Subject: Re: [PATCH] brcmfmac: Fix a NULL pointer dereference in brcmf_of_probe()

From: Greg KH <[email-masked]>
Date: Fri, 28 Jan 2022 11:19:17 +0100

On Tue, Jan 25, 2022 at 12:50:46AM +0800, Zhou Qingyang wrote:
> 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 <[email-masked]>
> ---
> 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
> 

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