Attacker Value
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Privileges Required
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0

CVE-2024-26737

Disclosure Date: April 03, 2024 •
CVE-2024-26737
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

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.

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CVSS V3 Severity and Metrics
Base Score:
None
Impact Score:
Unknown
Exploitability Score:
Unknown
Vector:
Unknown
Attack Vector (AV):
Unknown
Attack Complexity (AC):
Unknown
Privileges Required (PR):
Unknown
User Interaction (UI):
Unknown
Scope (S):
Unknown
Confidentiality (C):
Unknown
Integrity (I):
Unknown
Availability (A):
Unknown

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
Linux 5268bb02107b
Linux not down converted
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • Linux

Products

  • Linux
Technical Analysis