# CVE-2024-46704: linux: In the Linux kernel, the following vulnerability has been resolved:  workqueue: Fix spruious data race in __flush_wor...

CVE-2024-46704 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-46704, released September 13, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2024-46704
- Priority: Routine
- CVSS: 4.7 (medium)
- EPSS: 0.0018
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 13, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  workqueue: Fix spruious data race in __flush_work()  When flushing a work item for cancellation, __flush_work() knows that it exclusively owns the work item through its PENDING bit. 134874e2eee9 ("workqueue: Allow cancel_work_sync() and disable_work() from atomic contexts on BH work items") added a read of @work->data to determine whether to use busy wait for BH work items that are being canceled. While the read is safe when @from_cancel, @work->data was read before testing @from_cancel to simplify code structure:  	data = *work_data_bits(work); 	if (from_cancel && 	    !WARN_ON_ONCE(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_BH)) {  While the read data was never used if !@from_cancel, this could trigger KCSAN data race detection spuriously:    ==================================================================   BUG: KCSAN: data-race in __flush_work / __flush_work    write to 0xffff8881223aa3e8 of 8 bytes by task 3998 on cpu 0:    instrument_write include/linux/instrumented.h:41 [inline]    ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline]    insert_wq_barrier kernel/workqueue.c:3790 [inline]    start_flush_work kernel/workqueue.c:4142 [inline]    __flush_work+0x30b/0x570 kernel/workqueue.c:4178    flush_work kernel/workqueue.c:4229 [inline]    ...    read to 0xffff8881223aa3e8 of 8 bytes by task 50 on cpu 1:    __flush_work+0x42a/0x570 kernel/workqueue.c:4188    flush_work kernel/workqueue.c:4229 [inline]    flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251    ...    value changed: 0x0000000000400000 -> 0xffff88810006c00d  Reorganize the code so that @from_cancel is tested before @work->data is accessed. The only problem is triggering KCSAN detection spuriously. This shouldn't need READ_ONCE() or other access qualifiers.  No functional changes.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.10.7-1 | [DEBIAN-CVE-2024-46704](https://patchblox.com/security/data/fix/linux/debian-cve-2024-46704.md) | Sep 13, 2024 |
| Linux | linux Debian 14 | 6.10.7-1 | [DEBIAN-CVE-2024-46704](https://patchblox.com/security/data/fix/linux/debian-cve-2024-46704.md) | Sep 13, 2024 |

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