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References: <20230922044241.322832-1-cmllamas@google.com> <20230922175138.230331-1-cmllamas@google.com>
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From:   Alice Ryhl <aliceryhl@google.com>
Date:   Fri, 22 Sep 2023 20:50:51 +0200
Message-ID: <CAH5fLgivUrTGxFjmnN2XYv5_hL==A+UfmJibC0vzy4Bw1AMxAQ@mail.gmail.com>
Subject: Re: [PATCH v2] binder: fix memory leaks of spam and pending work
To:     Carlos Llamas <cmllamas@google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>,
        Todd Kjos <tkjos@android.com>,
        Martijn Coenen <maco@android.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        Christian Brauner <brauner@kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Li Li <dualli@google.com>, Hang Lu <hangl@codeaurora.org>,
        linux-kernel@vger.kernel.org, kernel-team@android.com,
        syzkaller-bugs@googlegroups.com, stable@vger.kernel.org,
        syzbot+7f10c1653e35933c0f1e@syzkaller.appspotmail.com,
        Todd Kjos <tkjos@google.com>
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On Fri, Sep 22, 2023 at 7:51=E2=80=AFPM Carlos Llamas <cmllamas@google.com>=
 wrote:
>
> A transaction complete work is allocated and queued for each
> transaction. Under certain conditions the work->type might be marked as
> BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT to notify userspace about
> potential spamming threads or as BINDER_WORK_TRANSACTION_PENDING when
> the target is currently frozen.
>
> However, these work types are not being handled in binder_release_work()
> so they will leak during a cleanup. This was reported by syzkaller with
> the following kmemleak dump:
>
> BUG: memory leak
> unreferenced object 0xffff88810e2d6de0 (size 32):
>   comm "syz-executor338", pid 5046, jiffies 4294968230 (age 13.590s)
>   hex dump (first 32 bytes):
>     e0 6d 2d 0e 81 88 ff ff e0 6d 2d 0e 81 88 ff ff  .m-......m-.....
>     04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff81573b75>] kmalloc_trace+0x25/0x90 mm/slab_common.c:1114
>     [<ffffffff83d41873>] kmalloc include/linux/slab.h:599 [inline]
>     [<ffffffff83d41873>] kzalloc include/linux/slab.h:720 [inline]
>     [<ffffffff83d41873>] binder_transaction+0x573/0x4050 drivers/android/=
binder.c:3152
>     [<ffffffff83d45a05>] binder_thread_write+0x6b5/0x1860 drivers/android=
/binder.c:4010
>     [<ffffffff83d486dc>] binder_ioctl_write_read drivers/android/binder.c=
:5066 [inline]
>     [<ffffffff83d486dc>] binder_ioctl+0x1b2c/0x3cf0 drivers/android/binde=
r.c:5352
>     [<ffffffff816b25f2>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff816b25f2>] __do_sys_ioctl fs/ioctl.c:871 [inline]
>     [<ffffffff816b25f2>] __se_sys_ioctl fs/ioctl.c:857 [inline]
>     [<ffffffff816b25f2>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:857
>     [<ffffffff84b30008>] do_syscall_x64 arch/x86/entry/common.c:50 [inlin=
e]
>     [<ffffffff84b30008>] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:=
80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Fix the leaks by kfreeing these work types in binder_release_work() and
> handle them as a BINDER_WORK_TRANSACTION_COMPLETE cleanup.
>
> Cc: stable@vger.kernel.org
> Fixes: 0567461a7a6e ("binder: return pending info for frozen async txns")
> Fixes: a7dc1e6f99df ("binder: tell userspace to dump current backtrace wh=
en detected oneway spamming")
> Reported-by: syzbot+7f10c1653e35933c0f1e@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=3D7f10c1653e35933c0f1e
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Carlos Llamas <cmllamas@google.com>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>