CVE-2021-47588

In the Linux kernel, the following vulnerability has been resolved:

sit: do not call ipip6_dev_free() from sit_init_net()

ipip6_dev_free is sit dev->priv_destructor, already called

by register_netdevice() if something goes wrong.

Alternative would be to make ipip6_dev_free() robust against

multiple invocations, but other drivers do not implement this

strategy.

syzbot reported:

dst_release underflow

WARNING: CPU: 0 PID: 5059 at net/core/dst.c:173 dst_release+0xd8/0xe0 net/core/dst.c:173

Modules linked in:

CPU: 1 PID: 5059 Comm: syz-executor.4 Not tainted 5.16.0-rc5-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

RIP: 0010:dst_release+0xd8/0xe0 net/core/dst.c:173

Code: 4c 89 f2 89 d9 31 c0 5b 41 5e 5d e9 da d5 44 f9 e8 1d 90 5f f9 c6 05 87 48 c6 05 01 48 c7 c7 80 44 99 8b 31 c0 e8 e8 67 29 f9 <0f> 0b eb 85 0f 1f 40 00 53 48 89 fb e8 f7 8f 5f f9 48 83 c3 a8 48

RSP: 0018:ffffc9000aa5faa0 EFLAGS: 00010246

RAX: d6894a925dd15a00 RBX: 00000000ffffffff RCX: 0000000000040000

RDX: ffffc90005e19000 RSI: 000000000003ffff RDI: 0000000000040000

RBP: 0000000000000000 R08: ffffffff816a1f42 R09: ffffed1017344f2c

R10: ffffed1017344f2c R11: 0000000000000000 R12: 0000607f462b1358

R13: 1ffffffff1bfd305 R14: ffffe8ffffcb1358 R15: dffffc0000000000

FS: 00007f66c71a2700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f88aaed5058 CR3: 0000000023e0f000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000

DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Call Trace:

<TASK>

dst_cache_destroy+0x107/0x1e0 net/core/dst_cache.c:160

ipip6_dev_free net/ipv6/sit.c:1414 [inline]

sit_init_net+0x229/0x550 net/ipv6/sit.c:1936

ops_init+0x313/0x430 net/core/net_namespace.c:140

setup_net+0x35b/0x9d0 net/core/net_namespace.c:326

copy_net_ns+0x359/0x5c0 net/core/net_namespace.c:470

create_new_namespaces+0x4ce/0xa00 kernel/nsproxy.c:110

unshare_nsproxy_namespaces+0x11e/0x180 kernel/nsproxy.c:226

ksys_unshare+0x57d/0xb50 kernel/fork.c:3075

__do_sys_unshare kernel/fork.c:3146 [inline]

__se_sys_unshare kernel/fork.c:3144 [inline]

__x64_sys_unshare+0x34/0x40 kernel/fork.c:3144

do_syscall_x64 arch/x86/entry/common.c:50 [inline]

do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80

entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x7f66c882ce99

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 bc ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f66c71a2168 EFLAGS: 00000246 ORIG_RAX: 0000000000000110

RAX: ffffffffffffffda RBX: 00007f66c893ff60 RCX: 00007f66c882ce99

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000048040200

RBP: 00007f66c8886ff1 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fff6634832f R14: 00007f66c71a2300 R15: 0000000000022000

</TASK>