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Medium severity5.5NVD Advisory· Published Mar 25, 2026· Updated Apr 27, 2026

CVE-2026-23374

CVE-2026-23374

Description

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

blktrace: fix __this_cpu_read/write in preemptible context

tracing_record_cmdline() internally uses __this_cpu_read() and __this_cpu_write() on the per-CPU variable trace_cmdline_save, and trace_save_cmdline() explicitly asserts preemption is disabled via lockdep_assert_preemption_disabled(). These operations are only safe when preemption is off, as they were designed to be called from the scheduler context (probe_wakeup_sched_switch() / probe_wakeup()).

__blk_add_trace() was calling tracing_record_cmdline(current) early in the blk_tracer path, before ring buffer reservation, from process context where preemption is fully enabled. This triggers the following using blktests/blktrace/002:

blktrace/002 (blktrace ftrace corruption with sysfs trace) [failed] runtime 0.367s ... 0.437s something found in dmesg: [ 81.211018] run blktests blktrace/002 at 2026-02-25 22:24:33 [ 81.239580] null_blk: disk nullb1 created [ 81.357294] BUG: using __this_cpu_read() in preemptible [00000000] code: dd/2516 [ 81.362842] caller is tracing_record_cmdline+0x10/0x40 [ 81.362872] CPU: 16 UID: 0 PID: 2516 Comm: dd Tainted: G N 7.0.0-rc1lblk+ #84 PREEMPT(full) [ 81.362877] Tainted: [N]=TEST [ 81.362878] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 81.362881] Call Trace: [ 81.362884] [ 81.362886] dump_stack_lvl+0x8d/0xb0 ... (See '/mnt/sda/blktests/results/nodev/blktrace/002.dmesg' for the entire message)

[ 81.211018] run blktests blktrace/002 at 2026-02-25 22:24:33 [ 81.239580] null_blk: disk nullb1 created [ 81.357294] BUG: using __this_cpu_read() in preemptible [00000000] code: dd/2516 [ 81.362842] caller is tracing_record_cmdline+0x10/0x40 [ 81.362872] CPU: 16 UID: 0 PID: 2516 Comm: dd Tainted: G N 7.0.0-rc1lblk+ #84 PREEMPT(full) [ 81.362877] Tainted: [N]=TEST [ 81.362878] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 81.362881] Call Trace: [ 81.362884] [ 81.362886] dump_stack_lvl+0x8d/0xb0 [ 81.362895] check_preemption_disabled+0xce/0xe0 [ 81.362902] tracing_record_cmdline+0x10/0x40 [ 81.362923] __blk_add_trace+0x307/0x5d0 [ 81.362934] ? lock_acquire+0xe0/0x300 [ 81.362940] ? iov_iter_extract_pages+0x101/0xa30 [ 81.362959] blk_add_trace_bio+0x106/0x1e0 [ 81.362968] submit_bio_noacct_nocheck+0x24b/0x3a0 [ 81.362979] ? lockdep_init_map_type+0x58/0x260 [ 81.362988] submit_bio_wait+0x56/0x90 [ 81.363009] __blkdev_direct_IO_simple+0x16c/0x250 [ 81.363026] ? __pfx_submit_bio_wait_endio+0x10/0x10 [ 81.363038] ? rcu_read_lock_any_held+0x73/0xa0 [ 81.363051] blkdev_read_iter+0xc1/0x140 [ 81.363059] vfs_read+0x20b/0x330 [ 81.363083] ksys_read+0x67/0xe0 [ 81.363090] do_syscall_64+0xbf/0xf00 [ 81.363102] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 81.363106] RIP: 0033:0x7f281906029d [ 81.363111] Code: 31 c0 e9 c6 fe ff ff 50 48 8d 3d 66 63 0a 00 e8 59 ff 01 00 66 0f 1f 84 00 00 00 00 00 80 3d 41 33 0e 00 00 74 17 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 5b c3 66 2e 0f 1f 84 00 00 00 00 00 48 83 ec [ 81.363113] RSP: 002b:00007ffca127dd48 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [ 81.363120] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f281906029d [ 81.363122] RDX: 0000000000001000 RSI: 0000559f8bfae000 RDI: 0000000000000000 [ 81.363123] RBP: 0000000000001000 R08: 0000002863a10a81 R09: 00007f281915f000 [ 81.363124] R10: 00007f2818f77b60 R11: 0000000000000246 R12: 0000559f8bfae000 [ 81.363126] R13: 0000000000000000 R14: 0000000000000000 R15: 000000000000000a [ 81.363142]

The same BUG fires from blk_add_trace_plug(), blk_add_trace_unplug(), and blk_add_trace_rq() paths as well.

The purpose of tracin ---truncated---

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

In the Linux kernel, blktrace call tracing_record_cmdline() in a preemptible context causes a BUG due to per-CPU operations that require preemption disabled.

Vulnerability

Analysis

CVE-2026-23374 is a kernel bug in the blktrace subsystem. The function __blk_add_trace() calls tracing_record_cmdline(current) from process context, where preemption is enabled. However, tracing_record_cmdline() internally uses __this_cpu_read() and __this_cpu_write() on trace_cmdline_save, and the related function trace_save_cmdline() explicitly asserts preemption is disabled via lockdep_assert_preemption_disabled(). These operations are only safe when preemption is off, as they were designed to be called from scheduler context (e.g., probe_wakeup_sched_switch()).

Exploitation

The issue is triggered in process context, for example by I/O operations that cause block trace events. The blktests/blktrace/002 test reproduces the BUG: BUG: using __this_cpu_read() in preemptible [00000000] code: dd/2516. An attacker with local access and the ability to trigger block I/O with blktrace enabled could potentially crash the system, leading to a denial-of-service condition. No authentication is required beyond local user access to perform I/O that reaches the tracepoint.

Impact

A successful exploit of this vulnerability causes a kernel BUG splat, which can lead to a system crash or hang. The CVSS v3 base score is 5.5 (Medium), reflecting the requirement for local access and the availability impact. An attacker could trigger the bug by running the bug repeatedly to exhaust system resources or cause downtime.

Mitigation

Patches are available from the Linux kernel stable tree, referenced as commits da46b5dfef48, e5584932ac1d, aaba6ee63ba6, and 59efa088752b [1][2][3][4]. These commits move the tracing_record_cmdline() call in __blk_add_trace() to a context where preemption is disabled, typically by ensuring the per-CPU operations are safe. Users should update to a kernel version containing these fixes.

References
  1. Making sure you're not a bot!
  2. Making sure you're not a bot!
  3. Making sure you're not a bot!
  4. Making sure you're not a bot!

AI Insight generated on May 18, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

11
  • Linux/Kernel9 versions
    cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*+ 8 more
    • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*range: >=3.8.1,<6.12.82
    • cpe:2.3:o:linux:linux_kernel:3.8:-:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*
    • cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*
  • Linux/blktracellm-create
  • Linux/Linux Kernel Rtllm-fuzzy

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

4

News mentions

0

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