From f0813bcd2d9d97fdbdf2efb9532ab03ae92e99e6 Mon Sep 17 00:00:00 2001 From: Kery Qi Date: Fri, 23 Jan 2026 01:04:01 +0800 Subject: [PATCH] net: wwan: t7xx: fix potential skb->frags overflow in RX path When receiving data in the DPMAIF RX path, the t7xx_dpmaif_set_frag_to_skb() function adds page fragments to an skb without checking if the number of fragments has exceeded MAX_SKB_FRAGS. This could lead to a buffer overflow in skb_shinfo(skb)->frags[] array, corrupting adjacent memory and potentially causing kernel crashes or other undefined behavior. This issue was identified through static code analysis by comparing with a similar vulnerability fixed in the mt76 driver commit b102f0c522cf ("mt76: fix array overflow on receiving too many fragments for a packet"). The vulnerability could be triggered if the modem firmware sends packets with excessive fragments. While under normal protocol conditions (MTU 3080 bytes, BAT buffer 3584 bytes), a single packet should not require additional fragments, the kernel should not blindly trust firmware behavior. Malicious, buggy, or compromised firmware could potentially craft packets with more fragments than the kernel expects. Fix this by adding a bounds check before calling skb_add_rx_frag() to ensure nr_frags does not exceed MAX_SKB_FRAGS. The check must be performed before unmapping to avoid a page leak and double DMA unmap during device teardown. Fixes: d642b012df70a ("net: wwan: t7xx: Add data path interface") Signed-off-by: Kery Qi Link: https://patch.msgid.link/20260122170401.1986-2-qikeyu2017@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c index b76bea6ab2d76..5af90ca6e0631 100644 --- a/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c +++ b/drivers/net/wwan/t7xx/t7xx_hif_dpmaif_rx.c @@ -395,6 +395,7 @@ static int t7xx_dpmaif_set_frag_to_skb(const struct dpmaif_rx_queue *rxq, struct sk_buff *skb) { unsigned long long data_bus_addr, data_base_addr; + struct skb_shared_info *shinfo = skb_shinfo(skb); struct device *dev = rxq->dpmaif_ctrl->dev; struct dpmaif_bat_page *page_info; unsigned int data_len; @@ -402,18 +403,22 @@ static int t7xx_dpmaif_set_frag_to_skb(const struct dpmaif_rx_queue *rxq, page_info = rxq->bat_frag->bat_skb; page_info += t7xx_normal_pit_bid(pkt_info); - dma_unmap_page(dev, page_info->data_bus_addr, page_info->data_len, DMA_FROM_DEVICE); if (!page_info->page) return -EINVAL; + if (shinfo->nr_frags >= MAX_SKB_FRAGS) + return -EINVAL; + + dma_unmap_page(dev, page_info->data_bus_addr, page_info->data_len, DMA_FROM_DEVICE); + data_bus_addr = le32_to_cpu(pkt_info->pd.data_addr_h); data_bus_addr = (data_bus_addr << 32) + le32_to_cpu(pkt_info->pd.data_addr_l); data_base_addr = page_info->data_bus_addr; data_offset = data_bus_addr - data_base_addr; data_offset += page_info->offset; data_len = FIELD_GET(PD_PIT_DATA_LEN, le32_to_cpu(pkt_info->header)); - skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page_info->page, + skb_add_rx_frag(skb, shinfo->nr_frags, page_info->page, data_offset, data_len, page_info->data_len); page_info->page = NULL; -- 2.47.3