From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Yael Chemla <ychemla@nvidia.com>,
	Dragos Tatulea <dtatulea@nvidia.com>,
	Tariq Toukan <tariqt@nvidia.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12 0690/1102] net/mlx5: E-Switch: fix use-after-free in mlx5_eswitch_termtbl_put
Date: Thu, 17 Sep 2026 16:10:33 +0100
Message-ID: <20260917151557.595248728@linuxfoundation.org>
In-Reply-To: <20260917151539.408551884@linuxfoundation.org>
References: <20260917151539.408551884@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yael Chemla <ychemla@nvidia.com>

[ Upstream commit 7ee07f601f8f507c9faf25c68a49396ab8950596 ]

In mlx5_eswitch_termtbl_put(), the zero-ref cleanup check reads
tt->ref_count after termtbl_mutex has been released.  Two concurrent
callers on the same mlx5_termtbl_handle race: one decrements ref_count
to zero, removes the hash entry, and calls kfree(tt) while the other
has already dropped the mutex and is about to evaluate
if (!tt->ref_count), producing a use-after-free.

Fix this by capturing the result of the decrement into a stack-local
last variable before dropping the mutex.  The cleanup decision is now
made entirely under termtbl_mutex, and tt is not touched after
kfree.

Fixes: 10caabdaad5a ("net/mlx5e: Use termination table for VLAN push actions")
Signed-off-by: Yael Chemla <ychemla@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260902193514.3668880-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 .../ethernet/mellanox/mlx5/core/eswitch_offloads_termtbl.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads_termtbl.c b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads_termtbl.c
index 40bdc677f051d..e282f65b8756a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads_termtbl.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads_termtbl.c
@@ -163,12 +163,15 @@ void
 mlx5_eswitch_termtbl_put(struct mlx5_eswitch *esw,
 			 struct mlx5_termtbl_handle *tt)
 {
+	bool last;
+
 	mutex_lock(&esw->offloads.termtbl_mutex);
-	if (--tt->ref_count == 0)
+	last = (--tt->ref_count == 0);
+	if (last)
 		hash_del(&tt->termtbl_hlist);
 	mutex_unlock(&esw->offloads.termtbl_mutex);
 
-	if (!tt->ref_count) {
+	if (last) {
 		mlx5_del_flow_rules(tt->rule);
 		mlx5_destroy_flow_table(tt->termtbl);
 		kfree(tt);
-- 
2.53.0