CVE-2024-49926 rcu-tasks: Fix access non-existent percpu rtpcp variable in rcu_tasks_need_gpcb()
A null pointer dereference in the Linux kernel's RCU tasks subsystem causes a system panic when CONFIG_FORCE_NR_CPUS is enabled.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-49926?
CVE-2024-49926 is a medium-severity vulnerability in Linux kernel, published on 21 Oct 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
rcu-tasks: Fix access non-existent percpu rtpcp variable in rcu_tasks_need_gpcb()
For kernels built with CONFIG_FORCE_NR_CPUS=y, the nr_cpu_ids is defined as NR_CPUS instead of the number of possible cpus, this will cause the following system panic:
smpboot: Allowing 4 CPUs, 0 hotplug CPUs ... setup_percpu: NR_CPUS:512 nr_cpumask_bits:512 nr_cpu_ids:512 nr_node_ids:1 ... BUG: unable to handle page fault for address: ffffffff9911c8c8 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 15 Comm: rcu_tasks_trace Tainted: G W 6.6.21 #1 5dc7acf91a5e8e9ac9dcfc35bee0245691283ea6 RIP: 0010:rcu_tasks_need_gpcb+0x25d/0x2c0 RSP: 0018:ffffa371c00a3e60 EFLAGS: 00010082 CR2: ffffffff9911c8c8 CR3: 000000040fa20005 CR4: 00000000001706f0 Call Trace: <TASK> ? __die+0x23/0x80 ? page_fault_oops+0xa4/0x180 ? exc_page_fault+0x152/0x180 ? asm_exc_page_fault+0x26/0x40 ? rcu_tasks_need_gpcb+0x25d/0x2c0 ? __pfx_rcu_tasks_kthread+0x40/0x40 rcu_tasks_one_gp+0x69/0x180 rcu_tasks_kthread+0x94/0xc0 kthread+0xe8/0x140 ? __pfx_kthread+0x40/0x40 ret_from_fork+0x34/0x80 ? __pfx_kthread+0x40/0x40 ret_from_fork_asm+0x1b/0x80 </TASK>
Considering that there may be holes in the CPU numbers, use the maximum possible cpu number, instead of nr_cpu_ids, for configuring enqueue and dequeue limits.
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Which versions are affected by CVE-2024-49926?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-49926?
Apply the vendor's patch.
Is CVE-2024-49926 being exploited?
There is no known exploitation of CVE-2024-49926 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-52896, AZL-52959, BELL-CVE-2024-49926, DEBIAN-CVE-2024-49926, GHSA-2gvh-vj62-qjmp, ROOT-OS-DEBIAN-11-CVE-2024-49926 and 3 more.