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    Subject[PATCH 3.16 246/410] binder: check for binder_thread allocation failure in binder_poll()
    3.16.57-rc1 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")
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    [bwh: Backported to 3.16:
    - Drop the binder global lock before returning
    - Adjust filename]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    --- a/drivers/staging/android/binder.c
    +++ b/drivers/staging/android/binder.c
    @@ -2572,6 +2572,10 @@ static unsigned int binder_poll(struct f
    binder_lock(__func__);

    thread = binder_get_thread(proc);
    + if (!thread) {
    + binder_unlock(__func__);
    + return POLLERR;
    + }

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