On Fri, Dec 13, 2024 at 5:57 AM Mikhail Ivanov
[off-list ref] wrote:

On 12/12/2024 8:50 PM, Mickaël Salaün wrote:

quoted

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.

quoted

On Thu, Dec 12, 2024 at 06:20:00PM +0800, Mikhail Ivanov wrote:

quoted

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@google.com/ (local)

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Mikhail Ivanov <redacted>
---
  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