binder: fix proc->files use-after-free

proc->files cleanup is initiated by binder_vma_close. Therefore
a reference on the binder_proc is not enough to prevent the
files_struct from being released while the binder_proc still has
a reference. This can lead to an attempt to dereference the
stale pointer obtained from proc->files prior to proc->files
cleanup. This has been seen once in task_get_unused_fd_flags()
when __alloc_fd() is called with a stale "files".

The fix is to protect proc->files with a mutex to prevent cleanup
while in use.

Bug: 69164715
Change-Id: I90fc117e004ecefc5336779cd7cd24faad37bd86
Signed-off-by: Todd Kjos <tkjos@google.com>

0 files changed, 0 insertions, 0 deletions