Re: KASAN: use-after-free Read in crypto_destroy_tfm

[Dmitry Vyukov]

On Sat, May 26, 2018 at 7:40 PM, syzbot
<syzbot+352126a5be7ccb25754e@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    0644f186fc9d Merge tag 'for_linus' of git://git.kernel.org..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=102bc257800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=61c12b53c2a25ec4
> dashboard link: https://syzkaller.appspot.com/bug?extid=352126a5be7ccb25754e
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+352126a5be7ccb25754e@xxxxxxxxxxxxxxxxxxxxxxxxx

Eric, do you remember if we had any recent fixes for this?

> ==================================================================
> BUG: KASAN: use-after-free in crypto_destroy_tfm+0x2a3/0x300
> crypto/api.c:573
> Read of size 8 at addr ffff8801d9023238 by task syz-executor6/10078
>
> CPU: 1 PID: 10078 Comm: syz-executor6 Not tainted 4.17.0-rc2+ #19
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  print_address_description+0x6c/0x20b mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>  crypto_destroy_tfm+0x2a3/0x300 crypto/api.c:573
>  crypto_free_rng include/crypto/rng.h:122 [inline]
>  rng_release+0x18/0x20 crypto/algif_rng.c:124
>  alg_do_release crypto/af_alg.c:119 [inline]
>  alg_sock_destruct+0x92/0xe0 crypto/af_alg.c:362
>  __sk_destruct+0xff/0xa40 net/core/sock.c:1566
>  sk_destruct+0x78/0x90 net/core/sock.c:1601
>  __sk_free+0x22e/0x340 net/core/sock.c:1612
>  sk_free+0x42/0x50 net/core/sock.c:1623
>  sock_put include/net/sock.h:1664 [inline]
>  af_alg_release+0x6e/0x90 crypto/af_alg.c:126
>  sock_release+0x96/0x1b0 net/socket.c:594
>  sock_close+0x16/0x20 net/socket.c:1149
>  __fput+0x34d/0x890 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x1e4/0x290 kernel/task_work.c:113
>  exit_task_work include/linux/task_work.h:22 [inline]
>  do_exit+0x1aee/0x2730 kernel/exit.c:865
>  do_group_exit+0x16f/0x430 kernel/exit.c:968
>  get_signal+0x886/0x1960 kernel/signal.c:2469
>  do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
>  exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x455979
> RSP: 002b:00007f4f4bbc2c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: 0000000000000000 RBX: 00007f4f4bbc36d4 RCX: 0000000000455979
> RDX: 0000000000000001 RSI: 0000000000000117 RDI: 0000000000000014
> RBP: 000000000072bf50 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000204f7000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 0000000000000519 R14: 00000000006faaf8 R15: 0000000000000001
>
> Allocated by task 4484:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
>  __do_kmalloc_node mm/slab.c:3682 [inline]
>  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696
>  __kmalloc_reserve.isra.38+0x3a/0xe0 net/core/skbuff.c:137
>  __alloc_skb+0x14d/0x780 net/core/skbuff.c:205
>  alloc_skb include/linux/skbuff.h:987 [inline]
>  netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
>  netlink_sendmsg+0xb01/0xfa0 net/netlink/af_netlink.c:1876
>  sock_sendmsg_nosec net/socket.c:629 [inline]
>  sock_sendmsg+0xd5/0x120 net/socket.c:639
>  ___sys_sendmsg+0x805/0x940 net/socket.c:2117
>  __sys_sendmsg+0x115/0x270 net/socket.c:2155
>  __do_sys_sendmsg net/socket.c:2164 [inline]
>  __se_sys_sendmsg net/socket.c:2162 [inline]
>  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 4484:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>  set_track mm/kasan/kasan.c:460 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>  __cache_free mm/slab.c:3498 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3813
>  skb_free_head+0x99/0xc0 net/core/skbuff.c:550
>  skb_release_data+0x690/0x860 net/core/skbuff.c:570
>  skb_release_all+0x4a/0x60 net/core/skbuff.c:627
>  __kfree_skb net/core/skbuff.c:641 [inline]
>  consume_skb+0x18b/0x550 net/core/skbuff.c:701
>  netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
>  netlink_unicast+0x593/0x740 net/netlink/af_netlink.c:1336
>  netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901
>  sock_sendmsg_nosec net/socket.c:629 [inline]
>  sock_sendmsg+0xd5/0x120 net/socket.c:639
>  ___sys_sendmsg+0x805/0x940 net/socket.c:2117
>  __sys_sendmsg+0x115/0x270 net/socket.c:2155
>  __do_sys_sendmsg net/socket.c:2164 [inline]
>  __se_sys_sendmsg net/socket.c:2162 [inline]
>  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8801d9023200
>  which belongs to the cache kmalloc-1024 of size 1024
> The buggy address is located 56 bytes inside of
>  1024-byte region [ffff8801d9023200, ffff8801d9023600)
> The buggy address belongs to the page:
> page:ffffea0007640880 count:1 mapcount:0 mapping:ffff8801d9022000 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
> raw: 02fffc0000008100 ffff8801d9022000 0000000000000000 0000000100000007
> raw: ffffea0006ea5e20 ffffea00073785a0 ffff8801da800ac0 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801d9023100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801d9023180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>
>> ffff8801d9023200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>                                         ^
>  ffff8801d9023280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801d9023300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
>
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> syzbot.
>
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