From: Todd Kjos tkjos@google.com
commit 5fdb55c1ac9585eb23bb2541d5819224429e103d upstream.
During BC_FREE_BUFFER processing, the BINDER_TYPE_FDA object cleanup may close 1 or more fds. The close operations are completed using the task work mechanism -- which means the thread needs to return to userspace or the file object may never be dereferenced -- which can lead to hung processes.
Force the binder thread back to userspace if an fd is closed during BC_FREE_BUFFER handling.
Fixes: 80cd795630d6 ("binder: fix use-after-free due to ksys_close() during fdget()") Cc: stable stable@vger.kernel.org Reviewed-by: Martijn Coenen maco@android.com Acked-by: Christian Brauner christian.brauner@ubuntu.com Signed-off-by: Todd Kjos tkjos@google.com Link: https://lore.kernel.org/r/20210830195146.587206-1-tkjos@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/binder.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-)
--- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2236,6 +2236,7 @@ static void binder_deferred_fd_close(int }
static void binder_transaction_buffer_release(struct binder_proc *proc, + struct binder_thread *thread, struct binder_buffer *buffer, binder_size_t failed_at, bool is_failure) @@ -2395,8 +2396,16 @@ static void binder_transaction_buffer_re &proc->alloc, &fd, buffer, offset, sizeof(fd)); WARN_ON(err); - if (!err) + if (!err) { binder_deferred_fd_close(fd); + /* + * Need to make sure the thread goes + * back to userspace to complete the + * deferred close + */ + if (thread) + thread->looper_need_return = true; + } } } break; default: @@ -3465,7 +3474,7 @@ err_bad_parent: err_copy_data_failed: binder_free_txn_fixups(t); trace_binder_transaction_failed_buffer_release(t->buffer); - binder_transaction_buffer_release(target_proc, t->buffer, + binder_transaction_buffer_release(target_proc, NULL, t->buffer, buffer_offset, true); if (target_node) binder_dec_node_tmpref(target_node); @@ -3542,7 +3551,9 @@ err_invalid_target_handle: * Cleanup buffer and free it. */ static void -binder_free_buf(struct binder_proc *proc, struct binder_buffer *buffer) +binder_free_buf(struct binder_proc *proc, + struct binder_thread *thread, + struct binder_buffer *buffer) { binder_inner_proc_lock(proc); if (buffer->transaction) { @@ -3570,7 +3581,7 @@ binder_free_buf(struct binder_proc *proc binder_node_inner_unlock(buf_node); } trace_binder_transaction_buffer_release(buffer); - binder_transaction_buffer_release(proc, buffer, 0, false); + binder_transaction_buffer_release(proc, thread, buffer, 0, false); binder_alloc_free_buf(&proc->alloc, buffer); }
@@ -3771,7 +3782,7 @@ static int binder_thread_write(struct bi proc->pid, thread->pid, (u64)data_ptr, buffer->debug_id, buffer->transaction ? "active" : "finished"); - binder_free_buf(proc, buffer); + binder_free_buf(proc, thread, buffer); break; }
@@ -4459,7 +4470,7 @@ retry: buffer->transaction = NULL; binder_cleanup_transaction(t, "fd fixups failed", BR_FAILED_REPLY); - binder_free_buf(proc, buffer); + binder_free_buf(proc, thread, buffer); binder_debug(BINDER_DEBUG_FAILED_TRANSACTION, "%d:%d %stransaction %d fd fixups failed %d/%d, line %d\n", proc->pid, thread->pid,