BACKPORT: binder: use cred instead of task for selinux checks
Since binder was integrated with selinux, it has passed
'struct task_struct' associated with the binder_proc
to represent the source and target of transactions.
The conversion of task to SID was then done in the hook
implementations. It turns out that there are race conditions
which can result in an incorrect security context being used.
Fix by using the 'struct cred' saved during binder_open and pass
it to the selinux subsystem.
Cc: stable@vger.kernel.org # 5.14 (need backport for earlier stables)
Fixes: 79af73079d75 ("Add security hooks to binder and implement the hooks for SELinux.")
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Bug: 200688826
(cherry picked from commit 52f88693378a58094c538662ba652aff0253c4fe)
[ refactored to avoid changing KMI: struct binder_proc ]
Change-Id: I1664c1f0c2142c17e9ca0d6790bb94de79f531e3
diff --git a/security/security.c b/security/security.c
index cf8ddca..1e0f79c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -689,25 +689,25 @@ static void __init lsm_early_task(struct task_struct *task)
/* Security operations */
-int security_binder_set_context_mgr(struct task_struct *mgr)
+int security_binder_set_context_mgr(const struct cred *mgr)
{
return call_int_hook(binder_set_context_mgr, 0, mgr);
}
-int security_binder_transaction(struct task_struct *from,
- struct task_struct *to)
+int security_binder_transaction(const struct cred *from,
+ const struct cred *to)
{
return call_int_hook(binder_transaction, 0, from, to);
}
-int security_binder_transfer_binder(struct task_struct *from,
- struct task_struct *to)
+int security_binder_transfer_binder(const struct cred *from,
+ const struct cred *to)
{
return call_int_hook(binder_transfer_binder, 0, from, to);
}
-int security_binder_transfer_file(struct task_struct *from,
- struct task_struct *to, struct file *file)
+int security_binder_transfer_file(const struct cred *from,
+ const struct cred *to, struct file *file)
{
return call_int_hook(binder_transfer_file, 0, from, to, file);
}