Описание
In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list Kijo analyzed another race in the POSIX CPU timer code: Commit bf635681c906 converted cpu_timer::firing from a tristate value to a boolean. This lost the distinction between "not owned by the firing list" and "still owned, but delivery was canceled". The resulting race is: expiry handler timer_settime() timer_delete()
collect timer onto
private firing list
firing = true
observes firing = true
firing = false
return TIMER_RETRY
wait for handler
observes firing = false
finish deletion
unhash and free timer
resume list traversal
read freed elist.next
-> UAF
The firing bit is clearly the wrong indicator since that commit.
Check whether the timer is queued on the expiry list or not instead. If it
is queued clear the firing bit to prevent signal delivery as before and
return TIMER_RETRY so the caller unlocks the timer which allows the expiry
code to make progress and remove it from the list.
A flaw was found in the Linux kernel's POSIX CPU timer subsystem. A race condition can occur when modifying or deleting a timer concurrently with its expiration handling, allowing the timer to be freed while still queued on an active expiry list. A local user could exploit this use-after-free (UAF) flaw to cause a Denial of Service (DoS) via a system crash or potentially escalate privileges.
Отчет
Red Hat has evaluated this issue as having a Moderate severity impact because successful exploitation requires an authenticated local user to win a tight race condition during timer operations. The issue affects core kernel timer handling on newer releases such as Red Hat Enterprise Linux 10, while earlier platforms like RHEL 8 and 9 do not include the problematic code. Although the resulting memory corruption can destabilize the system or allow elevated access, the high execution complexity limits overall risk.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Affected | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Not affected |
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Дополнительная информация
Статус:
EPSS
7 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list Kijo analyzed another race in the POSIX CPU timer code: Commit bf635681c906 converted cpu_timer::firing from a tristate value to a boolean. This lost the distinction between "not owned by the firing list" and "still owned, but delivery was canceled". The resulting race is: expiry handler timer_settime() timer_delete() -------------- --------------- -------------- collect timer onto private firing list firing = true observes firing = true firing = false return TIMER_RETRY wait for handler observes firing = false finish deletion unhash and free timer resume list traversal read freed elist.next -> UAF The firing bit is clearly the wrong indicator since that commit. Check whether the timer is queued on the expiry list or not instead. If it is queued clear the firing bit to prevent signal delivery as befor...
In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list Kijo analyzed another race in the POSIX CPU timer code: Commit bf635681c906 converted cpu_timer::firing from a tristate value to a boolean. This lost the distinction between "not owned by the firing list" and "still owned, but delivery was canceled". The resulting race is: expiry handler timer_settime() timer_delete() -------------- --------------- -------------- collect timer onto private firing list firing = true observes firing = true firing = false return TIMER_RETRY wait for handler observes firing = false finish deletion
posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list
In the Linux kernel, the following vulnerability has been resolved: p ...
In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list Kijo analyzed another race in the POSIX CPU timer code: Commit bf635681c906 converted cpu_timer::firing from a tristate value to a boolean. This lost the distinction between "not owned by the firing list" and "still owned, but delivery was canceled". The resulting race is: expiry handler timer_settime() timer_delete() -------------- --------------- -------------- collect timer onto private firing list firing = true observes firing = true firing = false return TIMER_RETRY wait for handler observes firing = false finish deletion ...
EPSS
7 High
CVSS3