use-after-free in hash_sock_destruct

From: Dmitry Vyukov
Date: Thu Dec 17 2015 - 08:00:22 EST

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Hello,

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

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

struct sockaddr_alg {
unsigned short salg_family;
char salg_type[14];
unsigned salg_feat;
unsigned salg_mask;
char salg_name[64];
};

int fd;

void *thr0(void *arg)
{
struct sockaddr_alg sa = {};
sa.salg_family = 0x26;
memcpy(sa.salg_type,
"\x68\x61\x73\x68\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 14);
sa.salg_feat = 0xf;
sa.salg_mask = 0x100;
memcpy(sa.salg_name,
"\x6d\x64\x34\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
64);
bind(fd, (struct sockaddr*)&sa, sizeof(sa));
return 0;
}

void *thr1(void *arg)
{
accept4(fd, 0, 0, 0x800ul);
return 0;
}

int main()
{
fd = socket(PF_ALG, SOCK_SEQPACKET, 0);
pthread_t th[4];
pthread_create(&th[0], 0, thr0, 0);
pthread_create(&th[1], 0, thr1, 0);
pthread_create(&th[2], 0, thr0, 0);
pthread_create(&th[3], 0, thr1, 0);
pthread_join(th[0], 0);
pthread_join(th[1], 0);
pthread_join(th[2], 0);
pthread_join(th[3], 0);
return 0;
}

==================================================================
BUG: KASAN: use-after-free in hash_sock_destruct+0x1de/0x260 at addr
ffff88005f057090
Read of size 8 by task a.out/6844
=============================================================================
BUG kmalloc-192 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------

Disabling lock debugging due to kernel taint
INFO: Allocated in crypto_create_tfm+0x87/0x2a0 age=3 cpu=2 pid=6845
[< none >] ___slab_alloc+0x648/0x8c0 mm/slub.c:2438
[< none >] __slab_alloc+0x4c/0x90 mm/slub.c:2467
[< inline >] slab_alloc_node mm/slub.c:2530
[< inline >] slab_alloc mm/slub.c:2572
[< none >] __kmalloc+0x2d9/0x480 mm/slub.c:3532
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:602
[< none >] crypto_create_tfm+0x87/0x2a0 crypto/api.c:470
[< none >] crypto_alloc_tfm+0x138/0x3f0 crypto/api.c:555
[< none >] crypto_alloc_ahash+0x2c/0x40 crypto/ahash.c:538
[< none >] hash_bind+0x25/0x30 crypto/algif_hash.c:240
[< none >] alg_bind+0x1a9/0x410 crypto/af_alg.c:155
[< none >] SYSC_bind+0x20a/0x2c0 net/socket.c:1383
[< none >] SyS_bind+0x24/0x30 net/socket.c:1369
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in kzfree+0x28/0x30 age=2 cpu=1 pid=6847
[< none >] __slab_free+0x21e/0x3e0 mm/slub.c:2648
[< inline >] slab_free mm/slub.c:2803
[< none >] kfree+0x26f/0x3e0 mm/slub.c:3632
[< none >] kzfree+0x28/0x30 mm/slab_common.c:1270
[< none >] crypto_destroy_tfm+0xdd/0x1e0 crypto/api.c:596
[< inline >] crypto_free_ahash include/crypto/hash.h:258
[< none >] hash_release+0x19/0x20 crypto/algif_hash.c:245
[< inline >] alg_do_release crypto/af_alg.c:116
[< none >] alg_bind+0x26a/0x410 crypto/af_alg.c:170
[< none >] SYSC_bind+0x20a/0x2c0 net/socket.c:1383
[< none >] SyS_bind+0x24/0x30 net/socket.c:1369
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Slab 0xffffea00017c1580 objects=16 used=15 fp=0xffff88005f057000
flags=0x5fffc0000004080
INFO: Object 0xffff88005f057000 @offset=4096 fp=0x (null)
CPU: 1 PID: 6844 Comm: a.out Tainted: G B 4.4.0-rc3+ #151
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
0000000000000001 ffff8800379779e0 ffffffff82e0f4b8 0000000041b58ab3
ffffffff87a9a265 ffffffff82e0f406 ffff88003d8c0000 ffffffff87abb3aa
ffff88003e804a00 0000000000000008 ffff88005f057000 ffff8800379779e0

Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff82e0f4b8>] dump_stack+0xb2/0xfa lib/dump_stack.c:50
[<ffffffff8183680c>] print_trailer+0x12c/0x210 mm/slub.c:652
[<ffffffff8184162f>] object_err+0x2f/0x40 mm/slub.c:659
[< inline >] print_address_description mm/kasan/report.c:138
[<ffffffff81845399>] kasan_report_error+0x5d9/0x860 mm/kasan/report.c:251
[< inline >] kasan_report mm/kasan/report.c:274
[<ffffffff818457c4>] __asan_report_load8_noabort+0x54/0x70
mm/kasan/report.c:295
[< inline >] crypto_ahash_digestsize include/crypto/hash.h:290
[<ffffffff82d2a7ae>] hash_sock_destruct+0x1de/0x260 crypto/algif_hash.c:259
[<ffffffff856c9255>] sk_destruct+0xa5/0x5f0 net/core/sock.c:1446
[<ffffffff856c982c>] __sk_free+0x8c/0x260 net/core/sock.c:1474
[<ffffffff856c9a30>] sk_free+0x30/0x40 net/core/sock.c:1485
[< inline >] sock_put include/net/sock.h:1625
[<ffffffff82d26c50>] af_alg_release+0x60/0x90 crypto/af_alg.c:123
[<ffffffff856b06b6>] sock_release+0x96/0x260 net/socket.c:571
[<ffffffff856b0896>] sock_close+0x16/0x20 net/socket.c:1022
[<ffffffff8189d9e4>] __fput+0x244/0x860 fs/file_table.c:208
[<ffffffff8189e095>] ____fput+0x15/0x20 fs/file_table.c:244
[<ffffffff813e34d0>] task_work_run+0x130/0x240 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[<ffffffff8137d8f5>] do_exit+0x885/0x3050 kernel/exit.c:750
[<ffffffff8138021c>] do_group_exit+0xec/0x390 kernel/exit.c:880
[< inline >] SYSC_exit_group kernel/exit.c:891
[<ffffffff813804dd>] SyS_exit_group+0x1d/0x20 kernel/exit.c:889
[<ffffffff86a89fb6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
==================================================================
BUG: unable to handle kernel paging request at fffffffffffffff8
IP: [<ffffffff82d2a6ae>] hash_sock_destruct+0xde/0x260 crypto/algif_hash.c:258
PGD 7c2f067 PUD 7c31067 PMD 0
Oops: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 1 PID: 6844 Comm: a.out Tainted: G B 4.4.0-rc3+ #151
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff88003d8c0000 ti: ffff880037970000 task.ti: ffff880037970000
RIP: 0010:[<ffffffff82d2a6ae>] [<ffffffff82d2a6ae>]
hash_sock_destruct+0xde/0x260
RSP: 0018:ffff880037977b30 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff88005f94dc80 RCX: 0000000000000001
RDX: 1fffffffffffffff RSI: 0000000000000001 RDI: 0000000000000282
RBP: ffff880037977b58 R08: 0000000000000001 R09: 0000000000000000
R10: ffffed0006f2ef55 R11: 0000000000000000 R12: ffff88005f94e5c0
R13: 0000000000000000 R14: fffffffffffffff8 R15: ffffffff856b0880
FS: 0000000000000000(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: fffffffffffffff8 CR3: 0000000007c2e000 CR4: 00000000000006e0
Stack:
ffff880000000000 ffff88005f94e5c0 ffffffff82d2a5d0 1ffff10006f2ef6d
0000000000000000 ffff880037977bf0 ffffffff856c9255 0000000041b58ab3
ffffffff87a9a273 ffffffff856c91b0 ffff8800602c8610 ffff88003d8c0000
Call Trace:
[<ffffffff856c9255>] sk_destruct+0xa5/0x5f0 net/core/sock.c:1446
[<ffffffff856c982c>] __sk_free+0x8c/0x260 net/core/sock.c:1474
[<ffffffff856c9a30>] sk_free+0x30/0x40 net/core/sock.c:1485
[< inline >] sock_put include/net/sock.h:1625
[<ffffffff82d26c50>] af_alg_release+0x60/0x90 crypto/af_alg.c:123
[<ffffffff856b06b6>] sock_release+0x96/0x260 net/socket.c:571
[<ffffffff856b0896>] sock_close+0x16/0x20 net/socket.c:1022
[<ffffffff8189d9e4>] __fput+0x244/0x860 fs/file_table.c:208
[<ffffffff8189e095>] ____fput+0x15/0x20 fs/file_table.c:244
[<ffffffff813e34d0>] task_work_run+0x130/0x240 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[<ffffffff8137d8f5>] do_exit+0x885/0x3050 kernel/exit.c:750
[<ffffffff8138021c>] do_group_exit+0xec/0x390 kernel/exit.c:880
[< inline >] SYSC_exit_group kernel/exit.c:891
[<ffffffff813804dd>] SyS_exit_group+0x1d/0x20 kernel/exit.c:889
[<ffffffff86a89fb6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
Code: 08 0f 84 7c 01 00 00 4c 89 f2 48 b8 00 00 00 00 00 fc ff df 48
c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e d4 00 00 00 48 85 db <41>
8b 55 f8 0f 84 35 01 00 00 48 8d bb 30 03 00 00 48 b8 00 00
RIP [<ffffffff82d2a6ae>] hash_sock_destruct+0xde/0x260 crypto/algif_hash.c:258
RSP <ffff880037977b30>
CR2: fffffffffffffff8
---[ end trace b367ebac5d601601 ]---
Fixing recursive fault but reboot is needed!

On upstream commit 31ade3b83e1821da5fbb2f11b5b3d4ab2ec39db8 (Nov 29).
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