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Jiayuan ChenandGreg Kroah-Hartman
2dc7936230
[ Upstream commit91840be8f7] 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:810979682c("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 Signed-off-by: Sasha Levin <sashal@kernel.org>