CVE-2021-47178 (GCVE-0-2021-47178)

Vulnerability from cvelistv5 – Published: 2024-03-25 09:16 – Updated: 2026-08-05 08:46
VLAI
Title
scsi: target: core: Avoid smp_processor_id() in preemptible code
Summary
In the Linux kernel, the following vulnerability has been resolved: scsi: target: core: Avoid smp_processor_id() in preemptible code The BUG message "BUG: using smp_processor_id() in preemptible [00000000] code" was observed for TCMU devices with kernel config DEBUG_PREEMPT. The message was observed when blktests block/005 was run on TCMU devices with fileio backend or user:zbc backend [1]. The commit 1130b499b4a7 ("scsi: target: tcm_loop: Use LIO wq cmd submission helper") triggered the symptom. The commit modified work queue to handle commands and changed 'current->nr_cpu_allowed' at smp_processor_id() call. The message was also observed at system shutdown when TCMU devices were not cleaned up [2]. The function smp_processor_id() was called in SCSI host work queue for abort handling, and triggered the BUG message. This symptom was observed regardless of the commit 1130b499b4a7 ("scsi: target: tcm_loop: Use LIO wq cmd submission helper"). To avoid the preemptible code check at smp_processor_id(), get CPU ID with raw_smp_processor_id() instead. The CPU ID is used for performance improvement then thread move to other CPU will not affect the code. [1] [ 56.468103] run blktests block/005 at 2021-05-12 14:16:38 [ 57.369473] check_preemption_disabled: 85 callbacks suppressed [ 57.369480] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1511 [ 57.369506] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1510 [ 57.369512] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1506 [ 57.369552] caller is __target_init_cmd+0x157/0x170 [target_core_mod] [ 57.369606] CPU: 4 PID: 1506 Comm: fio Not tainted 5.13.0-rc1+ #34 [ 57.369613] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018 [ 57.369617] Call Trace: [ 57.369621] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1507 [ 57.369628] dump_stack+0x6d/0x89 [ 57.369642] check_preemption_disabled+0xc8/0xd0 [ 57.369628] caller is __target_init_cmd+0x157/0x170 [target_core_mod] [ 57.369655] __target_init_cmd+0x157/0x170 [target_core_mod] [ 57.369695] target_init_cmd+0x76/0x90 [target_core_mod] [ 57.369732] tcm_loop_queuecommand+0x109/0x210 [tcm_loop] [ 57.369744] scsi_queue_rq+0x38e/0xc40 [ 57.369761] __blk_mq_try_issue_directly+0x109/0x1c0 [ 57.369779] blk_mq_try_issue_directly+0x43/0x90 [ 57.369790] blk_mq_submit_bio+0x4e5/0x5d0 [ 57.369812] submit_bio_noacct+0x46e/0x4e0 [ 57.369830] __blkdev_direct_IO_simple+0x1a3/0x2d0 [ 57.369859] ? set_init_blocksize.isra.0+0x60/0x60 [ 57.369880] generic_file_read_iter+0x89/0x160 [ 57.369898] blkdev_read_iter+0x44/0x60 [ 57.369906] new_sync_read+0x102/0x170 [ 57.369929] vfs_read+0xd4/0x160 [ 57.369941] __x64_sys_pread64+0x6e/0xa0 [ 57.369946] ? lockdep_hardirqs_on+0x79/0x100 [ 57.369958] do_syscall_64+0x3a/0x70 [ 57.369965] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 57.369973] RIP: 0033:0x7f7ed4c1399f [ 57.369979] Code: 08 89 3c 24 48 89 4c 24 18 e8 7d f3 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 48 8b 74 24 08 8b 3c 24 b8 11 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 04 24 e8 cd f3 ff ff 48 8b [ 57.369983] RSP: 002b:00007ffd7918c580 EFLAGS: 00000293 ORIG_RAX: 0000000000000011 [ 57.369990] RAX: ffffffffffffffda RBX: 00000000015b4540 RCX: 00007f7ed4c1399f [ 57.369993] RDX: 0000000000001000 RSI: 00000000015de000 RDI: 0000000000000009 [ 57.369996] RBP: 00000000015b4540 R08: 0000000000000000 R09: 0000000000000001 [ 57.369999] R10: 0000000000e5c000 R11: 0000000000000293 R12: 00007f7eb5269a70 [ 57.370002] R13: 0000000000000000 R14: 0000000000001000 R15: 00000000015b4568 [ 57.370031] CPU: 7 PID: 1507 Comm: fio Not tainted 5.13.0-rc1+ #34 [ 57.370036] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018 [ 57.370039] Call Trace: [ 57.370045] dump_stack+0x6d/0x89 [ 57.370056] ch ---truncated---
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-09-10 15:54 UTC
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 008b936bbde3e87a611b3828a0d5d2a4f99026a0 , < a222d2794c53f8165de20aa91b39e35e4b72bce9 (git)
Affected: 1526d9f10c6184031e42afad0adbdde1213e8ad1 , < a20b6eaf4f35046a429cde57bee7eb5f13d6857f (git)
Affected: 1526d9f10c6184031e42afad0adbdde1213e8ad1 , < 70ca3c57ff914113f681e657634f7fbfa68e1ad1 (git)
Create a notification for this product.
