Description
In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel

The following race is possible between bpf_timer_cancel_and_free
and bpf_timer_cancel. It will lead a UAF on the timer->timer.

bpf_timer_cancel();
spin_lock();
t = timer->time;
spin_unlock();

bpf_timer_cancel_and_free();
spin_lock();
t = timer->timer;
timer->timer = NULL;
spin_unlock();
hrtimer_cancel(&t->timer);
kfree(t);

/* UAF on t */
hrtimer_cancel(&t->timer);

In bpf_timer_cancel_and_free, this patch frees the timer->timer
after a rcu grace period. This requires a rcu_head addition
to the "struct bpf_hrtimer". Another kfree(t) happens in bpf_timer_init,
this does not need a kfree_rcu because it is still under the
spin_lock and timer->timer has not been visible by others yet.

In bpf_timer_cancel, rcu_read_lock() is added because this helper
can be used in a non rcu critical section context (e.g. from
a sleepable bpf prog). Other timer->timer usages in helpers.c
have been audited, bpf_timer_cancel() is the only place where
timer->timer is used outside of the spin_lock.

Another solution considered is to mark a t->flag in bpf_timer_cancel
and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free,
it busy waits for the flag to be cleared before kfree(t). This patch
goes with a straight forward solution and frees timer->timer after
a rcu grace period.
Published: 2024-04-03
Score: 5.5 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Debian DSA Debian DSA DSA-5658-1 linux security update
Ubuntu USN Ubuntu USN USN-6820-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6820-2 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-6821-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6821-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-6821-3 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-6821-4 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-6828-1 Linux kernel (Intel IoTG) vulnerabilities
Ubuntu USN Ubuntu USN USN-6871-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-6892-1 Linux kernel (IBM) vulnerabilities
Ubuntu USN Ubuntu USN USN-6919-1 Linux kernel vulnerabilities
History

Fri, 04 Apr 2025 15:00:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.8:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.8:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.8:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.8:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.8:rc5:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel

Wed, 07 Aug 2024 22:45:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:rhel_eus:9.2

Wed, 07 Aug 2024 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Redhat rhel Eus
CPEs cpe:/a:redhat:rhel_eus:9.2::nfv
Vendors & Products Redhat rhel Eus

Subscriptions

Linux Linux Kernel
Redhat Enterprise Linux Rhel Eus
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-11T20:03:10.783Z

Reserved: 2024-02-19T14:20:24.166Z

Link: CVE-2024-26737

cve-icon Vulnrichment

Updated: 2024-08-02T00:14:13.230Z

cve-icon NVD

Status : Analyzed

Published: 2024-04-03T17:15:51.243

Modified: 2025-04-04T14:34:28.903

Link: CVE-2024-26737

cve-icon Redhat

Severity : Moderate

Publid Date: 2024-04-03T00:00:00Z

Links: CVE-2024-26737 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses