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Subject[PATCH 5.4 156/320] ar5523: Fix null-ptr-deref with unexpected WDCMSG_TARGET_START reply
From: Zekun Shen <>

[ 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

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 <>
Signed-off-by: Kalle Valo <>
Signed-off-by: Sasha Levin <>
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 4c57e79e5779a..58e189ec672f9 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");
+ 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;

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