From ae80b6033834342601e99f74f6a62ff5092b1cee Mon Sep 17 00:00:00 2001
From: Zekun Shen <bruceshenzk@gmail.com>
Date: Thu, 28 Oct 2021 18:37:49 -0400
Subject: [PATCH] ar5523: Fix null-ptr-deref with unexpected WDCMSG_TARGET_START reply
Git-commit: ae80b6033834342601e99f74f6a62ff5092b1cee
Patch-mainline: v5.17-rc1
References: git-fixes

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@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/YXsmPQ3awHFLuAj2@10-18-43-117.dynapool.wireless.nyu.edu
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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 0e9bad33fac8..141c1b5a7b1f 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;
-- 
2.31.1