6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Noorain Eqbal nooraineqbal@gmail.com
[ Upstream commit 4e9077638301816a7d73fa1e1b4c1db4a7e3b59c ]
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 nooraineqbal@gmail.com Link: https://lore.kernel.org/r/20251020180301.103366-1-nooraineqbal@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/ringbuf.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 6aff5ee483b60..c0c5e9b313e43 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -215,6 +215,8 @@ 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 */