net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources()

In mlx4_en_try_alloc_resources(), mlx4_en_copy_priv() is called and
tmp->tx_cq will be freed on the error path of mlx4_en_copy_priv().
After that mlx4_en_alloc_resources() is called and there is a dereference
of &tmp->tx_cq[t][i] in mlx4_en_alloc_resources(), which could lead to
a use after free problem on failure of mlx4_en_copy_priv().

Fix this bug by adding a check of mlx4_en_copy_priv()

This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Builds with CONFIG_MLX4_EN=m show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 9d0750234dbf ("net/mlx4_en: Add resilience in low memory systems")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20211130164438.190591-1-zhou1615@umn.edu
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index 3f6d5c38463723e23be94af802bdf707f9a7c4e2..f1c10f2bda780a1d4a9dabe3c1a126b80809e5e9 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -2286,9 +2286,14 @@ int mlx4_en_try_alloc_resources(struct mlx4_en_priv *priv,
                                bool carry_xdp_prog)
 {
        struct bpf_prog *xdp_prog;
-       int i, t;
+       int i, t, ret;
 
-       mlx4_en_copy_priv(tmp, priv, prof);
+       ret = mlx4_en_copy_priv(tmp, priv, prof);
+       if (ret) {
+               en_warn(priv, "%s: mlx4_en_copy_priv() failed, return\n",
+                       __func__);
+               return ret;
+       }
 
        if (mlx4_en_alloc_resources(tmp)) {
                en_warn(priv,