[PATCH] mlxsw: fix refcount leak in mlxsw_sp_vrs_lpm_tree_replace()

[PATCH] mlxsw: fix refcount leak in mlxsw_sp_vrs_lpm_tree_replace()

[Wentao Liang]

When mlxsw_sp_vrs_lpm_tree_replace() fails after replacing some VRs,
the error rollback loop does not correctly revert the preceding
replacements. The loop decrements the index but fails to update the
vr pointer, which still points to the VR that caused the failure. As
a result, the condition and the rollback call always operate on the
same VR, potentially calling mlxsw_sp_vr_lpm_tree_replace() multiple
times on it while never rolling back the earlier VRs. Those VRs
continue to hold a reference to new_tree acquired via
mlxsw_sp_lpm_tree_hold(), leaking the reference count of new_tree.

Fix by reinitializing vr inside the error loop with the updated index:

	vr = &mlxsw_sp->router->vrs[i];

so that the loop correctly iterates over all VRs that were actually
replaced.

Cc: stable@vger.kernel.org
Fixes: fc922bb0dd94 ("mlxsw: spectrum_router: Use one LPM tree for all virtual routers")
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
 drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
index 7bd87d0547d8..3d6fdbab05e0 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
@@ -1018,6 +1018,7 @@ static int mlxsw_sp_vrs_lpm_tree_replace(struct mlxsw_sp *mlxsw_sp,
 
 err_tree_replace:
 	for (i--; i >= 0; i--) {
+		vr = &mlxsw_sp->router->vrs[i];
 		if (!mlxsw_sp_vr_lpm_tree_should_replace(vr, proto, new_id))
 			continue;
 		mlxsw_sp_vr_lpm_tree_replace(mlxsw_sp,
-- 
2.34.1

Re: [PATCH] mlxsw: fix refcount leak in mlxsw_sp_vrs_lpm_tree_replace()

[Ido Schimmel]

Same comment as on the last patch regarding subject prefix

On Tue, Jun 09, 2026 at 08:47:30AM +0000, Wentao Liang wrote:
> When mlxsw_sp_vrs_lpm_tree_replace() fails after replacing some VRs,
> the error rollback loop does not correctly revert the preceding
> replacements. The loop decrements the index but fails to update the
> vr pointer, which still points to the VR that caused the failure. As
> a result, the condition and the rollback call always operate on the
> same VR, potentially calling mlxsw_sp_vr_lpm_tree_replace() multiple
> times on it while never rolling back the earlier VRs. Those VRs
> continue to hold a reference to new_tree acquired via
> mlxsw_sp_lpm_tree_hold(), leaking the reference count of new_tree.
> 
> Fix by reinitializing vr inside the error loop with the updated index:
> 
> 	vr = &mlxsw_sp->router->vrs[i];
> 
> so that the loop correctly iterates over all VRs that were actually
> replaced.
> 
> Cc: stable@vger.kernel.org
> Fixes: fc922bb0dd94 ("mlxsw: spectrum_router: Use one LPM tree for all virtual routers")
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

Re: [PATCH] mlxsw: fix refcount leak in mlxsw_sp_vrs_lpm_tree_replace()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue,  9 Jun 2026 08:47:30 +0000 you wrote:
> When mlxsw_sp_vrs_lpm_tree_replace() fails after replacing some VRs,
> the error rollback loop does not correctly revert the preceding
> replacements. The loop decrements the index but fails to update the
> vr pointer, which still points to the VR that caused the failure. As
> a result, the condition and the rollback call always operate on the
> same VR, potentially calling mlxsw_sp_vr_lpm_tree_replace() multiple
> times on it while never rolling back the earlier VRs. Those VRs
> continue to hold a reference to new_tree acquired via
> mlxsw_sp_lpm_tree_hold(), leaking the reference count of new_tree.
> 
> [...]

Here is the summary with links:
  - mlxsw: fix refcount leak in mlxsw_sp_vrs_lpm_tree_replace()
    https://git.kernel.org/netdev/net-next/c/21cf8dc478a4

You are awesome, thank you!
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