Linux Linux Affected: 5.11
Unaffected: 0 , < 5.11 (semver)
Unaffected: 5.12.9 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: target: core: Avoid smp_processor_id() in preemptible code\n\nThe BUG message \"BUG: using smp_processor_id() in preemptible [00000000]\ncode\" was observed for TCMU devices with kernel config DEBUG_PREEMPT.\n\nThe message was observed when blktests block/005 was run on TCMU devices\nwith fileio backend or user:zbc backend [1]. The commit 1130b499b4a7\n(\"scsi: target: tcm_loop: Use LIO wq cmd submission helper\") triggered the\nsymptom. The commit modified work queue to handle commands and changed\n\u0027current-\u003enr_cpu_allowed\u0027 at smp_processor_id() call.\n\nThe message was also observed at system shutdown when TCMU devices were not\ncleaned up [2]. The function smp_processor_id() was called in SCSI host\nwork queue for abort handling, and triggered the BUG message. This symptom\nwas observed regardless of the commit 1130b499b4a7 (\"scsi: target:\ntcm_loop: Use LIO wq cmd submission helper\").\n\nTo avoid the preemptible code check at smp_processor_id(), get CPU ID with\nraw_smp_processor_id() instead. The CPU ID is used for performance\nimprovement then thread move to other CPU will not affect the code.\n\n[1]\n\n[   56.468103] run blktests block/005 at 2021-05-12 14:16:38\n[   57.369473] check_preemption_disabled: 85 callbacks suppressed\n[   57.369480] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1511\n[   57.369506] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1510\n[   57.369512] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1506\n[   57.369552] caller is __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369606] CPU: 4 PID: 1506 Comm: fio Not tainted 5.13.0-rc1+ #34\n[   57.369613] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018\n[   57.369617] Call Trace:\n[   57.369621] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1507\n[   57.369628]  dump_stack+0x6d/0x89\n[   57.369642]  check_preemption_disabled+0xc8/0xd0\n[   57.369628] caller is __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369655]  __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369695]  target_init_cmd+0x76/0x90 [target_core_mod]\n[   57.369732]  tcm_loop_queuecommand+0x109/0x210 [tcm_loop]\n[   57.369744]  scsi_queue_rq+0x38e/0xc40\n[   57.369761]  __blk_mq_try_issue_directly+0x109/0x1c0\n[   57.369779]  blk_mq_try_issue_directly+0x43/0x90\n[   57.369790]  blk_mq_submit_bio+0x4e5/0x5d0\n[   57.369812]  submit_bio_noacct+0x46e/0x4e0\n[   57.369830]  __blkdev_direct_IO_simple+0x1a3/0x2d0\n[   57.369859]  ? set_init_blocksize.isra.0+0x60/0x60\n[   57.369880]  generic_file_read_iter+0x89/0x160\n[   57.369898]  blkdev_read_iter+0x44/0x60\n[   57.369906]  new_sync_read+0x102/0x170\n[   57.369929]  vfs_read+0xd4/0x160\n[   57.369941]  __x64_sys_pread64+0x6e/0xa0\n[   57.369946]  ? lockdep_hardirqs_on+0x79/0x100\n[   57.369958]  