Patch "ar5523: Fix null-ptr-deref with unexpected WDCMSG_TARGET_START reply" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ar5523: Fix null-ptr-deref with unexpected WDCMSG_TARGET_START reply

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ar5523-fix-null-ptr-deref-with-unexpected-wdcmsg_tar.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit dbaabd7796f97487f3849855abc43cf43652fd86
Author: Zekun Shen <bruceshenzk@xxxxxxxxx>
Date:   Thu Oct 28 18:37:49 2021 -0400

    ar5523: Fix null-ptr-deref with unexpected WDCMSG_TARGET_START reply
    
    [ 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>

diff --git a/drivers/net/wireless/ath/ar5523/ar5523.c b/drivers/net/wireless/ath/ar5523/ar5523.c
index 49cc4b7ed5163..1baec4b412c8d 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;