linux-kernel - Re: [PATCH] Prevent out-of-bounds read/write in bcmasp_netfilt_rd and bcmasp_netfilt

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Message-ID: <DB3PR10MB6835D962C88C7E862CBDE659E8A5A@DB3PR10MB6835.EURPRD10.PROD.OUTLOOK.COM>
Date:   Fri,  3 Nov 2023 19:44:05 +0530
From:   Yuran Pereira <yuran.pereira@...mail.com>
To:     gregkh@...uxfoundation.org, yuran.pereira@...mail.com
Cc:     bcm-kernel-feedback-list@...adcom.com, davem@...emloft.net,
        edumazet@...gle.com, florian.fainelli@...adcom.com,
        justin.chen@...adcom.com, kuba@...nel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        pabeni@...hat.com
Subject: Re: [PATCH] Prevent out-of-bounds read/write in bcmasp_netfilt_rd and bcmasp_netfilt_wr

I guess that explains why the first check returns 0.

```
static int bcmasp_netfilt_wr_m_wake(struct bcmasp_priv *priv,
...
{
		...
        if (first_byte && (!IS_ALIGNED(offset, 4) || size < 3)) {
            match_val = bcmasp_netfilt_rd(priv, nfilt,
                              ASP_NETFILT_MATCH,
                              ALIGN_DOWN(offset, 4));
            mask_val = bcmasp_netfilt_rd(priv, nfilt,
                             ASP_NETFILT_MASK,
                             ALIGN_DOWN(offset, 4));
        }

        shift = (3 - (offset % 4)) * 8;
        match_val &= ~GENMASK(shift + 7, shift);
        mask_val &= ~GENMASK(shift + 7, shift);
        match_val |= (u32)(*((u8 *)match) << shift);
        mask_val |= (u32)(*((u8 *)mask) << shift);

```