do_syscall_64+0x3a/0x70\n[   57.369965]  entry_SYSCALL_64_after_hwframe+0x44/0xae\n[   57.369973] RIP: 0033:0x7f7ed4c1399f\n[   57.369979] Code: 08 89 3c 24 48 89 4c 24 18 e8 7d f3 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 48 8b 74 24 08 8b 3c 24 b8 11 00 00 00 0f 05 \u003c48\u003e 3d 00 f0 ff ff 77 31 44 89 c7 48 89 04 24 e8 cd f3 ff ff 48 8b\n[   57.369983] RSP: 002b:00007ffd7918c580 EFLAGS: 00000293 ORIG_RAX: 0000000000000011\n[   57.369990] RAX: ffffffffffffffda RBX: 00000000015b4540 RCX: 00007f7ed4c1399f\n[   57.369993] RDX: 0000000000001000 RSI: 00000000015de000 RDI: 0000000000000009\n[   57.369996] RBP: 00000000015b4540 R08: 0000000000000000 R09: 0000000000000001\n[   57.369999] R10: 0000000000e5c000 R11: 0000000000000293 R12: 00007f7eb5269a70\n[   57.370002] R13: 0000000000000000 R14: 0000000000001000 R15: 00000000015b4568\n[   57.370031] CPU: 7 PID: 1507 Comm: fio Not tainted 5.13.0-rc1+ #34\n[   57.370036] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018\n[   57.370039] Call Trace:\n[   57.370045]  dump_stack+0x6d/0x89\n[   57.370056]  ch\n---truncated---"
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              "value": "AV:N - __target_init_cmd() is shared target-core code invoked from network fabrics including iSCSI (iscsit_setup_scsi_cmd/iscsit_handle_task_mgt_cmd) on every SCSI/TMF PDU after session setup; an internet-facing or LAN iSCSI target is the primary deployment of this subsystem.\nAC:L - Every command initialization in preemptible context deterministically hits smp_processor_id()\u0027s DEBUG_PREEMPT check with no race or attacker-uncontrollable memory layout; the attacker fully controls command rate over an established session.\nPR:N - iSCSI commonly runs with authentication disabled (AuthMethod=None / authentication=0) and open ACLs, so a remote initiator can complete login and send SCSI commands with no credentials on the target host.\nUI:N - The attacker triggers the path by sending their own iSCSI SCSI/TMF PDUs; no separate victim action such as mounting or opening a file is required.\nS:U - Impact stays inside the host kernel target-core path under the same OS security authority, with no VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:N - check_preemption_disabled() only emits a rate-limited symbolic dump_stack(); smp_processor_id() still returns a valid CPU id with no OOB/UAF read, and the commit states CPU affinity is performance-only.\nI:N - raw_smp_processor_id() has identical value semantics for this snapshot use; cmd-\u003ecpuid only selects a per-CPU state_list/workqueue affinity hint and creates no write, corruption, or control-flow hijack primitive.\nA:H - The defect fires on the SCSI command hot path and emits a kernel BUG: report with full dump_stack() that a remote initiator can drive repeatedly, producing a sustained log/console printk storm that can stall I/O (matching hot-path DEBUG_PREEMPT SCSI precedent)."
