5.4-stable review patch. If anyone has any objections, please let me know.
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From: "Matthieu Baerts (NGI0)" matttbe@kernel.org
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: 3c68198e7511 ("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: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-4-5df34b2083... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Magali Lemes magali.lemes@canonical.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/sysctl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/net/sctp/sysctl.c +++ b/net/sctp/sysctl.c @@ -326,7 +326,8 @@ static int proc_sctp_do_hmac_alg(struct 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; bool changed = false; char *none = "none";