CVE-2023-53492

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

netfilter: nf_tables: do not ignore genmask when looking up chain by id

When adding a rule to a chain referring to its ID, if that chain had been deleted on the same batch, the rule might end up referring to a deleted chain.

This will lead to a WARNING like following:

[ 33.098431] ------------[ cut here ]------------ [ 33.098678] WARNING: CPU: 5 PID: 69 at net/netfilter/nf_tables_api.c:2037 nf_tables_chain_destroy+0x23d/0x260 [ 33.099217] Modules linked in: [ 33.099388] CPU: 5 PID: 69 Comm: kworker/5:1 Not tainted 6.4.0+ #409 [ 33.099726] Workqueue: events nf_tables_trans_destroy_work [ 33.100018] RIP: 0010:nf_tables_chain_destroy+0x23d/0x260 [ 33.100306] Code: 8b 7c 24 68 e8 64 9c ed fe 4c 89 e7 e8 5c 9c ed fe 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d 31 c0 89 c6 89 c7 c3 cc cc cc cc <0f> 0b 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d 31 c0 89 c6 89 c7 [ 33.101271] RSP: 0018:ffffc900004ffc48 EFLAGS: 00010202 [ 33.101546] RAX: 0000000000000001 RBX: ffff888006fc0a28 RCX: 0000000000000000 [ 33.101920] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 33.102649] RBP: ffffc900004ffc78 R08: 0000000000000000 R09: 0000000000000000 [ 33.103018] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880135ef500 [ 33.103385] R13: 0000000000000000 R14: dead000000000122 R15: ffff888006fc0a10 [ 33.103762] FS: 0000000000000000(0000) GS:ffff888024c80000(0000) knlGS:0000000000000000 [ 33.104184] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 33.104493] CR2: 00007fe863b56a50 CR3: 00000000124b0001 CR4: 0000000000770ee0 [ 33.104872] PKRU: 55555554 [ 33.104999] Call Trace: [ 33.105113] <TASK> [ 33.105214] ? show_regs+0x72/0x90 [ 33.105371] ? __warn+0xa5/0x210 [ 33.105520] ? nf_tables_chain_destroy+0x23d/0x260 [ 33.105732] ? report_bug+0x1f2/0x200 [ 33.105902] ? handle_bug+0x46/0x90 [ 33.106546] ? exc_invalid_op+0x19/0x50 [ 33.106762] ? asm_exc_invalid_op+0x1b/0x20 [ 33.106995] ? nf_tables_chain_destroy+0x23d/0x260 [ 33.107249] ? nf_tables_chain_destroy+0x30/0x260 [ 33.107506] nf_tables_trans_destroy_work+0x669/0x680 [ 33.107782] ? mark_held_locks+0x28/0xa0 [ 33.107996] ? __pfx_nf_tables_trans_destroy_work+0x10/0x10 [ 33.108294] ? _raw_spin_unlock_irq+0x28/0x70 [ 33.108538] process_one_work+0x68c/0xb70 [ 33.108755] ? lock_acquire+0x17f/0x420 [ 33.108977] ? __pfx_process_one_work+0x10/0x10 [ 33.109218] ? do_raw_spin_lock+0x128/0x1d0 [ 33.109435] ? _raw_spin_lock_irq+0x71/0x80 [ 33.109634] worker_thread+0x2bd/0x700 [ 33.109817] ? __pfx_worker_thread+0x10/0x10 [ 33.110254] kthread+0x18b/0x1d0 [ 33.110410] ? __pfx_kthread+0x10/0x10 [ 33.110581] ret_from_fork+0x29/0x50 [ 33.110757] </TASK> [ 33.110866] irq event stamp: 1651 [ 33.111017] hardirqs last enabled at (1659): [<ffffffffa206a209>] __up_console_sem+0x79/0xa0 [ 33.111379] hardirqs last disabled at (1666): [<ffffffffa206a1ee>] __up_console_sem+0x5e/0xa0 [ 33.111740] softirqs last enabled at (1616): [<ffffffffa1f5d40e>] __irq_exit_rcu+0x9e/0xe0 [ 33.112094] softirqs last disabled at (1367): [<ffffffffa1f5d40e>] __irq_exit_rcu+0x9e/0xe0 [ 33.112453] ---[ end trace 0000000000000000 ]---

This is due to the nft_chain_lookup_byid ignoring the genmask. After this change, adding the new rule will fail as it will not find the chain.

A flaw was found in the Linux kernel's netfilter nf_tables implementation. When an nftables rule is added to a chain referred to by its ID and that chain was deleted earlier in the same nftables batch, the nft_chain_lookup_byid() function ignores the genmask, so the new rule may end up referring to an already-deleted chain. This triggers a kernel WARNING in nf_tables_chain_destroy() when the batch transaction is destroyed. Red Hat rates this flaw as having low security impact: exploitation requires local access with high privileges and high attack complexity, and the impact is limited to low integrity and availability effects with no confidentiality impact, as the verified consequence is a kernel WARNING caused by a rule referencing a deleted chain rather than memory corruption or privilege escalation. The kernel and kernel-rt packages in Red Hat Enterprise Linux 9 are affected, and the fix is deferred because the flaw has been rated as having low security impact; the residual risk is that a privileged local user could trigger a kernel WARNING or install a rule that references a deleted chain, and Red Hat may revisit this decision if new information changes the overall risk assessment. Red Hat Enterprise Linux 6, 7, 8, and 10, and Red Hat In-Vehicle OS are not affected because the vulnerable code is not present in those products. The NIST and CVE.org CVSSv3 base score of 7.8 is significantly higher than Red Hat's score of 3.0 (low); the upstream scoring applies a generic high-impact local kernel vector (C:H/I:H/A:H) that is not supported by the specific verified consequence of this defect.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.