Hi,
29.02.2024 02:51, Pablo Neira Ayuso wrote:
On Wed, Feb 28, 2024 at 02:47:03PM +0300, Alexander Ofitserov wrote:
The gtp_link_ops operations structure for the subsystem must be
registered after registering the gtp_net_ops pernet operations structure.
A fix for this was already applied, see:
commit 136cfaca22567a03bbb3bf53a43d8cb5748b80ec
Author: Vasiliy Kovalev <kovalev@xxxxxxxxxxxx>
Date: Wed Feb 14 19:27:33 2024 +0300
gtp: fix use-after-free and null-ptr-deref in gtp_genl_dump_pdp()
diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 2129ae42c7030..0ddec4cc84093 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1903,26 +1903,26 @@ static int __init gtp_init(void)
get_random_bytes(>p_h_initval, sizeof(gtp_h_initval));
- err = rtnl_link_register(>p_link_ops);
+ err = register_pernet_subsys(>p_net_ops);
if (err < 0)
goto error_out;
BTW, I like that this calls register_pernet_subsys() before
rtnl_link_register(), where a rtnetlink request could come before
pernet is set up.
- err = register_pernet_subsys(>p_net_ops);
+ err = rtnl_link_register(>p_link_ops);
if (err < 0)
- goto unreg_rtnl_link;
+ goto unreg_pernet_subsys;
err = genl_register_family(>p_genl_family);
if (err < 0)
- goto unreg_pernet_subsys;
+ goto unreg_rtnl_link;
pr_info("GTP module loaded (pdp ctx size %zd bytes)\n",
sizeof(struct pdp_ctx));
return 0;
-unreg_pernet_subsys:
- unregister_pernet_subsys(>p_net_ops);
unreg_rtnl_link:
rtnl_link_unregister(>p_link_ops);
+unreg_pernet_subsys:
+ unregister_pernet_subsys(>p_net_ops);
error_out:
pr_err("error loading GTP module loaded\n");
return err;
--
2.42.1
This patch fixes another problem, but a similar one, since the sequence
is incorrect when registering subsystems.
Initially, the registration sequence in the gtp module was as follows:
1) rtnl_link_register();
2) genl_register_family();
3) register_pernet_subsys();
During debugging of the module, when starting the syzkaller reproducer,
it turned out that after genl_register_family() (2),
without waiting for register_pernet_subsys()(3), the .dumpit event is
triggered, in which the data of the unregistered pernet subsystem is
accessed.
That is, the bug was fixed by the commit
136cfaca2256 ("gtp: fix use-after-free and null-ptr-deref in
gtp_genl_dump_pdp()") [1]
and the registration sequence became as follows:
1) rtnl_link_register();
2) register_pernet_subsys();
3) genl_register_family();
However, syzkaller has discovered another problem:
after registering rtnl_link_register, the .newlink event is triggered,
in which the data of the unregistered pernet subsystem is accessed.
This problem is reproducible on current stable kernels and the latest
upstream kernel 6.8-rc6, in which the patch 136cfaca2256 [1] is applied.
Therefore, the correct sequence should be as follows:
1) register_pernet_subsys();
2) rtnl_link_register();
3) genl_register_family();
The proposed patch is developed on top of the commit changes [1], does
not conflict with it and fixes the described bug.
[1]
https://lore.kernel.org/lkml/20240220160434.29bcaf43@xxxxxxxxxx/T/#mb1f72c2ad57b7ea6d47333e8616beccf8bce0e23
--
Regards,
Vasiliy Kovalev