linux-kernel - Re: [PATCH 17/21] binder: malloc new

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Date:   Fri, 1 Dec 2023 07:20:36 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     Alice Ryhl <aliceryhl@...gle.com>
Cc:     Arve Hjønnevåg <arve@...roid.com>,
        Christian Brauner <brauner@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org,
        Martijn Coenen <maco@...roid.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Todd Kjos <tkjos@...roid.com>
Subject: Re: [PATCH 17/21] binder: malloc new_buffer outside of locks

On Tue, Nov 07, 2023 at 09:08:38AM +0000, Alice Ryhl wrote:
> Carlos Llamas <cmllamas@...gle.com> writes:
> > Preallocate new_buffer before acquiring the alloc->mutex and hand it
> > down to binder_alloc_new_buf_locked(). The new buffer will be used in
> > the vast majority of requests (measured at 98.2% in field data). The
> > buffer is discarded otherwise. This change is required in preparation
> > for transitioning alloc->mutex into a spinlock in subsequent commits.
> > 
> > Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
> 
> You also need to free the new buffer here:
> 
> 	if (unlikely(!best_fit)) {
> 		binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
> 				   "%d: binder_alloc_buf size %zd failed, no address space\n",
> 				   alloc->pid, size);
> 		debug_no_space_locked(alloc);
> 		return ERR_PTR(-ENOSPC);
> 	}

Ouch! this is true and there is a second instance that needs the kfree
as well. Thanks for catching it.

--
Carlos Llamas