6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/67769ecb.050a0220.3a8527.003f.GAE@xxxxxxxxxx [1]
Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Link: https://patch.msgid.link/20250108-net-sysctl-current-nsproxy-v1-4-5df34b2083e8@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sctp/sysctl.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -380,7 +380,8 @@ static struct ctl_table sctp_net_table[]
static int proc_sctp_do_hmac_alg(struct ctl_table *ctl, int write,
void *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";
