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| author | Jiayuan Chen <jiayuan.chen@linux.dev> | 2026-03-30 15:32:29 +0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@kernel.org> | 2026-05-11 16:28:04 +0200 |
| commit | 91840be8f710370607f949a627e070896faeddb8 (patch) | |
| tree | 512f0094678953b164c94ab48efe1115d414ec04 /kernel | |
| parent | cefafbd561402b0fe6447449364a30315b9b1570 (diff) | |
| download | linux-91840be8f710370607f949a627e070896faeddb8.tar.gz linux-91840be8f710370607f949a627e070896faeddb8.zip | |
irq_work: Fix use-after-free in irq_work_single() on PREEMPT_RT
On PREEMPT_RT, non-HARD irq_work runs in per-CPU kthreads via
run_irq_workd(), so irq_work_sync() uses rcuwait() to wait for BUSY==0.
After irq_work_single() clears BUSY via atomic_cmpxchg(), it still
dereferences @work for irq_work_is_hard() and rcuwait_wake_up().
An irq_work_sync() caller on another CPU that enters after BUSY is cleared
can observe BUSY==0 immediately, return, and free the work before those
accesses complete — causing a use-after-free.
Fix this by wrapping run_irq_workd() in guard(rcu)() so that the entire
irq_work_single() execution is within an RCU read-side critical
section. Then add synchronize_rcu() in irq_work_sync() after
rcuwait_wait_event() to ensure the caller waits for the RCU grace period
before returning, preventing premature frees.
Fixes: 810979682ccc ("irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.")
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20260330073234.303732-1-jiayuan.chen@linux.dev
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/irq_work.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/irq_work.c b/kernel/irq_work.c index 120fd7365fbe..f7e2dc2c30c6 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -292,6 +292,12 @@ void irq_work_sync(struct irq_work *work) !arch_irq_work_has_interrupt()) { rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work), TASK_UNINTERRUPTIBLE); + /* + * Ensure irq_work_single() does not access @work + * after removing IRQ_WORK_BUSY. It is always + * accessed within a RCU-read section. + */ + synchronize_rcu(); return; } @@ -302,6 +308,7 @@ EXPORT_SYMBOL_GPL(irq_work_sync); static void run_irq_workd(unsigned int cpu) { + guard(rcu)(); irq_work_run_list(this_cpu_ptr(&lazy_list)); } |