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    Subject[PATCH 4.4 027/193] binder: check for binder_thread allocation failure in binder_poll()
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Biggers <ebiggers@google.com>

    commit f88982679f54f75daa5b8eff3da72508f1e7422f upstream.

    If the kzalloc() in binder_get_thread() fails, binder_poll()
    dereferences the resulting NULL pointer.

    Fix it by returning POLLERR if the memory allocation failed.

    This bug was found by syzkaller using fault injection.

    Reported-by: syzbot <syzkaller@googlegroups.com>
    Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
    Cc: stable@vger.kernel.org
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/android/binder.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/android/binder.c
    +++ b/drivers/android/binder.c
    @@ -2622,6 +2622,8 @@ static unsigned int binder_poll(struct f
    binder_lock(__func__);

    thread = binder_get_thread(proc);
    + if (!thread)
    + return POLLERR;

    wait_for_proc_work = thread->transaction_stack == NULL &&
    list_empty(&thread->todo) && thread->return_error == BR_OK;

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