Fix a race where irq_work can be queued in bpf_ringbuf_commit() but the ring buffer is freed before the work executes. In the syzbot reproducer, a BPF program attached to sched_switch triggers bpf_ringbuf_commit(), queuing an irq_work. If the ring buffer is freed before this work executes, the irq_work thread may accesses freed memory. Calling `irq_work_sync(&rb->work)` ensures that all pending irq_work complete before freeing the buffer Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") Reported-by: syzbot+2617fc732430968b45d2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2617fc732430968b45d2 Tested-by: syzbot+2617fc732430968b45d2@syzkaller.appspotmail.com Signed-off-by: Noorain Eqbal --- v2: Updated the commit message for clarity. --- kernel/bpf/ringbuf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 719d73299397..d706c4b7f532 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -216,6 +216,8 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr) static void bpf_ringbuf_free(struct bpf_ringbuf *rb) { + irq_work_sync(&rb->work); + /* copy pages pointer and nr_pages to local variable, as we are going * to unmap rb itself with vunmap() below */ -- 2.51.0