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binder: fix possible UAF when freeing buffer
commit a370003cc3
upstream.
There is a race between the binder driver cleaning
up a completed transaction via binder_free_transaction()
and a user calling binder_ioctl(BC_FREE_BUFFER) to
release a buffer. It doesn't matter which is first but
they need to be protected against running concurrently
which can result in a UAF.
Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
ba2c247a45
commit
22068d49d0
1 changed files with 14 additions and 2 deletions
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@ -1960,8 +1960,18 @@ static struct binder_thread *binder_get_txn_from_and_acq_inner(
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static void binder_free_transaction(struct binder_transaction *t)
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{
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if (t->buffer)
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t->buffer->transaction = NULL;
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struct binder_proc *target_proc = t->to_proc;
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if (target_proc) {
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binder_inner_proc_lock(target_proc);
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if (t->buffer)
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t->buffer->transaction = NULL;
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binder_inner_proc_unlock(target_proc);
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}
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/*
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* If the transaction has no target_proc, then
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* t->buffer->transaction has already been cleared.
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*/
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kfree(t);
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binder_stats_deleted(BINDER_STAT_TRANSACTION);
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}
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@ -3484,10 +3494,12 @@ static int binder_thread_write(struct binder_proc *proc,
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buffer->debug_id,
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buffer->transaction ? "active" : "finished");
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binder_inner_proc_lock(proc);
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if (buffer->transaction) {
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buffer->transaction->buffer = NULL;
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buffer->transaction = NULL;
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}
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binder_inner_proc_unlock(proc);
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if (buffer->async_transaction && buffer->target_node) {
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struct binder_node *buf_node;
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struct binder_work *w;
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