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

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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: 27069e7cb3 ("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: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-3-5df34b2083e8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Matthieu Baerts (NGI0) 2025-01-08 16:34:31 +01:00 committed by Jakub Kicinski
parent d38e26e362
commit 92cf7a51bd
1 changed files with 3 additions and 1 deletions
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4
net/mptcp/ctrl.c
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@ -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);