/0x9b0 net/sctp/socket.c:1541
 [<ffffffff85bfe691>] inet_release+0x111/0x270 net/ipv4/af_inet.c:413
 [<ffffffff85d60ce5>] inet6_release+0x55/0x90 net/ipv6/af_inet6.c:406
 [<ffffffff856b3b96>] sock_release+0x96/0x260 net/socket.c:571
 [<ffffffff856b3d76>] sock_close+0x16/0x20 net/socket.c:1022
 [<ffffffff8189d304>] __fput+0x244/0x860 fs/file_table.c:208
 [<ffffffff8189d9b5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff813e2dc0>] task_work_run+0x130/0x240 kernel/task_work.c:115
 [<     inline     >] exit_task_work include/linux/task_work.h:21
 [<ffffffff8137d1e5>] do_exit+0x885/0x3050 kernel/exit.c:750
 [<ffffffff8137fb0c>] do_group_exit+0xec/0x390 kernel/exit.c:880
 [<     inline     >] SYSC_exit_group kernel/exit.c:891
 [<ffffffff8137fdcd>] SyS_exit_group+0x1d/0x20 kernel/exit.c:889
 [<ffffffff86a924f6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
==================================================================

On commit aa53685549a2cfb5f175b0c4a20bc9aa1e5a1b85 (Nov 8).
Eric, this now includes your patches that you previously pointed me
to, and also https://patchwork.ozlabs.org/patch/553068/ on top of it.