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