From: Zekun Shen <bruceshenzk@xxxxxxxxx> [ Upstream commit ae80b6033834342601e99f74f6a62ff5092b1cee ] Unexpected WDCMSG_TARGET_START replay can lead to null-ptr-deref when ar->tx_cmd->odata is NULL. The patch adds a null check to prevent such case. KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] ar5523_cmd+0x46a/0x581 [ar5523] ar5523_probe.cold+0x1b7/0x18da [ar5523] ? ar5523_cmd_rx_cb+0x7a0/0x7a0 [ar5523] ? __pm_runtime_set_status+0x54a/0x8f0 ? _raw_spin_trylock_bh+0x120/0x120 ? pm_runtime_barrier+0x220/0x220 ? __pm_runtime_resume+0xb1/0xf0 usb_probe_interface+0x25b/0x710 really_probe+0x209/0x5d0 driver_probe_device+0xc6/0x1b0 device_driver_attach+0xe2/0x120 I found the bug using a custome USBFuzz port. It's a research work to fuzz USB stack/drivers. I modified it to fuzz ath9k driver only, providing hand-crafted usb descriptors to QEMU. After fixing the code (fourth byte in usb packet) to WDCMSG_TARGET_START, I got the null-ptr-deref bug. I believe the bug is triggerable whenever cmd->odata is NULL. After patching, I tested with the same input and no longer see the KASAN report. This was NOT tested on a real device. Signed-off-by: Zekun Shen <bruceshenzk@xxxxxxxxx> Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/YXsmPQ3awHFLuAj2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/net/wireless/ath/ar5523/ar5523.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/net/wireless/ath/ar5523/ar5523.c b/drivers/net/wireless/ath/ar5523/ar5523.c index 0e9bad33fac85..141c1b5a7b1f3 100644 --- a/drivers/net/wireless/ath/ar5523/ar5523.c +++ b/drivers/net/wireless/ath/ar5523/ar5523.c @@ -153,6 +153,10 @@ static void ar5523_cmd_rx_cb(struct urb *urb) ar5523_err(ar, "Invalid reply to WDCMSG_TARGET_START"); return; } + if (!cmd->odata) { + ar5523_err(ar, "Unexpected WDCMSG_TARGET_START reply"); + return; + } memcpy(cmd->odata, hdr + 1, sizeof(u32)); cmd->olen = sizeof(u32); cmd->res = 0; -- 2.34.1
