CVE-2024-36904

In the Linux kernel, the following vulnerability has been resolved: tcp:
Use refcount_inc_not_zero() in tcp_twsk_unique(). Anderson Nascimento
reported a use-after-free splat in tcp_twsk_unique() with nice analysis.
Since commit ec94c2696f0b (“tcp/dccp: avoid one atomic operation for
timewait hashdance”), inet_twsk_hashdance() sets TIME-WAIT socket’s
sk_refcnt after putting it into ehash and releasing the bucket lock. Thus,
there is a small race window where other threads could try to reuse the
port during connect() and call sock_hold() in tcp_twsk_unique() for the
TIME-WAIT socket with zero refcnt. If that happens, the refcnt taken by
tcp_twsk_unique() is overwritten and sock_put() will cause underflow,
triggering a real use-after-free somewhere else. To avoid the
use-after-free, we need to use refcount_inc_not_zero() in tcp_twsk_unique()
and give up on reusing the port if it returns false. [0]: refcount_t:
addition on 0; use-after-free. WARNING: CPU: 0 PID: 1039313 at
lib/refcount.c:25 refcount_warn_saturate+0xe5/0x110 CPU: 0 PID: 1039313
Comm: trigger Not tainted 6.8.6-200.fc39.x86_64 #1 Hardware name: VMware,
Inc. VMware20,1/440BX Desktop Reference Platform, BIOS
VMW201.00V.21805430.B64.2305221830 05/22/2023 RIP:
0010:refcount_warn_saturate+0xe5/0x110 Code: 42 8e ff 0f 0b c3 cc cc cc cc
80 3d aa 13 ea 01 00 0f 85 5e ff ff ff 48 c7 c7 f8 8e b7 82 c6 05 96 13 ea
01 01 e8 7b 42 8e ff <0f> 0b c3 cc cc cc cc 48 c7 c7 50 8f b7 82 c6 05 7a
13 ea 01 01 e8 RSP: 0018:ffffc90006b43b60 EFLAGS: 00010282 RAX:
0000000000000000 RBX: ffff888009bb3ef0 RCX: 0000000000000027 RDX:
ffff88807be218c8 RSI: 0000000000000001 RDI: ffff88807be218c0 RBP:
0000000000069d70 R08: 0000000000000000 R09: ffffc90006b439f0 R10:
ffffc90006b439e8 R11: 0000000000000003 R12: ffff8880029ede84 R13:
0000000000004e20 R14: ffffffff84356dc0 R15: ffff888009bb3ef0 FS:
00007f62c10926c0(0000) GS:ffff88807be00000(0000) knlGS:0000000000000000 CS:
0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020ccb000 CR3:
000000004628c005 CR4: 0000000000f70ef0 PKRU: 55555554 Call Trace: <TASK> ?
refcount_warn_saturate+0xe5/0x110 ? __warn+0x81/0x130 ?
refcount_warn_saturate+0xe5/0x110 ? report_bug+0x171/0x1a0 ?
refcount_warn_saturate+0xe5/0x110 ? handle_bug+0x3c/0x80 ?
exc_invalid_op+0x17/0x70 ? asm_exc_invalid_op+0x1a/0x20 ?
refcount_warn_saturate+0xe5/0x110 tcp_twsk_unique+0x186/0x190
__inet_check_established+0x176/0x2d0 __inet_hash_connect+0x74/0x7d0 ?
__pfx___inet_check_established+0x10/0x10 tcp_v4_connect+0x278/0x530
__inet_stream_connect+0x10f/0x3d0 inet_stream_connect+0x3a/0x60
__sys_connect+0xa8/0xd0 __x64_sys_connect+0x18/0x20
do_syscall_64+0x83/0x170 entry_SYSCALL_64_after_hwframe+0x78/0x80 RIP:
0033:0x7f62c11a885d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e
fa 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 8b 0d a3 45 0c 00 f7 d8 64 89 01 48 RSP:
002b:00007f62c1091e58 EFLAGS: 00000296 ORIG_RAX: 000000000000002a RAX:
ffffffffffffffda RBX: 0000000020ccb004 RCX: 00007f62c11a885d RDX:
0000000000000010 RSI: 0000000020ccb000 RDI: 0000000000000003 RBP:
00007f62c1091e90 R08: 0000000000000000 R09: 0000000000000000 R10:
0000000000000000 R11: 0000000000000296 R12: 00007f62c10926c0 R13:
ffffffffffffff88 R14: 0000000000000000 R15: 00007ffe237885b0 </TASK>