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binder: use cred instead of task for getsecid

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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: ec74136ded ("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>
This commit is contained in:
Todd Kjos 2021-10-12 09:56:14 -07:00 committed by Paul Moore
parent 52f8869337
commit 4d5b553974
2 changed files with 6 additions and 10 deletions
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11
drivers/android/binder.c
View File

@ -2713,16 +2713,7 @@ static void binder_transaction(struct binder_proc *proc,
u32 secid; u32 secid;
size_t added_size; size_t added_size;
/* security_cred_getsecid(proc->cred, &secid);
* 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);
ret = security_secid_to_secctx(secid, &secctx, &secctx_sz); ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
if (ret) { if (ret) {
return_error = BR_FAILED_REPLY; return_error = BR_FAILED_REPLY;

5
include/linux/security.h
View File

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