Hey Wenwen, > Subject: [PATCH] iw_cxgb4: fix a missing-check bug > > In c4iw_flush_hw_cq, the next CQE is acquired through t4_next_hw_cqe(). In > t4_next_hw_cqe(), the CQE, i.e., 'cq->queue[cq->cidx]', is checked to see > whether it is valid through t4_valid_cqe(). If it is valid, the address of > the CQE is then saved to 'hw_cqe'. Later on, the CQE is copied to the local > memory in create_read_req_cqe(). The problem here is that the CQE is > actually in a DMA region allocated by dma_alloc_coherent() in create_cq(). > Given that the device also has the permission to access the DMA region, a > malicious device controlled by an attacker can modify the CQE in the DMA > region after the check in t4_next_hw_cqe() but before the copy in > create_read_req_cqe(). By doing so, the attacker can supply invalid CQE, > which can cause undefined behavior of the kernel and introduce potential > security risks. >
If the dma device is malicious, couldn't it just dma some incorrect CQE but still valid in the first place? I don't think this patch actually solves the issue, and it forces a copy of a 64B CQE in a critical data io path. So I must NACK this. Thanks, Steve.
