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From:   Zhou Qingyang <zhou1615@umn.edu>
To:     zhou1615@umn.edu
Cc:     kjlu@umn.edu, Arend van Spriel <aspriel@gmail.com>,
        Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>,
        Chi-hsien Lin <chi-hsien.lin@infineon.com>,
        Wright Feng <wright.feng@infineon.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>,
        Len Baker <len.baker@gmx.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Shawn Guo <shawn.guo@linaro.org>,
        Hans deGoede <hdegoede@redhat.com>,
        Matthias Brugger <mbrugger@suse.com>,
        linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        SHA-cyfmac-dev-list@infineon.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] brcmfmac: Fix a NULL pointer dereference in brcmf_of_probe()
Date:   Tue, 25 Jan 2022 00:50:46 +0800
Message-Id: <20220124165048.54677-1-zhou1615@umn.edu>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

In brcmf_of_probe(), the return value of devm_kzalloc() is assigned to
board_type and there is a dereference of it in strcpy() right after
that. devm_kzalloc() could return NULL on failure of allocation, which
could lead to NULL pointer dereference.

Fix this bug by adding a NULL check of board_type.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code

Fixes: 29e354ebeeec ("brcmfmac: Transform compatible string for FW loading")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
---
The analysis employs differential checking to identify inconsistent 
security operations (e.g., checks or kfrees) between two code paths 
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

 drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c
index 513c7e6421b2..535e8ddeab8d 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c
@@ -80,6 +80,8 @@ void brcmf_of_probe(struct device *dev, enum brcmf_bus_type bus_type,
 		/* get rid of '/' in the compatible string to be able to find the FW */
 		len = strlen(tmp) + 1;
 		board_type = devm_kzalloc(dev, len, GFP_KERNEL);
+		if (!board_type)
+			return;
 		strscpy(board_type, tmp, len);
 		for (i = 0; i < board_type[i]; i++) {
 			if (board_type[i] == '/')
-- 
2.25.1