CVE-2025-38063
Analyzed Analyzed - Analysis Complete
BaseFortify

Publication date: 2025-06-18

Last updated on: 2025-12-17

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: dm: fix unconditional IO throttle caused by REQ_PREFLUSH When a bio with REQ_PREFLUSH is submitted to dm, __send_empty_flush() generates a flush_bio with REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC, which causes the flush_bio to be throttled by wbt_wait(). An example from v5.4, similar problem also exists in upstream: crash> bt 2091206 PID: 2091206 TASK: ffff2050df92a300 CPU: 109 COMMAND: "kworker/u260:0" #0 [ffff800084a2f7f0] __switch_to at ffff80004008aeb8 #1 [ffff800084a2f820] __schedule at ffff800040bfa0c4 #2 [ffff800084a2f880] schedule at ffff800040bfa4b4 #3 [ffff800084a2f8a0] io_schedule at ffff800040bfa9c4 #4 [ffff800084a2f8c0] rq_qos_wait at ffff8000405925bc #5 [ffff800084a2f940] wbt_wait at ffff8000405bb3a0 #6 [ffff800084a2f9a0] __rq_qos_throttle at ffff800040592254 #7 [ffff800084a2f9c0] blk_mq_make_request at ffff80004057cf38 #8 [ffff800084a2fa60] generic_make_request at ffff800040570138 #9 [ffff800084a2fae0] submit_bio at ffff8000405703b4 #10 [ffff800084a2fb50] xlog_write_iclog at ffff800001280834 [xfs] #11 [ffff800084a2fbb0] xlog_sync at ffff800001280c3c [xfs] #12 [ffff800084a2fbf0] xlog_state_release_iclog at ffff800001280df4 [xfs] #13 [ffff800084a2fc10] xlog_write at ffff80000128203c [xfs] #14 [ffff800084a2fcd0] xlog_cil_push at ffff8000012846dc [xfs] #15 [ffff800084a2fda0] xlog_cil_push_work at ffff800001284a2c [xfs] #16 [ffff800084a2fdb0] process_one_work at ffff800040111d08 #17 [ffff800084a2fe00] worker_thread at ffff8000401121cc #18 [ffff800084a2fe70] kthread at ffff800040118de4 After commit 2def2845cc33 ("xfs: don't allow log IO to be throttled"), the metadata submitted by xlog_write_iclog() should not be throttled. But due to the existence of the dm layer, throttling flush_bio indirectly causes the metadata bio to be throttled. Fix this by conditionally adding REQ_IDLE to flush_bio.bi_opf, which makes wbt_should_throttle() return false to avoid wbt_wait().
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Meta Information
Published
2025-06-18
Last Modified
2025-12-17
Generated
2026-05-07
AI Q&A
2025-06-18
EPSS Evaluated
2026-05-05
NVD
CVE-2025-38063
Affected Vendors & Products
Showing 5 associated CPEs
Vendor Product Version / Range
linux linux_kernel to 6.1.141 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.93 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.31 (exc)
linux linux_kernel From 6.13 (inc) to 6.14.9 (exc)
debian debian_linux 11.0
Helpful Resources
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CWE
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CWE ID Description
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel's device mapper (dm) layer where an unconditional IO throttle happens due to the handling of REQ_PREFLUSH requests. When a bio with REQ_PREFLUSH is submitted, the function __send_empty_flush() generates a flush_bio with flags that cause it to be throttled by the writeback throttling mechanism (wbt_wait()). This unintended throttling delays flush operations, which can affect metadata writes, such as those from the xfs filesystem, causing performance issues or potential system instability. The fix involves adding the REQ_IDLE flag to the flush_bio operation flags to prevent throttling by wbt_wait().


How can this vulnerability impact me? :

This vulnerability can cause unintended delays in IO flush operations, particularly affecting metadata writes in filesystems like xfs. This can lead to degraded system performance, increased latency in IO operations, and potentially impact system stability or data integrity under heavy IO load conditions.


What immediate steps should I take to mitigate this vulnerability?

Update the Linux kernel to a version that includes the fix for this vulnerability, specifically the commit that conditionally adds REQ_IDLE to flush_bio.bi_opf to prevent IO throttling caused by REQ_PREFLUSH. This will avoid the issue where flush_bio is throttled by wbt_wait().


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