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: target: core: Avoid smp_processor_id() in preemptible code\n\nThe BUG message \"BUG: using smp_processor_id() in preemptible [00000000]\ncode\" was observed for TCMU devices with kernel config DEBUG_PREEMPT.\n\nThe message was observed when blktests block/005 was run on TCMU devices\nwith fileio backend or user:zbc backend [1]. The commit 1130b499b4a7\n(\"scsi: target: tcm_loop: Use LIO wq cmd submission helper\") triggered the\nsymptom. The commit modified work queue to handle commands and changed\n\u0027current-\u003enr_cpu_allowed\u0027 at smp_processor_id() call.\n\nThe message was also observed at system shutdown when TCMU devices were not\ncleaned up [2]. The function smp_processor_id() was called in SCSI host\nwork queue for abort handling, and triggered the BUG message. This symptom\nwas observed regardless of the commit 1130b499b4a7 (\"scsi: target:\ntcm_loop: Use LIO wq cmd submission helper\").\n\nTo avoid the preemptible code check at smp_processor_id(), get CPU ID with\nraw_smp_processor_id() instead. The CPU ID is used for performance\nimprovement then thread move to other CPU will not affect the code.\n\n[1]\n\n[   56.468103] run blktests block/005 at 2021-05-12 14:16:38\n[   57.369473] check_preemption_disabled: 85 callbacks suppressed\n[   57.369480] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1511\n[   57.369506] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1510\n[   57.369512] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1506\n[   57.369552] caller is __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369606] CPU: 4 PID: 1506 Comm: fio Not tainted 5.13.0-rc1+ #34\n[   57.369613] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018\n[   57.369617] Call Trace:\n[   57.369621] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1507\n[   57.369628]  dump_stack+0x6d/0x89\n[   57.369642]  check_preemption_disabled+0xc8/0xd0\n[   57.369628] caller is __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369655]  __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369695]  target_init_cmd+0x76/0x90 [target_core_mod]\n[   57.369732]  tcm_loop_queuecommand+0x109/0x210 [tcm_loop]\n[   57.369744]  scsi_queue_rq+0x38e/0xc40\n[   57.369761]  __blk_mq_try_issue_directly+0x109/0x1c0\n[   57.369779]  blk_mq_try_issue_directly+0x43/0x90\n[   57.369790]  blk_mq_submit_bio+0x4e5/0x5d0\n[   57.369812]  submit_bio_noacct+0x46e/0x4e0\n[   57.369830]  __blkdev_direct_IO_simple+0x1a3/0x2d0\n[   57.369859]  ? set_init_blocksize.isra.0+0x60/0x60\n[   57.369880]  generic_file_read_iter+0x89/0x160\n[   57.369898]  blkdev_read_iter+0x44/0x60\n[   57.369906]  new_sync_read+0x102/0x170\n[   57.369929]  vfs_read+0xd4/0x160\n[   57.369941]  __x64_sys_pread64+0x6e/0xa0\n[   57.369946]  ? lockdep_hardirqs_on+0x79/0x100\n[   57.369958]  do_syscall_64+0x3a/0x70\n[   57.369965]  entry_SYSCALL_64_after_hwframe+0x44/0xae\n[   57.369973] RIP: 0033:0x7f7ed4c1399f\n[   57.369979] Code: 08 89 3c 24 48 89 4c 24 18 e8 7d f3 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 48 8b 74 24 08 8b 3c 24 b8 11 00 00 00 0f 05 \u003c48\u003e 3d 00 f0 ff ff 77 31 44 89 c7 48 89 04 24 e8 cd f3 ff ff 48 8b\n[   57.369983] RSP: 002b:00007ffd7918c580 EFLAGS: 00000293 ORIG_RAX: 0000000000000011\n[   57.369990] RAX: ffffffffffffffda RBX: 00000000015b4540 RCX: 00007f7ed4c1399f\n[   57.369993] RDX: 0000000000001000 RSI: 00000000015de000 RDI: 0000000000000009\n[   57.369996] RBP: 00000000015b4540 R08: 0000000000000000 R09: 0000000000000001\n[   57.369999] R10: 0000000000e5c000 R11: 0000000000000293 R12: 00007f7eb5269a70\n[   57.370002] R13: 0000000000000000 R14: 0000000000001000 R15: 00000000015b4568\n[   57.370031] CPU: 7 PID: 