hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB963V CVE: NA

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In nmi_trigger_cpumask_backtrace(), printk_safe_flush() is called after sending NMI to flush the logs. When logbuf_lock is already held and the current CPU is in printk-safe context (e.g., NMI context), attempting to acquire the lock again can lead to deadlock.

Modify the function to return early when detecting logbuf_lock is held and current CPU is in printk-safe context. This prevents deadlock scenarios where CPU0 holds the lock while other CPUs try to acquire it in NMI context.

Fixes: 099f1c84c005 ("printk: introduce per-cpu safe_print seq buffer") Signed-off-by: Xiaomeng Zhang zhangxiaomeng13@huawei.com --- kernel/printk/printk_safe.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index 809f92492ec7..c97845688fe1 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -256,6 +256,10 @@ void printk_safe_flush(void) { int cpu;

+ if (raw_spin_is_locked(&logbuf_lock) && + (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK)) + return; + for_each_possible_cpu(cpu) { #ifdef CONFIG_PRINTK_NMI __printk_safe_flush(&per_cpu(nmi_print_seq, cpu).work);