diff options
| author | Erni Sri Satya Vennela <ernis@linux.microsoft.com> | 2026-05-14 12:41:51 -0700 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2026-05-19 13:00:28 +0200 |
| commit | 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870 (patch) | |
| tree | bb99a197da32fa777d99376535c57d84bb9cc6dc /drivers/net/ethernet/microsoft | |
| parent | 2d85ae5d0f39c715277bcf0b4e65d2eed39c34bb (diff) | |
net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer
In mana_hwc_rx_event_handler(), resp->response.hwc_msg_id is read from
DMA-coherent memory and bounds-checked, then mana_hwc_handle_resp()
re-reads the same field from the same DMA buffer for test_bit() and
pointer arithmetic.
DMA-coherent memory is mapped uncacheable on x86 and is shared,
unencrypted, in Confidential VMs (SEV-SNP/TDX), so each load goes
directly to host-visible memory. A H/W can modify the value
between the check and the use, bypassing the bounds validation.
Fix this by reading hwc_msg_id exactly once using READ_ONCE() into a
stack-local variable in mana_hwc_rx_event_handler(), and passing the
validated value as a parameter to mana_hwc_handle_resp().
Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
Link: https://patch.msgid.link/20260514194156.466823-1-ernis@linux.microsoft.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'drivers/net/ethernet/microsoft')
| -rw-r--r-- | drivers/net/ethernet/microsoft/mana/hw_channel.c | 23 |
1 files changed, 13 insertions, 10 deletions
diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c b/drivers/net/ethernet/microsoft/mana/hw_channel.c index dbbde0fa57e7..fd8b324d7fb6 100644 --- a/drivers/net/ethernet/microsoft/mana/hw_channel.c +++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c @@ -77,21 +77,19 @@ static int mana_hwc_post_rx_wqe(const struct hwc_wq *hwc_rxq, } static void mana_hwc_handle_resp(struct hw_channel_context *hwc, u32 resp_len, - struct hwc_work_request *rx_req) + struct hwc_work_request *rx_req, u16 msg_id) { const struct gdma_resp_hdr *resp_msg = rx_req->buf_va; struct hwc_caller_ctx *ctx; int err; - if (!test_bit(resp_msg->response.hwc_msg_id, - hwc->inflight_msg_res.map)) { - dev_err(hwc->dev, "hwc_rx: invalid msg_id = %u\n", - resp_msg->response.hwc_msg_id); + if (!test_bit(msg_id, hwc->inflight_msg_res.map)) { + dev_err(hwc->dev, "hwc_rx: invalid msg_id = %u\n", msg_id); mana_hwc_post_rx_wqe(hwc->rxq, rx_req); return; } - ctx = hwc->caller_ctx + resp_msg->response.hwc_msg_id; + ctx = hwc->caller_ctx + msg_id; err = mana_hwc_verify_resp_msg(ctx, resp_msg, resp_len); if (err) goto out; @@ -251,6 +249,7 @@ static void mana_hwc_rx_event_handler(void *ctx, u32 gdma_rxq_id, struct gdma_sge *sge; u64 rq_base_addr; u64 rx_req_idx; + u16 msg_id; u8 *wqe; if (WARN_ON_ONCE(hwc_rxq->gdma_wq->id != gdma_rxq_id)) @@ -269,13 +268,17 @@ static void mana_hwc_rx_event_handler(void *ctx, u32 gdma_rxq_id, rx_req = &hwc_rxq->msg_buf->reqs[rx_req_idx]; resp = (struct gdma_resp_hdr *)rx_req->buf_va; - if (resp->response.hwc_msg_id >= hwc->num_inflight_msg) { - dev_err(hwc->dev, "HWC RX: wrong msg_id=%u\n", - resp->response.hwc_msg_id); + /* Read msg_id once from DMA buffer to prevent TOCTOU: + * DMA memory is shared/unencrypted in CVMs - host can + * modify it between reads. + */ + msg_id = READ_ONCE(resp->response.hwc_msg_id); + if (msg_id >= hwc->num_inflight_msg) { + dev_err(hwc->dev, "HWC RX: wrong msg_id=%u\n", msg_id); return; } - mana_hwc_handle_resp(hwc, rx_oob->tx_oob_data_size, rx_req); + mana_hwc_handle_resp(hwc, rx_oob->tx_oob_data_size, rx_req, msg_id); /* Can no longer use 'resp', because the buffer is posted to the HW * in mana_hwc_handle_resp() above. |