[PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[Tristan Madani]

On Mon, 21 Apr 2026, Ping-Ke Shih wrote:
> Since this is data (hot) path, I'd prefer unlikely(new_len > RTK_PCI_RX_BUF_SIZE).

Good point. v3 below adds unlikely().

Thanks Bitterblue for clarifying -- glad the patches are complementary.

---

From: Tristan Madani <tristan@talencesecurity.com>
Subject: [PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

In rtw_pci_rx_napi(), new_len is computed as the sum of pkt_len (14-bit
descriptor field, max 16383) and pkt_offset (drv_info_sz + shift, both
firmware-controlled). The result can exceed RTK_PCI_RX_BUF_SIZE (11478),
causing an out-of-bounds read from the pre-allocated DMA buffer when
skb_put_data copies new_len bytes. The USB transport already validates
this (rtw_usb_rx_data_put checks against RTW_USB_MAX_RECVBUF_SZ); the
PCIe path does not.

Add a check that new_len does not exceed the DMA buffer size.

Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Changes in v3:
  - Wrap check in unlikely() since this is the RX hot path, per
    Ping-Ke Shih.

Changes in v2:
  - Clarify field widths and maximum new_len derivation in commit
    message, per Ping-Ke Shih.

 drivers/net/wireless/realtek/rtw88/pci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -1078,6 +1078,11 @@ static int rtw_pci_rx_napi(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
 		new_len = pkt_stat.pkt_len + pkt_offset;
+		if (unlikely(new_len > RTK_PCI_RX_BUF_SIZE)) {
+			rtw_dbg(rtwdev, RTW_DBG_RX,
+				"oversized RX packet: %u\n", new_len);
+			goto next_rp;
+		}
 		new = dev_alloc_skb(new_len);
 		if (WARN_ONCE(!new, "rx routine starvation\n"))
 			goto next_rp;
--
2.43.0

Re: [PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[Johannes Berg]

On Tue, 2026-04-21 at 10:35 +0000, Tristan Madani wrote:
> On Mon, 21 Apr 2026, Ping-Ke Shih wrote:
> > Since this is data (hot) path, I'd prefer unlikely(new_len > RTK_PCI_RX_BUF_SIZE).
> 
> Good point. v3 below adds unlikely().
> 
> Thanks Bitterblue for clarifying -- glad the patches are complementary.
> 
> ---
> 
> From: Tristan Madani <tristan@talencesecurity.com>
> Subject: [PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer
> 

This format doesn't work, you can't have a "preamble" section before a
"---" separator, only a "footer" section _after_ a "---" separator
(which doesn't go into the git history log.)

johannes

[PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[Tristan Madani]

From: Tristan Madani <tristan@talencesecurity.com>

In rtw_pci_rx_napi(), new_len is computed as the sum of pkt_len (14-bit
descriptor field, max 16383) and pkt_offset (drv_info_sz + shift, both
firmware-controlled). The result can exceed RTK_PCI_RX_BUF_SIZE (11478),
causing an out-of-bounds read from the pre-allocated DMA buffer when
skb_put_data copies new_len bytes. The USB transport already validates
this (rtw_usb_rx_data_put checks against RTW_USB_MAX_RECVBUF_SZ); the
PCIe path does not.

Add a check that new_len does not exceed the DMA buffer size.

Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Changes in v3:
  - Wrap check in unlikely() since this is the RX hot path, per
    Ping-Ke Shih.

Changes in v2:
  - Clarify field widths and maximum new_len derivation in commit
    message, per Ping-Ke Shih.

 drivers/net/wireless/realtek/rtw88/pci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
index XXXXXXX..XXXXXXX 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -1078,6 +1078,11 @@ static int rtw_pci_rx_napi(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
 		new_len = pkt_stat.pkt_len + pkt_offset;
+		if (unlikely(new_len > RTK_PCI_RX_BUF_SIZE)) {
+			rtw_dbg(rtwdev, RTW_DBG_RX,
+				"oversized RX packet: %u\n", new_len);
+			goto next_rp;
+		}
 		new = dev_alloc_skb(new_len);
 		if (WARN_ONCE(!new, "rx routine starvation\n"))
 			goto next_rp;
-- 
2.47.3

[PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[Tristan Madani]

From: Tristan Madani <tristan@talencesecurity.com>

In rtw_pci_rx_napi(), new_len is computed as the sum of pkt_len (14-bit
descriptor field, max 16383) and pkt_offset (drv_info_sz + shift, both
firmware-controlled). The result can exceed RTK_PCI_RX_BUF_SIZE (11478),
causing an out-of-bounds read from the pre-allocated DMA buffer when
skb_put_data copies new_len bytes. The USB transport already validates
this (rtw_usb_rx_data_put checks against RTW_USB_MAX_RECVBUF_SZ); the
PCIe path does not.

Add a check that new_len does not exceed the DMA buffer size.

Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
Changes in v3:
  - Wrap check in unlikely() since this is the RX hot path, per
    Ping-Ke Shih.

Changes in v2:
  - Clarify field widths and maximum new_len derivation in commit
    message, per Ping-Ke Shih.
 drivers/net/wireless/realtek/rtw88/pci.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
index bba370ad510cf..465598d5dc467 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -1077,6 +1077,11 @@ static u32 rtw_pci_rx_napi(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
 		 * discard the frame if none available
 		 */
 		new_len = pkt_stat.pkt_len + pkt_offset;
+		if (unlikely(new_len > RTK_PCI_RX_BUF_SIZE)) {
+			rtw_dbg(rtwdev, RTW_DBG_RX,
+				"oversized RX packet: %u\n", new_len);
+			goto next_rp;
+		}
 		new = dev_alloc_skb(new_len);
 		if (WARN_ONCE(!new, "rx routine starvation\n"))
 			goto next_rp;
-- 
2.47.3

Re: [PATCH v3] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

[Ping-Ke Shih]

Tristan Madani <tristmd@gmail.com> wrote:

> From: Tristan Madani <tristan@talencesecurity.com>
> 
> In rtw_pci_rx_napi(), new_len is computed as the sum of pkt_len (14-bit
> descriptor field, max 16383) and pkt_offset (drv_info_sz + shift, both
> firmware-controlled). The result can exceed RTK_PCI_RX_BUF_SIZE (11478),
> causing an out-of-bounds read from the pre-allocated DMA buffer when
> skb_put_data copies new_len bytes. The USB transport already validates
> this (rtw_usb_rx_data_put checks against RTW_USB_MAX_RECVBUF_SZ); the
> PCIe path does not.
> 
> Add a check that new_len does not exceed the DMA buffer size.
> 
> Fixes: e3037485c68e ("rtw88: new Realtek 802.11ac driver")
> Signed-off-by: Tristan Madani <tristan@talencesecurity.com>

1 patch(es) applied to rtw-next branch of rtw.git, thanks.

6e76e9ed273d wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer

---
https://github.com/pkshih/rtw.git