On Wed, Jan 31, 2018 at 04:06:37AM -0500, Paul Moore wrote:

On Tue, Jan 30, 2018 at 5:46 PM, Greg KH [off-list ref] wrote:

quoted

On Tue, Jan 30, 2018 at 11:00:04AM -0800, Mark Salyzyn wrote:

quoted

On 01/19/2018 09:41 AM, Stephen Smalley wrote:

quoted

If we can't safely dereference the sock in these hooks, then that seems
to point back to the approach used in my original code, where in
ancient history I had sock_has_perm() take the socket and use its inode
i_security field instead of the sock.  commit
253bfae6e0ad97554799affa0266052968a45808 switched them to use the sock
instead.

Because of the nature of this problem (hard to duplicate, no clear path), I
am understandably not comfortable reverting and submitting for testing in
order to prove this point. It is disruptive because it changes several
subroutine call signatures.

AFAIK this looks like a user request racing in without reference counting or
RCU grace period in the callers (could be viewed as not an issue with
security code). Effectively fixed in 4.9-stable, but broken in 4.4-stable.

hygiene, KISS and small, is all I do feel comfortable to submit to
4.4-stable without pulling in all the infrastructure improvements.

-- Mark

---
 security/selinux/hooks.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 34427384605d..be68992a28cb 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c

@@ -4066,6 +4066,8 @@ static int sock_has_perm(struct task_struct *task,

struct sock *sk, u32 perms)
     struct lsm_network_audit net = {0,};
     u32 tsid = task_sid(task);

+    if (!sksec)
+        return -EFAULT;
     if (sksec->sid == SECINITSID_KERNEL)
         return 0;

This looks sane to me as a simple 4.4-only fix.  If the SELinux
maintainer acks it, I can easily queue this up.

This revision addresses my concerns with Mark's previous patch.

Acked-by: Paul Moore <paul@paul-moore.com>

Wonderful!

Mark, can you resend this in a format I can apply it in?

thanks,

greg k-h
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