From: Alessandro Astone ales.astone@gmail.com
commit ef38de9217a04c9077629a24652689d8fdb4c6c6 upstream.
Some android userspace is sending BINDER_TYPE_FDA objects with num_fds=0. Like the previous patch, this is reproducible when playing a video.
Before commit 09184ae9b575 BINDER_TYPE_FDA objects with num_fds=0 were 'correctly handled', as in no fixup was performed.
After commit 09184ae9b575 we aggregate fixup and skip regions in binder_ptr_fixup structs and distinguish between the two by using the skip_size field: if it's 0, then it's a fixup, otherwise skip. When processing BINDER_TYPE_FDA objects with num_fds=0 we add a skip region of skip_size=0, and this causes issues because now binder_do_deferred_txn_copies will think this was a fixup region.
To address that, return early from binder_translate_fd_array to avoid adding an empty skip region.
Fixes: 09184ae9b575 ("binder: defer copies of pre-patched txn data") Acked-by: Todd Kjos tkjos@google.com Cc: stable stable@kernel.org Signed-off-by: Alessandro Astone ales.astone@gmail.com Link: https://lore.kernel.org/r/20220415120015.52684-1-ales.astone@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Carlos Llamas cmllamas@google.com Signed-off-by: Lee Jones lee@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/binder.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2527,6 +2527,9 @@ static int binder_translate_fd_array(str struct binder_proc *proc = thread->proc; int ret;
+ if (fda->num_fds == 0) + return 0; + fd_buf_size = sizeof(u32) * fda->num_fds; if (fda->num_fds >= SIZE_MAX / sizeof(u32)) { binder_user_error("%d:%d got transaction with invalid number of fds (%lld)\n",