In the Linux kernel, the following vulnerability has been resolved: dm: fix unconditional IO...

CVE-2025-38063 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

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().

Basic information

Type
unreviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
—
Source code
Not specified
Published (advisory)
2025-06-18 12:30:33 UTC
Updated
2026-05-12 15:30:53 UTC
NVD published
2025-06-18

EPSS Score

Score Percentile
0.08% 23.33%

CVSS Scores

Base score Version Severity Vector
5.5 3.1 —
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.

Identifiers

Type Value
GHSA GHSA-jcxc-rghj-26cf ↗
CVE CVE-2025-38063 ↗

References

cvelogic Threat Intelligence