Messages in this thread | | | Date | Tue, 2 Aug 2022 10:13:20 +0200 | From | Christian Brauner <> | Subject | Re: [PATCH] binder: fix UAF of ref->proc caused by race condition |
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On Mon, Aug 01, 2022 at 06:25:11PM +0000, Carlos Llamas wrote: > A transaction of type BINDER_TYPE_WEAK_HANDLE can fail to increment the > reference for a node. In this case, the target proc normally releases > the failed reference upon close as expected. However, if the target is > dying in parallel the call will race with binder_deferred_release(), so > the target could have released all of its references by now leaving the > cleanup of the new failed reference unhandled. > > The transaction then ends and the target proc gets released making the > ref->proc now a dangling pointer. Later on, ref->node is closed and we > attempt to take spin_lock(&ref->proc->inner_lock), which leads to the > use-after-free bug reported below. Let's fix this by cleaning up the > failed reference on the spot instead of relying on the target to do so. > > ================================================================== > BUG: KASAN: use-after-free in _raw_spin_lock+0xa8/0x150 > Write of size 4 at addr ffff5ca207094238 by task kworker/1:0/590 > > CPU: 1 PID: 590 Comm: kworker/1:0 Not tainted 5.19.0-rc8 #10 > Hardware name: linux,dummy-virt (DT) > Workqueue: events binder_deferred_func > Call trace: > dump_backtrace.part.0+0x1d0/0x1e0 > show_stack+0x18/0x70 > dump_stack_lvl+0x68/0x84 > print_report+0x2e4/0x61c > kasan_report+0xa4/0x110 > kasan_check_range+0xfc/0x1a4 > __kasan_check_write+0x3c/0x50 > _raw_spin_lock+0xa8/0x150 > binder_deferred_func+0x5e0/0x9b0 > process_one_work+0x38c/0x5f0 > worker_thread+0x9c/0x694 > kthread+0x188/0x190 > ret_from_fork+0x10/0x20 > > Signed-off-by: Carlos Llamas <cmllamas@google.com> > ---
Seems sane, Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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