use-after-free in inet6_destroy_sock

From: Dmitry Vyukov
Date: Wed Dec 09 2015 - 09:16:20 EST

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.
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