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Commit 1031462a authored by Matthieu Baerts (NGI0)'s avatar Matthieu Baerts (NGI0) Committed by Greg Kroah-Hartman
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sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy 

commit ea62dd1383913b5999f3d16ae99d411f41b528d4 upstream.

As mentioned in a previous commit of this series, 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 'net' structure can be obtained from the table->data using
container_of().

Note that table->data could also be used directly, as this is the only
member needed from the 'net' structure, but that would increase the size
of this fix, to use '*data' everywhere 'net->sctp.sctp_hmac_alg' is
used.

Fixes: 3c68198e ("sctp: Make hmac algorithm selection for cookie generation dynamic")
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>
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-4-5df34b2083e8@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ec037fe8

net/sctp/sysctl.c

+2 −1
Original line number Diff line number Diff line
@@ -441,7 +441,8 @@ static int proc_sctp_do_auth(struct ctl_table *ctl, int write, 
			     void __user *buffer, size_t *lenp,

			     loff_t *ppos)

{

	struct net *net = current->nsproxy->net_ns;

	struct net *net = container_of(ctl->data, struct net,

				       sctp.sctp_hmac_alg);

	struct ctl_table tbl;

	int new_value, ret;