Commit 92cf7a51 authored by Matthieu Baerts (NGI0)'s avatar Matthieu Baerts (NGI0) Committed by Jakub Kicinski
Browse files

mptcp: sysctl: blackhole timeout: avoid using current->nsproxy 

As mentioned in the previous commit, using the 'net' structure via
'current' is not recommended for different reasons:

- Inconsistency: getting info from the reader's/writer's netns vs only
  from the opener's netns.

- current->nsproxy can be NULL in some cases, resulting in an 'Oops'
  (null-ptr-deref), e.g. when the current task is exiting, as spotted by
  syzbot [1] using acct(2).

The 'pernet' structure can be obtained from the table->data using
container_of().

Fixes: 27069e7c ("mptcp: disable active MPTCP in case of blackhole")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@google.com

 [1]
Suggested-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Reviewed-by: default avatarMat Martineau <martineau@kernel.org>
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-3-5df34b2083e8@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent d38e26e3

net/mptcp/ctrl.c

+3 −1
Original line number Diff line number Diff line
@@ -160,7 +160,9 @@ static int proc_blackhole_detect_timeout(const struct ctl_table *table, 
					 int write, void *buffer, size_t *lenp,

					 loff_t *ppos)

{

	struct mptcp_pernet *pernet = mptcp_get_pernet(current->nsproxy->net_ns);

	struct mptcp_pernet *pernet = container_of(table->data,

						   struct mptcp_pernet,

						   blackhole_timeout);

	int ret;



	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);