__vsock_net_mode_string() returns success without updating new_mode when
the transfer length is zero. Its caller then reads the uninitialized enum
and may permanently store a stack-derived value in the write-once child
mode.
Return before calling __vsock_net_mode_string() when *lenp is zero so
that the helper is never invoked with nothing to parse and new_mode is
never read uninitialized. This also prevents an empty write from
locking the current mode.
Fixes: eafb64f40ca4 ("vsock: add netns to vsock core")
Cc: [email protected]
Reviewed-by: Luigi Leonardi <[email protected]>
Signed-off-by: Aldo Ariel Panzardo <[email protected]>
---
Changes in v3:
- Move the !*lenp early return before __vsock_net_mode_string()
instead of after it, as suggested by Stefano Garzarella.
- Add missing maintainer CCs per get_maintainer.pl.
- Add Luigi's Reviewed-by.
Changes in v2:
- Return early instead of initializing new_mode to the current
value, which would silently consume the write-once transition.
net/vmw_vsock/af_vsock.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 622dbd0467..XXXXXXX 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -2879,6 +2879,9 @@ static int vsock_net_child_mode_string(const struct
ctl_table *table, int write,
net = container_of(table->data, struct net, vsock.child_ns_mode);
+ if (!*lenp)
+ return 0;
+
ret = __vsock_net_mode_string(table, write, buffer, lenp, ppos,
vsock_net_child_mode(net), &new_mode);
if (ret)
--
2.43.0