1507 Comm: fio Not tainted 5.13.0-rc1+ #34\n[   57.370036] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018\n[   57.370039] Call Trace:\n[   57.370045]  dump_stack+0x6d/0x89\n[   57.370056]  ch\n---truncated---"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: scsi: target: core: Evite smp_processor_id() en c\u00f3digo interrumpible Se observ\u00f3 el mensaje de ERROR \"ERROR: usar smp_processor_id() en c\u00f3digo interrumpible [00000000]\" para dispositivos TCMU con configuraci\u00f3n de kernel DEBUG_PREEMPT. El mensaje se observ\u00f3 cuando se ejecut\u00f3 blktests block/005 en dispositivos TCMU con backend fileio o usuario:zbc [1]. La confirmaci\u00f3n 1130b499b4a7 (\"scsi: target: tcm_loop: Use el asistente de env\u00edo LIO wq cmd\") desencaden\u00f3 el s\u00edntoma. La confirmaci\u00f3n modific\u00f3 la cola de trabajo para manejar comandos y cambi\u00f3 \u0027current-\u0026gt;nr_cpu_allowed\u0027 en la llamada a smp_processor_id(). El mensaje tambi\u00e9n se observ\u00f3 al apagar el sistema cuando los dispositivos TCMU no se limpiaron [2]. La funci\u00f3n smp_processor_id() fue llamada en la cola de trabajo del host SCSI para el manejo de abortos y activ\u00f3 el mensaje de ERROR. Este s\u00edntoma se observ\u00f3 independientemente de la confirmaci\u00f3n 1130b499b4a7 (\"scsi: target: tcm_loop: Use el asistente de env\u00edo LIO wq cmd\"). Para evitar la verificaci\u00f3n del c\u00f3digo interrumpible en smp_processor_id(), obtenga el ID de la CPU con raw_smp_processor_id() en su lugar. El ID de la CPU se utiliza para mejorar el rendimiento, luego el movimiento del subproceso a otra CPU no afectar\u00e1 el c\u00f3digo. [1] [56.468103] ejecute blktests block/005 el 2021-05-12 14:16:38 [57.369473] check_preemption_disabled: 85 devoluciones de llamada suprimidas [57.369480] ERROR: usar smp_processor_id() en c\u00f3digo preferente [00000000]: fio/151 1 [ 57.369506] ERROR: usar smp_processor_id() en c\u00f3digo interrumpible [00000000]: fio/1510 [57.369512] ERROR: usar smp_processor_id() en c\u00f3digo interrumpible [00000000]: fio/1506 [57.369552] la persona que llama es __target_init_cmd+0 x157/0x170 [objetivo_core_mod] [ 57.369606] CPU: 4 PID: 1506 Comm: fio Not tainted 5.13.0-rc1+ #34 [ 57.369613] Nombre del hardware: Fabricante del sistema Nombre del producto del sistema/PRIME Z270-A, BIOS 1302 15/03/2018 [ 57.369617] Seguimiento de llamadas : [57.369621] ERROR: usar smp_processor_id() en c\u00f3digo interrumpible [00000000]: fio/1507 [57.369628] dump_stack+0x6d/0x89 [57.369642] check_preemption_disabled+0xc8/0xd0 [57.369628] la persona que llama es __ target_init_cmd+0x157/0x170 [target_core_mod] [ 57.369655] __target_init_cmd+0x157/0x170 [target_core_mod] [ 57.369695] target_init_cmd+0x76/0x90 [target_core_mod] [ 57.369732] tcm_loop_queuecommand+0x109/0x210 [tcm_loop] [ 57 .369744] scsi_queue_rq+0x38e/0xc40 [ 57.369761] __blk_mq_try_issue_directly+0x109/0x1c0 [ 57.369779 ] blk_mq_try_issue_directly+0x43/0x90 [ 57.369790] blk_mq_submit_bio+0x4e5/0x5d0 [ 57.369812] submit_bio_noacct+0x46e/0x4e0 [ 57.369830] __blkdev_direct_IO_simple+0x1a3/0x2 d0 [57.369859]? set_init_blocksize.isra.0+0x60/0x60 [ 57.369880] generic_file_read_iter+0x89/0x160 [ 57.369898] blkdev_read_iter+0x44/0x60 [ 57.369906] new_sync_read+0x102/0x170 [ 57.369929 ] vfs_read+0xd4/0x160 [ 57.369941] __x64_sys_pread64+0x6e/0xa0 [ 57.369946] ? lockdep_hardirqs_on+0x79/0x100 [ 57.369958] do_syscall_64+0x3a/0x70 [ 57.369965] Entry_SYSCALL_64_after_hwframe+0x44/0xae [ 57.369973] RIP: 0033:0x7f7ed4c1399f [ 5 7.369979] C\u00f3digo: 08 89 3c 24 48 89 4c 24 18 e8 7d f3 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 48 8b 74 24 08 8b 3c 24 b8 11 00 00 00 0f 05 \u0026lt;48\u0026gt; 3d 00 