Message-ID: <CACT4Y+aqJzZGP8q0F0eiCjm2CHcKSX_y2wzfrJvqcXSpnwQy=g@mail.gmail.com>
Date:   Tue, 2 Mar 2021 20:28:54 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+9ec037722d2603a9f52e@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>, dsahern@...nel.org,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Paul Moore <paul@...l-moore.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: KASAN: use-after-free Read in cipso_v4_genopt

On Tue, Mar 2, 2021 at 8:25 PM syzbot
<syzbot+9ec037722d2603a9f52e@...kaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    7a7fd0de Merge branch 'kmap-conversion-for-5.12' of git://..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13693866d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=779a2568b654c1c6
> dashboard link: https://syzkaller.appspot.com/bug?extid=9ec037722d2603a9f52e
> compiler:       Debian clang version 11.0.1-2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1576737ad00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=107bdcead00000

This wasn't arranged :)
But the reproducer indeed contains NLBL_CIPSOV4_C_REMOVE and is
repeated in a loop...


> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9ec037722d2603a9f52e@...kaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in cipso_v4_genopt+0x1078/0x1700 net/ipv4/cipso_ipv4.c:1784
> Read of size 1 at addr ffff8881437d5710 by task syz-executor557/8392
>
> CPU: 1 PID: 8392 Comm: syz-executor557 Not tainted 5.12.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x125/0x19e lib/dump_stack.c:120
>  print_address_description+0x5f/0x3a0 mm/kasan/report.c:232
>  __kasan_report mm/kasan/report.c:399 [inline]
>  kasan_report+0x15e/0x210 mm/kasan/report.c:416
>  cipso_v4_genopt+0x1078/0x1700 net/ipv4/cipso_ipv4.c:1784
>  cipso_v4_sock_setattr+0x7c/0x460 net/ipv4/cipso_ipv4.c:1866
>  netlbl_sock_setattr+0x28e/0x2f0 net/netlabel/netlabel_kapi.c:995
>  smack_netlbl_add security/smack/smack_lsm.c:2404 [inline]
>  smack_socket_post_create+0x13b/0x280 security/smack/smack_lsm.c:2774
>  security_socket_post_create+0x6f/0xd0 security/security.c:2122
>  __sock_create+0x62f/0x8c0 net/socket.c:1424
>  sock_create net/socket.c:1459 [inline]
>  __sys_socket+0xde/0x2d0 net/socket.c:1501
>  __do_sys_socket net/socket.c:1510 [inline]
>  __se_sys_socket net/socket.c:1508 [inline]
>  __x64_sys_socket+0x76/0x80 net/socket.c:1508
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x440999
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffcfe002d48 EFLAGS: 00000246 ORIG_RAX: 0000000000000029
> RAX: ffffffffffffffda RBX: 000000000000b3fc RCX: 0000000000440999
> RDX: 0000000000000002 RSI: 0000000000000003 RDI: 0000040000000002
> RBP: 0000000000000000 R08: 00007ffcfe002ee8 R09: 00007ffcfe002ee8
> R10: 0000000000000012 R11: 0000000000000246 R12: 00007ffcfe002d5c
> R13: 431bde82d7b634db R14: 00000000004ae018 R15: 00000000004004a0
>
> Allocated by task 1:
>  kasan_save_stack mm/kasan/common.c:38 [inline]
>  kasan_set_track mm/kasan/common.c:46 [inline]
>  set_alloc_info mm/kasan/common.c:427 [inline]
>  ____kasan_kmalloc+0xc2/0xf0 mm/kasan/common.c:506
>  kasan_kmalloc include/linux/kasan.h:233 [inline]
>  kmem_cache_alloc_trace+0x21b/0x340 mm/slub.c:2934
>  kmalloc include/linux/slab.h:554 [inline]
>  smk_cipso_doi+0x1af/0x4e0 security/smack/smackfs.c:696
>  init_smk_fs+0xe2/0x24e security/smack/smackfs.c:3010
>  do_one_initcall+0x12b/0x310 init/main.c:1226
>  do_initcall_level+0x14a/0x1f5 init/main.c:1299
>  do_initcalls+0x4b/0x8c init/main.c:1315
>  kernel_init_freeable+0x2e3/0x406 init/main.c:1537
>  kernel_init+0xd/0x290 init/main.c:1424
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
>
> Freed by task 0:
>  kasan_save_stack mm/kasan/common.c:38 [inline]
>  kasan_set_track+0x3d/0x70 mm/kasan/common.c:46
>  kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:357
>  ____kasan_slab_free+0x100/0x140 mm/kasan/common.c:360
>  kasan_slab_free include/linux/kasan.h:199 [inline]
>  slab_free_hook mm/slub.c:1562 [inline]
>  slab_free_freelist_hook+0x13a/0x200 mm/slub.c:1600
>  slab_free mm/slub.c:3161 [inline]
>  kfree+0xcf/0x2b0 mm/slub.c:4213
>  rcu_do_batch kernel/rcu/tree.c:2559 [inline]
>  rcu_core+0x7a0/0x1220 kernel/rcu/tree.c:2794
>  __do_softirq+0x318/0x714 kernel/softirq.c:345
>
> Last potentially related work creation:
>  kasan_save_stack+0x27/0x50 mm/kasan/common.c:38
>  kasan_record_aux_stack+0xee/0x120 mm/kasan/generic.c:345
>  __call_rcu kernel/rcu/tree.c:3039 [inline]
>  call_rcu+0x12f/0x8a0 kernel/rcu/tree.c:3114
>  cipso_v4_doi_remove+0x2e2/0x310 net/ipv4/cipso_ipv4.c:531
>  netlbl_cipsov4_remove+0x219/0x390 net/netlabel/netlabel_cipso_v4.c:715
>  genl_family_rcv_msg_doit net/netlink/genetlink.c:739 [inline]
>  genl_family_rcv_msg net/netlink/genetlink.c:783 [inline]
>  genl_rcv_msg+0xe4e/0x1280 net/netlink/genetlink.c:800
>  netlink_rcv_skb+0x190/0x3a0 net/netlink/af_netlink.c:2502
>  genl_rcv+0x24/0x40 net/netlink/genetlink.c:811
>  netlink_unicast_kernel net/netlink/af_netlink.c:1312 [inline]
>  netlink_unicast+0x786/0x940 net/netlink/af_netlink.c:1338
>  netlink_sendmsg+0x9ae/0xd50 net/netlink/af_netlink.c:1927
>  sock_sendmsg_nosec net/socket.c:654 [inline]
>  sock_sendmsg net/socket.c:674 [inline]
>  ____sys_sendmsg+0x519/0x800 net/socket.c:2350
>  ___sys_sendmsg net/socket.c:2404 [inline]
>  __sys_sendmsg+0x2bf/0x370 net/socket.c:2433
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The buggy address belongs to the object at ffff8881437d5700
>  which belongs to the cache kmalloc-64 of size 64
> The buggy address is located 16 bytes inside of
>  64-byte region [ffff8881437d5700, ffff8881437d5740)
> The buggy address belongs to the page:
> page:000000003e519aab refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881437d5b00 pfn:0x1437d5
> flags: 0x57ff00000000200(slab)
> raw: 057ff00000000200 ffffea000511ff88 ffffea00051d0a48 ffff888010841640
> raw: ffff8881437d5b00 0000000000200019 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8881437d5600: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>  ffff8881437d5680: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> >ffff8881437d5700: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>                          ^
>  ffff8881437d5780: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
>  ffff8881437d5800: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>

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