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From:   Phil Elwell <phil@raspberrypi.com>
To:     Arend van Spriel <aspriel@gmail.com>,
        Chung-hsien Hsu <chung-hsien.hsu@infineon.com>,
        Kalle Valo <kvalo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Phil Elwell <phil@raspberrypi.com>,
        linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        SHA-cyfmac-dev-list@infineon.com
Subject: [PATCH] brcmfmac: firmware: Fix crash in brcm_alt_fw_path
Date:   Tue, 18 Jan 2022 15:45:14 +0000
Message-Id: <20220118154514.3245524-1-phil@raspberrypi.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The call to brcm_alt_fw_path in brcmf_fw_get_firmwares is not protected
by a check to the validity of the fwctx->req->board_type pointer. This
results in a crash in strlcat when, for example, the WLAN chip is found
in a USB dongle.

Prevent the crash by adding the necessary check.

See: https://github.com/raspberrypi/linux/issues/4833

Fixes: 5ff013914c62 ("brcmfmac: firmware: Allow per-board firmware binaries")
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c
index 0eb13e5df5177..d99140960a820 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c
@@ -693,7 +693,7 @@ int brcmf_fw_get_firmwares(struct device *dev, struct brcmf_fw_request *req,
 {
 	struct brcmf_fw_item *first = &req->items[0];
 	struct brcmf_fw *fwctx;
-	char *alt_path;
+	char *alt_path = NULL;
 	int ret;
 
 	brcmf_dbg(TRACE, "enter: dev=%s\n", dev_name(dev));
@@ -712,7 +712,9 @@ int brcmf_fw_get_firmwares(struct device *dev, struct brcmf_fw_request *req,
 	fwctx->done = fw_cb;
 
 	/* First try alternative board-specific path if any */
-	alt_path = brcm_alt_fw_path(first->path, fwctx->req->board_type);
+	if (fwctx->req->board_type)
+		alt_path = brcm_alt_fw_path(first->path,
+					    fwctx->req->board_type);
 	if (alt_path) {
 		ret = request_firmware_nowait(THIS_MODULE, true, alt_path,
 					      fwctx->dev, GFP_KERNEL, fwctx,
-- 
2.25.1