linux-kernel - [PATCH][next] octeontx2-af: Fix access of iter->entry after iter object has been kfree'd

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Date:   Wed, 18 Nov 2020 14:38:03 +0000
From:   Colin King <colin.king@...onical.com>
To:     Sunil Goutham <sgoutham@...vell.com>,
        Linu Cherian <lcherian@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Jerin Jacob <jerinj@...vell.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Naveen Mamindlapalli <naveenm@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] octeontx2-af: Fix access of iter->entry after iter object has been kfree'd

From: Colin Ian King <colin.king@...onical.com>

The call to pc_delete_flow can kfree the iter object, so the following
dev_err message that accesses iter->entry can accessmemory that has
just been kfree'd.  Fix this by adding a temporary variable 'entry'
that has a copy of iter->entry and also use this when indexing into
the array mcam->entry2target_pffunc[]. Also print the unsigned value
using the %u format specifier rather than %d.

Addresses-Coverity: ("Read from pointer after free")
Fixes: 55307fcb9258 ("octeontx2-af: Add mbox messages to install and delete MCAM rules")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/infiniband/hw/mlx5/mem.c                       | 2 +-
 drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
index 4ddfdff33a61..14832b66d1fe 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
@@ -1218,11 +1218,13 @@ int rvu_mbox_handler_npc_delete_flow(struct rvu *rvu,
 	mutex_unlock(&mcam->lock);
 
 	list_for_each_entry_safe(iter, tmp, &del_list, list) {
+		u16 entry = iter->entry;
+
 		/* clear the mcam entry target pcifunc */
-		mcam->entry2target_pffunc[iter->entry] = 0x0;
+		mcam->entry2target_pffunc[entry] = 0x0;
 		if (npc_delete_flow(rvu, iter, pcifunc))
-			dev_err(rvu->dev, "rule deletion failed for entry:%d",
-				iter->entry);
+			dev_err(rvu->dev, "rule deletion failed for entry:%u",
+				entry);
 	}
 
 	return 0;
-- 
2.28.0