sched: address a potential NULL pointer dereference in the GRED scheduler.

[ Upstream commit 115ef44a98220fddfab37a39a19370497cd718b9 ]

If kzalloc in gred_init returns a NULL pointer, the code follows the
error handling path, invoking gred_destroy. This, in turn, calls
gred_offload, where memset could receive a NULL pointer as input,
potentially leading to a kernel crash.

When table->opt is NULL in gred_init(), gred_change_table_def()
is not called yet, so it is not necessary to call ->ndo_setup_tc()
in gred_offload().

Signed-off-by: Jun Yang <juny24602@gmail.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Fixes: f25c0515c521 ("net: sched: gred: dynamically allocate tc_gred_qopt_offload")
Link: https://patch.msgid.link/20250305154410.3505642-1-juny24602@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index 79ba9dc702541e95b9df2eee9ed6fe048b4330b2..43b0343a7cd0ca0bb7a8a8c0687ab333ae7716a0 100644 (file)
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -913,7 +913,8 @@ static void gred_destroy(struct Qdisc *sch)
        for (i = 0; i < table->DPs; i++)
                gred_destroy_vq(table->tab[i]);
 
-       gred_offload(sch, TC_GRED_DESTROY);
+       if (table->opt)
+               gred_offload(sch, TC_GRED_DESTROY);
        kfree(table->opt);
 }