CVE-2021-47588

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

sit: do not call ipip6devfree() from sitinitnet()

ipip6devfree is sit dev->privdestructor, already called by registernetdevice() if something goes wrong.

Alternative would be to make ipip6devfree() robust against multiple invocations, but other drivers do not implement this strategy.

syzbot reported:

dstrelease underflow WARNING: CPU: 0 PID: 5059 at net/core/dst.c:173 dstrelease+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:dstrelease+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> dstcachedestroy+0x107/0x1e0 net/core/dstcache.c:160 ipip6devfree net/ipv6/sit.c:1414 [inline] sitinitnet+0x229/0x550 net/ipv6/sit.c:1936 opsinit+0x313/0x430 net/core/netnamespace.c:140 setupnet+0x35b/0x9d0 net/core/netnamespace.c:326 copynetns+0x359/0x5c0 net/core/netnamespace.c:470 createnewnamespaces+0x4ce/0xa00 kernel/nsproxy.c:110 unsharensproxynamespaces+0x11e/0x180 kernel/nsproxy.c:226 ksysunshare+0x57d/0xb50 kernel/fork.c:3075 _dosysunshare kernel/fork.c:3146 [inline] _sesysunshare kernel/fork.c:3144 [inline] _x64sysunshare+0x34/0x40 kernel/fork.c:3144 dosyscallx64 arch/x86/entry/common.c:50 [inline] dosyscall64+0x44/0xd0 arch/x86/entry/common.c:80 entrySYSCALL64afterhwframe+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 ORIGRAX: 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>