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UPSTREAM: binder: use euid from cred instead of using task

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commit 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b upstream.

Save the 'struct cred' associated with a binder process
at initial open to avoid potential race conditions
when converting to an euid.

Set a transaction's sender_euid from the 'struct cred'
saved at binder_open() instead of looking up the euid
from the binder proc's 'struct task'. This ensures
the euid is associated with the security context that
of the task that opened binder.

Cc: stable@vger.kernel.org # 4.4+
Fixes: 457b9a6f09 ("Staging: android: add binder driver")
Signed-off-by: Todd Kjos <tkjos@google.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Suggested-by: Jann Horn <jannh@google.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Change-Id: I91922e7f359df5901749f1b09094c3c68d45aed4
Bug: 200688826
Signed-off-by: Todd Kjos <tkjos@google.com>
This commit is contained in:
Todd Kjos
2021-10-12 09:56:12 -07:00
parent 4b0d5f0342
commit 6ada76218a
1 changed files with 7 additions and 1 deletions
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8
drivers/android/binder.c
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@@ -459,6 +459,9 @@ struct binder_priority {
* @files files_struct for process * @files files_struct for process
* (protected by @files_lock) * (protected by @files_lock)
* @files_lock mutex to protect @files * @files_lock mutex to protect @files
* @cred struct cred associated with the `struct file`
* in binder_open()
* (invariant after initialized)
* @deferred_work_node: element for binder_deferred_list * @deferred_work_node: element for binder_deferred_list
* (protected by binder_deferred_lock) * (protected by binder_deferred_lock)
* @deferred_work: bitmap of deferred work to perform * @deferred_work: bitmap of deferred work to perform
@@ -506,6 +509,7 @@ struct binder_proc {
struct task_struct *tsk; struct task_struct *tsk;
struct files_struct *files; struct files_struct *files;
struct mutex files_lock; struct mutex files_lock;
const struct cred *cred;
struct hlist_node deferred_work_node; struct hlist_node deferred_work_node;
int deferred_work; int deferred_work;
bool is_dead; bool is_dead;
@@ -3175,7 +3179,7 @@ static void binder_transaction(struct binder_proc *proc,
t->from = thread; t->from = thread;
else else
t->from = NULL; t->from = NULL;
t->sender_euid = task_euid(proc->tsk); t->sender_euid = proc->cred->euid;
t->to_proc = target_proc; t->to_proc = target_proc;
t->to_thread = target_thread; t->to_thread = target_thread;
t->code = tr->code; t->code = tr->code;
@@ -4660,6 +4664,7 @@ static void binder_free_proc(struct binder_proc *proc)
} }
binder_alloc_deferred_release(&proc->alloc); binder_alloc_deferred_release(&proc->alloc);
put_task_struct(proc->tsk); put_task_struct(proc->tsk);
put_cred(proc->cred);
binder_stats_deleted(BINDER_STAT_PROC); binder_stats_deleted(BINDER_STAT_PROC);
kfree(proc); kfree(proc);
} }
@@ -5189,6 +5194,7 @@ static int binder_open(struct inode *nodp, struct file *filp)
get_task_struct(current->group_leader); get_task_struct(current->group_leader);
proc->tsk = current->group_leader; proc->tsk = current->group_leader;
mutex_init(&proc->files_lock); mutex_init(&proc->files_lock);
proc->cred = get_cred(filp->f_cred);
INIT_LIST_HEAD(&proc->todo); INIT_LIST_HEAD(&proc->todo);
if (binder_supported_policy(current->policy)) { if (binder_supported_policy(current->policy)) {
proc->default_priority.sched_policy = current->policy; proc->default_priority.sched_policy = current->policy;