drop_monitor: replace spin_lock by raw_spin_lock

Summary

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): [<ffffffffb1df2b33>] _raw_spin_unlock_irqrestore+0x63/0x80 hardirqs last disabled at (139909): [<ffffffffb19bd03d>] trace_drop_common.constprop.0+0x26d/0x290 softirqs last enabled at (139892): [<ffffffffb07a1083>] __local_bh_enable_ip+0x103/0x170 softirqs last disabled at (139898): [<ffffffffb0909b33>] rcu_cpu_kthread+0x93/0x1f0 Preemption disabled at: [<ffffffffb1de786b>] 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: <TASK> 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.

Timeline

1. Jul 12, 2024, 12:32 PM UTCCVE published
2. Sep 10, 2024, 5:02 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Oct 15, 2026, 12:46 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in 594e47957f3fe034645e6885393ce96c12286334; From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in 96941f29ebcc1e9cbf570dc903f30374909562f5; From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in b3722fb69468693555f531cddda5c30444726dac; From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in f251ccef1d864790e5253386e95544420b7cd8f3; From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in 76ce2f9125244e1708d29c1d3f9d1d50b347bda0; From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in 07ea878684dfb78a9d4f564c39d07e855a9e242e; From 4ea7e38696c7e798c47ebbecadfd392f23f814f9 · fixed in f1e197a665c2148ebc25fe09c53689e60afea195

• Linux Linux

  2.6.31

• KernelLinux

  From 2.6.31 · fixed in 5.4.279; From 5.5.0 · fixed in 5.10.221; From 5.11.0 · fixed in 5.15.162; From 5.16.0 · fixed in 6.1.96; From 6.2.0 · fixed in 6.6.36; From 6.7.0 · fixed in 6.9.7

References 7