On 12/13/2024 6:46 PM, Stephen Smalley wrote:
On Fri, Dec 13, 2024 at 5:57 AM Mikhail Ivanov
<ivanov.mikhail1@xxxxxxxxxxxxxxxxxxx> wrote:
On 12/12/2024 8:50 PM, Mickaël Salaün wrote:
This looks good be there are other places using sk->sk_family that
should also be fixed.
Thanks for checking this!
For selinux this should be enough, I haven't found any other places
where sk->sk_family could be read from an IPv6 socket without locking.
I also would like to prepare such fix for other LSMs (apparmor, smack,
tomoyo) (in separate patches).
I'm wondering about the implications for SELinux beyond just
sk->sk_family access, e.g. SELinux maps the (family, type, protocol)
triple to a security class at socket creation time via
socket_type_to_security_class() and caches the security class in the
inode_security_struct and sk_security_struct for later use.
IPv6 and IPv4 TCP sockets are mapped to the same SECCLASS_TCP_SOCKET
security class. AFAICS there is no other places that can be affected by
the IPV6_ADDFORM transformation.
On Thu, Dec 12, 2024 at 06:20:00PM +0800, Mikhail Ivanov wrote:
selinux_socket_bind() is called without holding the socket lock.
Use READ_ONCE() to safely read sk->sk_family for IPv6 socket in case
of lockless transformation to IPv4 socket via IPV6_ADDRFORM [1].
[1] https://lore.kernel.org/all/20240202095404.183274-1-edumazet@xxxxxxxxxx/
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@xxxxxxxxxxxxxxxxxxx>
---
security/selinux/hooks.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5e5f3398f39d..b7adff2cf5f6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4715,8 +4715,10 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
if (err)
goto out;
+ /* IPV6_ADDRFORM can change sk->sk_family under us. */
+ family = READ_ONCE(sk->sk_family);
+
/* If PF_INET or PF_INET6, check name_bind permission for the port. */
- family = sk->sk_family;
if (family == PF_INET || family == PF_INET6) {
char *addrp;
struct common_audit_data ad;
base-commit: 034294fbfdf0ded4f931f9503d2ca5bbf8b9aebd
--
2.34.1
