linux-hardening - [PATCH][next] octeontx2-pf: Fix out-of-bounds read in otx2_get

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Date:   Fri, 12 Feb 2021 06:23:10 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Sunil Goutham <sgoutham@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        hariprasad <hkelam@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Christina Jacob <cjacob@...vell.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] octeontx2-pf: Fix out-of-bounds read in
 otx2_get_fecparam()

Code at line 967 implies that rsp->fwdata.supported_fec may be up to 4:

 967: if (rsp->fwdata.supported_fec <= FEC_MAX_INDEX)

If rsp->fwdata.supported_fec evaluates to 4, then there is an
out-of-bounds read at line 971 because fec is an array with
a maximum of 4 elements:

 954         const int fec[] = {
 955                 ETHTOOL_FEC_OFF,
 956                 ETHTOOL_FEC_BASER,
 957                 ETHTOOL_FEC_RS,
 958                 ETHTOOL_FEC_BASER | ETHTOOL_FEC_RS};
 959 #define FEC_MAX_INDEX 4

 971: fecparam->fec = fec[rsp->fwdata.supported_fec];

Fix this by properly indexing fec[] with rsp->fwdata.supported_fec - 1.
In this case the proper indexes 0 to 3 are used when
rsp->fwdata.supported_fec evaluates to a range of 1 to 4, correspondingly.

Fixes: d0cf9503e908 ("octeontx2-pf: ethtool fec mode support")
Addresses-Coverity-ID: 1501722 ("Out-of-bounds read")
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
index 237e5d3321d4..f7e8ada32a26 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
@@ -968,7 +968,7 @@ static int otx2_get_fecparam(struct net_device *netdev,
 		if (!rsp->fwdata.supported_fec)
 			fecparam->fec = ETHTOOL_FEC_NONE;
 		else
-			fecparam->fec = fec[rsp->fwdata.supported_fec];
+			fecparam->fec = fec[rsp->fwdata.supported_fec - 1];
 	}
 	return 0;
 }
-- 
2.27.0