f0 ff ff 77 31 44 89 c7 48 89 04 24 e8 cd f3 ff ff 48 8b [ 57.369983] RSP: 002b:00007ffd7918c580 EFLAGS: 00000293 ORIG_RAX: 0000000000000011 [ 57.369990] RAX: fffffffffffffffda RBX: 00000000015b4540 RCX: 00 007f7ed4c1399f [ 57.369993] RDX: 0000000000001000 RSI: 00000000015de000 RDI: 000000000000000009 [ 57.369996] RBP: 00000000015b4540 R08: 000 0000000000000 R09: 0000000000000001 [ 57.369999] R10: 0000000000e5c000 R11: 0000000000000293 R12: 00007f7eb5269a70 [ 57.370002] R13: 00000000000000000 R14: 000000000000 1000 R15: 00000000015b4568 [57.370031] CPU: 7 PID: 1507 ---truncado---"
          }
        ],
        "id": "CVE-2021-47178",
        "lastModified": "2026-08-04T10:16:50.490",
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            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: target: core: Avoid smp_processor_id() in preemptible code\n\nThe BUG message \"BUG: using smp_processor_id() in preemptible [00000000]\ncode\" was observed for TCMU devices with kernel config DEBUG_PREEMPT.\n\nThe message was observed when blktests block/005 was run on TCMU devices\nwith fileio backend or user:zbc backend [1]. The commit 1130b499b4a7\n(\"scsi: target: tcm_loop: Use LIO wq cmd submission helper\") triggered the\nsymptom. The commit modified work queue to handle commands and changed\n\u0027current-\u003enr_cpu_allowed\u0027 at smp_processor_id() call.\n\nThe message was also observed at system shutdown when TCMU devices were not\ncleaned up [2]. The function smp_processor_id() was called in SCSI host\nwork queue for abort handling, and triggered the BUG message. This symptom\nwas observed regardless of the commit 1130b499b4a7 (\"scsi: target:\ntcm_loop: Use LIO wq cmd submission helper\").\n\nTo avoid the preemptible code check at smp_processor_id(), get CPU ID with\nraw_smp_processor_id() instead. The CPU ID is used for performance\nimprovement then thread move to other CPU will not affect the code.\n\n[1]\n\n[   56.468103] run blktests block/005 at 2021-05-12 14:16:38\n[   57.369473] check_preemption_disabled: 85 callbacks suppressed\n[   57.369480] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1511\n[   57.369506] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1510\n[   57.369512] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1506\n[   57.369552] caller is __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369606] CPU: 4 PID: 1506 Comm: fio Not tainted 5.13.0-rc1+ #34\n[   57.369613] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018\n[   57.369617] Call Trace:\n[   57.369621] BUG: using smp_processor_id() in preemptible [00000000] code: fio/1507\n[   57.369628]  dump_stack+0x6d/0x89\n[   57.369642]  check_preemption_disabled+0xc8/0xd0\n[   57.369628] caller is __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369655]  __target_init_cmd+0x157/0x170 [target_core_mod]\n[   57.369695]  target_init_cmd+0x76/0x90 [target_core_mod]\n[   57.369732]  tcm_loop_queuecommand+0x109/0x210 [tcm_loop]\n[   57.369744]  scsi_queue_rq+0x38e/0xc40\n[   57.369761]  __blk_mq_try_issue_directly+0x109/0x1c0\n[   57.369779]  blk_mq_try_issue_directly+0x43/0x90\n[   57.369790]  blk_mq_submit_bio+0x4e5/0x5d0\n[   57.369812]  submit_bio_noacct+0x46e/0x4e0\n[   57.369830]  __blkdev_direct_IO_simple+0x1a3/0x2d0\n[   57.369859]  ? set_init_blocksize.isra.0+0x60/0x60\n[   57.369880]  generic_file_read_iter+0x89/0x160\n[   57.369898]  blkdev_read_iter+0x44/0x60\n[   57.369906]  new_sync_read+0x102/0x170\n[   57.369929]  vfs_read+0xd4/0x160\n[   57.369941]  __x64_sys_pread64+0x6e/0xa0\n[   57.369946]  ? lockdep_hardirqs_on+0x79/0x100\n[   57.369958]  do_syscall_64+0x3a/0x70\n[   57.369965]  entry_SYSCALL_64_after_hwframe+0x44/0xae\n[   57.369973] RIP: 