CVE-2025-21897
published 2025-04-01CVE-2025-21897: In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()…
PriorityP420medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
EPSS
0.14%
4.2th percentile
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()
a6250aa251ea ("sched_ext: Handle cases where pick_task_scx() is called
without preceding balance_scx()") added a workaround to handle the cases
where pick_task_scx() is called without prececing balance_scx() which is due
to a fair class bug where pick_taks_fair() may return NULL after a true
return from balance_fair().
The workaround detects when pick_task_scx() is called without preceding
balance_scx() and emulates SCX_RQ_BAL_KEEP and triggers kicking to avoid
stalling. Unfortunately, the workaround code was testing whether @prev was
on SCX to decide whether to keep the task running. This is incorrect as the
task may be on SCX but no longer runnable.
This could lead to a non-runnable task to be returned from pick_task_scx()
which cause interesting confusions and failures. e.g. A common failure mode
is the task ending up with (!on_rq && on_cpu) state which can cause
potential wakers to busy loop, which can easily lead to deadlocks.
Fix it by testing whether @prev has SCX_TASK_QUEUED set. This makes
@prev_on_scx only used in one place. Open code the usage and improve the
comment while at it.
Affected
11 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | linux | < linux 6.12.19-1 (forky) | linux 6.12.19-1 (forky) |
| linux | linux | — | — |
| linux | linux | >= a6250aa251eacaf3ebfcfe152a96a727fd483ecd < 5324c459f90d16b0c43a78b494c598915d782b7a | 5324c459f90d16b0c43a78b494c598915d782b7a |
| linux | linux | >= a6250aa251eacaf3ebfcfe152a96a727fd483ecd < de60a31cb0bcacfaf9487546eac5e70e0a9c66d7 | de60a31cb0bcacfaf9487546eac5e70e0a9c66d7 |
| linux | linux | >= a6250aa251eacaf3ebfcfe152a96a727fd483ecd < 8fef0a3b17bb258130a4fcbcb5addf94b25e9ec5 | 8fef0a3b17bb258130a4fcbcb5addf94b25e9ec5 |
| linux | linux_kernel | — | — |
| linux | linux_kernel | — | — |
| linux | linux_kernel | >= 0 < 6.12.19-1 | 6.12.19-1 |
| linux | linux_kernel | >= 0 < 6.12.19-1 | 6.12.19-1 |
| linux | linux_kernel | >= 6.12.1 < 6.12.18 | 6.12.18 |
| linux | linux_kernel | >= 6.13 < 6.13.6 | 6.13.6 |
CVSS provenance
nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM
vendor_debian5.5LOW
vendor_redhat5.5MEDIUM
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Red Hat
kernel: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()
vendor_redhat·2025-04-01·CVSS 5.5
CVE-2025-21897 [MEDIUM] kernel: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()
kernel: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()
a6250aa251ea ("sched_ext: Handle cases where pick_task_scx() is called
without preceding balance_scx()") added a workaround to handle the cases
where pick_task_scx() is called without prececing balance_scx() which is due
to a fair class bug where pick_taks_fair() may return NULL after a true
return from balance_fair().
The workaround detects when pick_task_scx() is called without preceding
balance_scx() and emulates SCX_RQ_BAL_KEEP and triggers kicking to avoid
stalling. Unfortunately, the workaround code was testing whether @prev was
Debian
CVE-2025-21897: linux - In the Linux kernel, the following vulnerability has been resolved: sched_ext: ...
vendor_debian·2025·CVSS 5.5
CVE-2025-21897 [MEDIUM] CVE-2025-21897: linux - In the Linux kernel, the following vulnerability has been resolved: sched_ext: ...
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance() a6250aa251ea ("sched_ext: Handle cases where pick_task_scx() is called without preceding balance_scx()") added a workaround to handle the cases where pick_task_scx() is called without prececing balance_scx() which is due to a fair class bug where pick_taks_fair() may return NULL after a true return from balance_fair(). The workaround detects when pick_task_scx() is called without preceding balance_scx() and emulates SCX_RQ_BAL_KEEP and triggers kicking to avoid stalling. Unfortunately, the workaround code was testing whether @prev was on SCX to decide whether to keep the task running. This is incorrect as the task may be on SCX but n
GHSA
GHSA-32g6-m5fv-fhv6: In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without
ghsa_unreviewed·2025-04-01
CVE-2025-21897 [MEDIUM] CWE-667 GHSA-32g6-m5fv-fhv6: In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()
a6250aa251ea ("sched_ext: Handle cases where pick_task_scx() is called
without preceding balance_scx()") added a workaround to handle the cases
where pick_task_scx() is called without prececing balance_scx() which is due
to a fair class bug where pick_taks_fair() may return NULL after a true
return from balance_fair().
The workaround detects when pick_task_scx() is called without preceding
balance_scx() and emulates SCX_RQ_BAL_KEEP and triggers kicking to avoid
stalling. Unfortunately, the workaround code was testing whether @prev was
on SCX to decide whether to keep the task running. This is incorrect as the
task may be on SCX bu
OSV
CVE-2025-21897: In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without b
osv·2025-04-01·CVSS 5.5
CVE-2025-21897 [MEDIUM] CVE-2025-21897: In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without b
In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance() a6250aa251ea ("sched_ext: Handle cases where pick_task_scx() is called without preceding balance_scx()") added a workaround to handle the cases where pick_task_scx() is called without prececing balance_scx() which is due to a fair class bug where pick_taks_fair() may return NULL after a true return from balance_fair(). The workaround detects when pick_task_scx() is called without preceding balance_scx() and emulates SCX_RQ_BAL_KEEP and triggers kicking to avoid stalling. Unfortunately, the workaround code was testing whether @prev was on SCX to decide whether to keep the task running. This is incorrect as the task may be on SCX but n
No detection rules found.
No public exploits indexed.
2025-04-01
Published