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Mon, 20 Apr 2026 15:22:47 -0700 (PDT) Message-ID: Date: Tue, 21 Apr 2026 01:22:46 +0300 Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] wifi: rtw88: fix OOB read from firmware RX descriptor exceeding DMA buffer To: Ping-Ke Shih , Tristan Madani Cc: Johannes Berg , "linux-wireless@vger.kernel.org" References: <20260415222440.1545959-1-tristmd@gmail.com> <090b3c83-e3d5-4c8d-bd46-aaff692de529@gmail.com> Content-Language: en-US From: Bitterblue Smith In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 20/04/2026 08:31, Ping-Ke Shih wrote: > Bitterblue Smith wrote: >> >> On 16/04/2026 01:24, Tristan Madani wrote: >>> From: Tristan Madani >>> >>> 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 >>> --- >>> Note: v2 resubmission -- original sent via Gmail had HTML rendering >>> issues. This version uses git send-email for plain-text formatting. >>> >>> Changes in v2: >>> - v2: clarify field widths and maximum new_len derivation in commit >>> message, per Ping-Ke Shih's feedback. >>> >>> 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 (new_len > RTK_PCI_RX_BUF_SIZE) { > > Since this is data (hot) path, I'd prefer 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; >>> >>> >> >> I'm working on a patch which will implement the same validation >> in rtw_rx_query_rx_desc(), along with two other checks. I got a >> report about too short packets from RTL8814AU, so USB devices >> can also benefit from checking pkt_len. It will make this patch >> redundant. > > Bitterblue, if you can take the change of this patch into your > patch, I'd skip this patch. Please let me know your thought. > No, I was mistaken. My patch doesn't do exactly the same thing as this patch. It just checks if pkt_len is more than 11454. This patch is also needed. Sorry for the noise. >> >> Well, kind of. Maybe RTK_PCI_RX_BUF_SIZE is too small? 11454 + 24 >> doesn't take into account the PHY info size. > > In rtw_pci_sync_rx_desc_device(), driver does > buf_desc->buf_size = cpu_to_le16(RTK_PCI_RX_BUF_SIZE); > > This is to tell hardware the size of RX DMA buffer. I think hardware > can't DMA data over this size. > Indeed, I don't think the hardware will write more than RTK_PCI_RX_BUF_SIZE bytes. But I wonder if some bytes won't be lost (or the entire packet?) if it ever receives a frame of 11454 bytes and wants to attach a PHY status? Then it would need a buffer of 11454 + 24 + 32 bytes. I don't know if this ever happens. > Ping-Ke >