From 31550d585589fde1ae95bf7f7a8188b2d2fdf1c7 Mon Sep 17 00:00:00 2001 From: Guanglei Zhu Date: Fri, 11 Sep 2026 10:17:33 +0800 Subject: [PATCH] net: wwan: mhi_wwan_mbim: check skb_copy_bits() return value mhi_mbim_rx() ignores the return value of skb_copy_bits() when it copies each datagram out of the NTB. The datagram offset and length come from the DPE, which is only checked to lie within the NTB itself, so a modem can point a datagram outside the received skb. The copy then fails and the freshly allocated skbn is passed to netif_rx() with its uninitialized contents still in place, leaking kernel heap memory into the network stack. Free the skb and account an error when the copy fails. Fixes: aa730a9905b7 ("net: wwan: Add MHI MBIM network driver") Cc: stable@vger.kernel.org Suggested-by: Loic Poulain Signed-off-by: Guanglei Zhu Verified in a QEMU guest with a fault injector pointing a DPE outside the received NTB: the copy fails, and the unpatched driver hands the uninitialized skbn to the network stack (observed as "unknown protocol" on bytes that were never written). With this check the failed datagram is dropped and counted as an rx error. Changes in v2: factor the free-and-count sequence out into mhi_mbim_rx_drop(), shared with the unknown-protocol path, as suggested by Loic Poulain. Link: https://patch.msgid.link/20260911021734.1396599-2-zhugl3@xiaopeng.com Signed-off-by: Jakub Kicinski --- drivers/net/wwan/mhi_wwan_mbim.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/net/wwan/mhi_wwan_mbim.c b/drivers/net/wwan/mhi_wwan_mbim.c index 5679948546a5..336f89756f10 100644 --- a/drivers/net/wwan/mhi_wwan_mbim.c +++ b/drivers/net/wwan/mhi_wwan_mbim.c @@ -251,6 +251,14 @@ static int mbim_rx_verify_ndp16(struct sk_buff *skb, struct usb_cdc_ncm_ndp16 *n return ret; } +static void mhi_mbim_rx_drop(struct mhi_mbim_link *link, struct sk_buff *skb) +{ + dev_kfree_skb_any(skb); + u64_stats_update_begin(&link->rx_syncp); + u64_stats_inc(&link->rx_errors); + u64_stats_update_end(&link->rx_syncp); +} + static void mhi_mbim_rx(struct mhi_mbim_context *mbim, struct sk_buff *skb) { int ndpoffset; @@ -320,7 +328,10 @@ static void mhi_mbim_rx(struct mhi_mbim_context *mbim, struct sk_buff *skb) continue; skb_put(skbn, dgram_len); - skb_copy_bits(skb, dgram_offset, skbn->data, dgram_len); + if (skb_copy_bits(skb, dgram_offset, skbn->data, dgram_len)) { + mhi_mbim_rx_drop(link, skbn); + continue; + } switch (skbn->data[0] & 0xf0) { case 0x40: @@ -332,10 +343,7 @@ static void mhi_mbim_rx(struct mhi_mbim_context *mbim, struct sk_buff *skb) default: net_err_ratelimited("%s: unknown protocol\n", link->ndev->name); - dev_kfree_skb_any(skbn); - u64_stats_update_begin(&link->rx_syncp); - u64_stats_inc(&link->rx_errors); - u64_stats_update_end(&link->rx_syncp); + mhi_mbim_rx_drop(link, skbn); continue; }