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.
Fixes: ec74136ded79 ("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 Cc: stable@vger.kernel.org # 5.4+ --- v3: added this patch to series v4: fix build-break for !CONFIG_SECURITY v5: set *secid=0 for !CONFIG_SECURITY version of secuirty_cred_getsecid()
drivers/android/binder.c | 11 +---------- include/linux/security.h | 5 +++++ 2 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c index bc15325f0579..26382e982c5e 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2722,16 +2722,7 @@ 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; diff --git a/include/linux/security.h b/include/linux/security.h index 6344d3362df7..46a02ce34d00 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -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;