We found this bug while fuzzing the rsi_usb driver. rsi_prepare_skb does not check for OOB memcpy. We add the check in the caller to fix. Although rsi_prepare_skb checks if length is larger than (4 * RSI_RCV_BUFFER_LEN), it really can't because length is 0xfff maximum. So the check in patch is sufficient. This patch is created upon ath-next branch. It is NOT tested with real device, but with QEMU emulator. Following is the bug report BUG: KASAN: use-after-free in rsi_read_pkt (/linux/drivers/net/wireless/rsi/rsi_91x_main.c:206) rsi_91x Read of size 3815 at addr ffff888031da736d by task RX-Thread/204 CPU: 0 PID: 204 Comm: RX-Thread Not tainted 5.6.0 #5 Call Trace: dump_stack (/linux/lib/dump_stack.c:120) ? rsi_read_pkt (/linux/drivers/net/wireless/rsi/rsi_91x_main.c:206) rsi_91x print_address_description.constprop.6 (/linux/mm/kasan/report.c:377) ? rsi_read_pkt (/linux/drivers/net/wireless/rsi/rsi_91x_main.c:206) rsi_91x ? rsi_read_pkt (/linux/drivers/net/wireless/rsi/rsi_91x_main.c:206) rsi_91x __kasan_report.cold.9 (/linux/mm/kasan/report.c:510) ? syscall_return_via_sysret (/linux/arch/x86/entry/entry_64.S:253) ? rsi_read_pkt (/linux/drivers/net/wireless/rsi/rsi_91x_main.c:206) rsi_91x kasan_report (/linux/arch/x86/include/asm/smap.h:69 /linux/mm/kasan/common.c:644) check_memory_region (/linux/mm/kasan/generic.c:186 /linux/mm/kasan/generic.c:192) memcpy (/linux/mm/kasan/common.c:130) rsi_read_pkt (/linux/drivers/net/wireless/rsi/rsi_91x_main.c:206) rsi_91x ? skb_dequeue (/linux/net/core/skbuff.c:3042) rsi_usb_rx_thread (/linux/drivers/net/wireless/rsi/rsi_91x_usb_ops.c:47) rsi_usb Reported-by: Brendan Dolan-Gavitt <brendandg@xxxxxxx> Signed-off-by: Zekun Shen <bruceshenzk@xxxxxxxxx> --- drivers/net/wireless/rsi/rsi_91x_main.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/net/wireless/rsi/rsi_91x_main.c b/drivers/net/wireless/rsi/rsi_91x_main.c index 5d1490fc3..41d3c12e0 100644 --- a/drivers/net/wireless/rsi/rsi_91x_main.c +++ b/drivers/net/wireless/rsi/rsi_91x_main.c @@ -193,6 +193,10 @@ int rsi_read_pkt(struct rsi_common *common, u8 *rx_pkt, s32 rcv_pkt_len) break; case RSI_WIFI_DATA_Q: + if (!rcv_pkt_len && offset + length > + RSI_MAX_RX_USB_PKT_SIZE) + goto fail; + skb = rsi_prepare_skb(common, (frame_desc + offset), length, -- 2.25.1
