CVE-2024-40980

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

drop_monitor: replace spin_lock by raw_spin_lock

trace_drop_common() is called with preemption disabled, and it acquires a spin_lock. This is problematic for RT kernels because spin_locks are sleeping locks in this configuration, which causes the following splat:

BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 449, name: rcuc/47 preempt_count: 1, expected: 0 RCU nest depth: 2, expected: 2 5 locks held by rcuc/47/449: #0: ff1100086ec30a60 ((softirq_ctrl.lock)){+.+.}-{2:2}, at: __local_bh_disable_ip+0x105/0x210 #1: ffffffffb394a280 (rcu_read_lock){….}-{1:2}, at: rt_spin_lock+0xbf/0x130 #2: ffffffffb394a280 (rcu_read_lock){….}-{1:2}, at: __local_bh_disable_ip+0x11c/0x210 #3: ffffffffb394a160 (rcu_callback){….}-{0:0}, at: rcu_do_batch+0x360/0xc70 #4: ff1100086ee07520 (&data->lock){+.+.}-{2:2}, at: trace_drop_common.constprop.0+0xb5/0x290 irq event stamp: 139909 hardirqs last enabled at (139908): [] _raw_spin_unlock_irqrestore+0x63/0x80 hardirqs last disabled at (139909): [] trace_drop_common.constprop.0+0x26d/0x290 softirqs last enabled at (139892): [] __local_bh_enable_ip+0x103/0x170 softirqs last disabled at (139898): [] rcu_cpu_kthread+0x93/0x1f0 Preemption disabled at: [] rt_mutex_slowunlock+0xab/0x2e0 CPU: 47 PID: 449 Comm: rcuc/47 Not tainted 6.9.0-rc2-rt1+ #7 Hardware name: Dell Inc. PowerEdge R650/0Y2G81, BIOS 1.6.5 04/15/2022 Call Trace: dump_stack_lvl+0x8c/0xd0 dump_stack+0x14/0x20 __might_resched+0x21e/0x2f0 rt_spin_lock+0x5e/0x130 ? trace_drop_common.constprop.0+0xb5/0x290 ? skb_queue_purge_reason.part.0+0x1bf/0x230 trace_drop_common.constprop.0+0xb5/0x290 ? preempt_count_sub+0x1c/0xd0 ? _raw_spin_unlock_irqrestore+0x4a/0x80 ? __pfx_trace_drop_common.constprop.0+0x10/0x10 ? rt_mutex_slowunlock+0x26a/0x2e0 ? skb_queue_purge_reason.part.0+0x1bf/0x230 ? __pfx_rt_mutex_slowunlock+0x10/0x10 ? skb_queue_purge_reason.part.0+0x1bf/0x230 trace_kfree_skb_hit+0x15/0x20 trace_kfree_skb+0xe9/0x150 kfree_skb_reason+0x7b/0x110 skb_queue_purge_reason.part.0+0x1bf/0x230 ? __pfx_skb_queue_purge_reason.part.0+0x10/0x10 ? mark_lock.part.0+0x8a/0x520 …

trace_drop_common() also disables interrupts, but this is a minor issue because we could easily replace it with a local_lock.

Replace the spin_lock with raw_spin_lock to avoid sleeping in atomic context.

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/07ea878684dfb78a9d4f564c39d07e855a9e242e
• https://git.kernel.org/stable/c/594e47957f3fe034645e6885393ce96c12286334
• https://git.kernel.org/stable/c/76ce2f9125244e1708d29c1d3f9d1d50b347bda0
• https://git.kernel.org/stable/c/96941f29ebcc1e9cbf570dc903f30374909562f5
• https://git.kernel.org/stable/c/b3722fb69468693555f531cddda5c30444726dac
• https://git.kernel.org/stable/c/f1e197a665c2148ebc25fe09c53689e60afea195
• https://git.kernel.org/stable/c/f251ccef1d864790e5253386e95544420b7cd8f3
• https://git.kernel.org/stable/c/07ea878684dfb78a9d4f564c39d07e855a9e242e
• https://git.kernel.org/stable/c/594e47957f3fe034645e6885393ce96c12286334
• https://git.kernel.org/stable/c/76ce2f9125244e1708d29c1d3f9d1d50b347bda0
• https://git.kernel.org/stable/c/96941f29ebcc1e9cbf570dc903f30374909562f5
• https://git.kernel.org/stable/c/b3722fb69468693555f531cddda5c30444726dac
• https://git.kernel.org/stable/c/f1e197a665c2148ebc25fe09c53689e60afea195
• https://git.kernel.org/stable/c/f251ccef1d864790e5253386e95544420b7cd8f3
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html