Commit 4d5b5539 authored Oct 12, 2021 by Todd Kjos Committed by Paul Moore Oct 14, 2021

binder: use cred instead of task for getsecid



Use the 'struct cred' saved at binder_open() to lookup
the security ID via security_cred_getsecid(). This
ensures that the security context that opened binder
is the one used to generate the secctx.

Cc: stable@vger.kernel.org # 5.4+
Fixes: ec74136d ("binder: create node flag to request sender's security context")
Signed-off-by: Todd Kjos <tkjos@google.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

parent 52f88693

drivers/android/binder.c

+1 −10

Original line number	Diff line number	Diff line
		@@ -2713,16 +2713,7 @@ static void binder_transaction(struct binder_proc *proc,
		u32 secid;
		size_t added_size;

		/*
		* Arguably this should be the task's subjective LSM secid but
		* we can't reliably access the subjective creds of a task
		* other than our own so we must use the objective creds, which
		* are safe to access. The downside is that if a task is
		* temporarily overriding it's creds it will not be reflected
		* here; however, it isn't clear that binder would handle that
		* case well anyway.
		*/
		security_task_getsecid_obj(proc->tsk, &secid);
		security_cred_getsecid(proc->cred, &secid);
		ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
		if (ret) {
		return_error = BR_FAILED_REPLY;

include/linux/security.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -1041,6 +1041,11 @@ static inline void security_transfer_creds(struct cred *new,
		{
		}

		static inline void security_cred_getsecid(const struct cred c, u32 secid)
		{
		*secid = 0;
		}

		static inline int security_kernel_act_as(struct cred *cred, u32 secid)
		{
		return 0;