0033:0x7f7ed4c1399f\n[   57.369979] Code: 08 89 3c 24 48 89 4c 24 18 e8 7d f3 ff ff 4c 8b 54 24 18 48 8b 54 24 10 41 89 c0 48 8b 74 24 08 8b 3c 24 b8 11 00 00 00 0f 05 \u003c48\u003e 3d 00 f0 ff ff 77 31 44 89 c7 48 89 04 24 e8 cd f3 ff ff 48 8b\n[   57.369983] RSP: 002b:00007ffd7918c580 EFLAGS: 00000293 ORIG_RAX: 0000000000000011\n[   57.369990] RAX: ffffffffffffffda RBX: 00000000015b4540 RCX: 00007f7ed4c1399f\n[   57.369993] RDX: 0000000000001000 RSI: 00000000015de000 RDI: 0000000000000009\n[   57.369996] RBP: 00000000015b4540 R08: 0000000000000000 R09: 0000000000000001\n[   57.369999] R10: 0000000000e5c000 R11: 0000000000000293 R12: 00007f7eb5269a70\n[   57.370002] R13: 0000000000000000 R14: 0000000000001000 R15: 00000000015b4568\n[   57.370031] CPU: 7 PID: 1507 Comm: fio Not tainted 5.13.0-rc1+ #34\n[   57.370036] Hardware name: System manufacturer System Product Name/PRIME Z270-A, BIOS 1302 03/15/2018\n[   57.370039] Call Trace:\n[   57.370045]  dump_stack+0x6d/0x89\n[   57.370056]  ch\n---truncated---"
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.5,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:N - __target_init_cmd() is shared target-core code invoked from network fabrics including iSCSI (iscsit_setup_scsi_cmd/iscsit_handle_task_mgt_cmd) on every SCSI/TMF PDU after session setup; an internet-facing or LAN iSCSI target is the primary deployment of this subsystem.\nAC:L - Every command initialization in preemptible context deterministically hits smp_processor_id()\u0027s DEBUG_PREEMPT check with no race or attacker-uncontrollable memory layout; the attacker fully controls command rate over an established session.\nPR:N - iSCSI commonly runs with authentication disabled (AuthMethod=None / authentication=0) and open ACLs, so a remote initiator can complete login and send SCSI commands with no credentials on the target host.\nUI:N - The attacker triggers the path by sending their own iSCSI SCSI/TMF PDUs; no separate victim action such as mounting or opening a file is required.\nS:U - Impact stays inside the host kernel target-core path under the same OS security authority, with no VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:N - check_preemption_disabled() only emits a rate-limited symbolic dump_stack(); smp_processor_id() still returns a valid CPU id with no OOB/UAF read, and the commit states CPU affinity is performance-only.\nI:N - raw_smp_processor_id() has identical value semantics for this snapshot use; cmd-\u003ecpuid only selects a per-CPU state_list/workqueue affinity hint and creates no write, corruption, or control-flow hijack primitive.\nA:H - The defect fires on the SCSI command hot path and emits a kernel BUG: report with full dump_stack() that a remote initiator can drive repeatedly, producing a sustained log/console printk storm that can stall I/O (matching hot-path DEBUG_PREEMPT SCSI precedent)."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-08-05T08:46:30.525Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/a222d2794c53f8165de20aa91b39e35e4b72bce9"
            },
            {
              "url": "https://git.kernel.org/stable/c/a20b6eaf4f35046a429cde57bee7eb5f13d6857f"
            },
            {
              "url": "https://git.kernel.org/stable/c/70ca3c57ff914113f681e657634f7fbfa68e1ad1"
            }
          ],
          "title": "scsi: target: core: Avoid smp_processor_id() in preemptible code",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2021-47178",
        "datePublished": "2024-03-25T09:16:28.024Z",
        "dateReserved": "2024-03-25T09:12:14.112Z",
        "dateUpdated": "2026-08-05T08:46:30.525Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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