CVE-2024-26864

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

tcp: Fix refcnt handling in __inet_hash_connect().

syzbot reported a warning in sk_nulls_del_node_init_rcu().

The commit 66b60b0c8c4a (dccp/tcp: Unhash sk from ehash for tb2 alloc failure after check_estalblished().) tried to fix an issue that an unconnected socket occupies an ehash entry when bhash2 allocation fails.

In such a case, we need to revert changes done by check_established(), which does not hold refcnt when inserting socket into ehash.

So, to revert the change, we need to __sk_nulls_add_node_rcu() instead of sk_nulls_add_node_rcu().

Otherwise, sock_put() will cause refcnt underflow and leak the socket.

[0]: WARNING: CPU: 0 PID: 23948 at include/net/sock.h:799 sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799 Modules linked in: CPU: 0 PID: 23948 Comm: syz-executor.2 Not tainted 6.8.0-rc6-syzkaller-00159-gc055fc00c07b #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 RIP: 0010:sk_nulls_del_node_init_rcu+0x166/0x1a0 include/net/sock.h:799 Code: e8 7f 71 c6 f7 83 fb 02 7c 25 e8 35 6d c6 f7 4d 85 f6 0f 95 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 1b 6d c6 f7 90 <0f> 0b 90 eb b2 e8 10 6d c6 f7 4c 89 e7 be 04 00 00 00 e8 63 e7 d2 RSP: 0018:ffffc900032d7848 EFLAGS: 00010246 RAX: ffffffff89cd0035 RBX: 0000000000000001 RCX: 0000000000040000 RDX: ffffc90004de1000 RSI: 000000000003ffff RDI: 0000000000040000 RBP: 1ffff1100439ac26 R08: ffffffff89ccffe3 R09: 1ffff1100439ac28 R10: dffffc0000000000 R11: ffffed100439ac29 R12: ffff888021cd6140 R13: dffffc0000000000 R14: ffff88802a9bf5c0 R15: ffff888021cd6130 FS: 00007f3b823f16c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f3b823f0ff8 CR3: 000000004674a000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __inet_hash_connect+0x140f/0x20b0 net/ipv4/inet_hashtables.c:1139 dccp_v6_connect+0xcb9/0x1480 net/dccp/ipv6.c:956 __inet_stream_connect+0x262/0xf30 net/ipv4/af_inet.c:678 inet_stream_connect+0x65/0xa0 net/ipv4/af_inet.c:749 __sys_connect_file net/socket.c:2048 [inline] __sys_connect+0x2df/0x310 net/socket.c:2065 __do_sys_connect net/socket.c:2075 [inline] __se_sys_connect net/socket.c:2072 [inline] __x64_sys_connect+0x7a/0x90 net/socket.c:2072 do_syscall_64+0xf9/0x240 entry_SYSCALL_64_after_hwframe+0x6f/0x77 RIP: 0033:0x7f3b8167dda9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3b823f10c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007f3b817abf80 RCX: 00007f3b8167dda9 RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003 RBP: 00007f3b823f1120 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 000000000000000b R14: 00007f3b817abf80 R15: 00007ffd3beb57b8

Weakness

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.

Affected Software

Extended Description

There are many different kinds of mistakes that introduce information exposures. The severity of the error can range widely, depending on the context in which the product operates, the type of sensitive information that is revealed, and the benefits it may provide to an attacker. Some kinds of sensitive information include:

Information might be sensitive to different parties, each of which may have their own expectations for whether the information should be protected. These parties include:

Information exposures can occur in different ways:

It is common practice to describe any loss of confidentiality as an “information exposure,” but this can lead to overuse of CWE-200 in CWE mapping. From the CWE perspective, loss of confidentiality is a technical impact that can arise from dozens of different weaknesses, such as insecure file permissions or out-of-bounds read. CWE-200 and its lower-level descendants are intended to cover the mistakes that occur in behaviors that explicitly manage, store, transfer, or cleanse sensitive information.

Potential Mitigations

• Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
• Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/116.html
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References

• https://git.kernel.org/stable/c/04d9d1fc428ac9f581d55118d67e0cb546701feb
• https://git.kernel.org/stable/c/1b20e61d36f490319d3fbdedd410155232ab5190
• https://git.kernel.org/stable/c/856baaa100cd288d3685eedae9a129c996e7e755
• https://git.kernel.org/stable/c/86d9b040421bbd26425f5a3edc226f57ecdecbfe
• https://git.kernel.org/stable/c/ad105cde6b261b8b05ec872fe7d1987417d7fe5a