binder_alloc: add missing mmap_lock calls when using the VMA

Take the mmap_read_lock() when using the VMA in binder_alloc_print_pages()
and when checking for a VMA in binder_alloc_new_buf_locked().

It is worth noting binder_alloc_new_buf_locked() drops the VMA read lock
after it verifies a VMA exists, but may be taken again deeper in the call
stack, if necessary.

Link: https://lkml.kernel.org/r/20220810160209.1630707-1-Liam.Howlett@oracle.com
Fixes: 6b4465651707 (android: binder: stop saving a pointer to the VMA)
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: Ondrej Mosnacek <omosnace@redhat.com>
Reported-by: <syzbot+a7b60a176ec13cafb793@syzkaller.appspotmail.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Tested-by: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Christian Brauner (Microsoft) <brauner@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hridya Valsaraju <hridya@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Martijn Coenen <maco@android.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Todd Kjos <tkjos@android.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Arve Hjønnevåg" <arve@android.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 1014beb128025706ac6d98d7e09a6030acb5c23f..51f4e1c5cd0199bbd34d886dd3e08c4f6664507e 100644 (file)
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -402,12 +402,15 @@ static struct binder_buffer *binder_alloc_new_buf_locked(
        size_t size, data_offsets_size;
        int ret;
 
+       mmap_read_lock(alloc->vma_vm_mm);
        if (!binder_alloc_get_vma(alloc)) {
+               mmap_read_unlock(alloc->vma_vm_mm);
                binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
                                   "%d: binder_alloc_buf, no vma\n",
                                   alloc->pid);
                return ERR_PTR(-ESRCH);
        }
+       mmap_read_unlock(alloc->vma_vm_mm);
 
        data_offsets_size = ALIGN(data_size, sizeof(void *)) +
                ALIGN(offsets_size, sizeof(void *));
@@ -929,17 +932,25 @@ void binder_alloc_print_pages(struct seq_file *m,
         * Make sure the binder_alloc is fully initialized, otherwise we might
         * read inconsistent state.
         */
-       if (binder_alloc_get_vma(alloc) != NULL) {
-               for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
-                       page = &alloc->pages[i];
-                       if (!page->page_ptr)
-                               free++;
-                       else if (list_empty(&page->lru))
-                               active++;
-                       else
-                               lru++;
-               }
+
+       mmap_read_lock(alloc->vma_vm_mm);
+       if (binder_alloc_get_vma(alloc) == NULL) {
+               mmap_read_unlock(alloc->vma_vm_mm);
+               goto uninitialized;
        }
+
+       mmap_read_unlock(alloc->vma_vm_mm);
+       for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) {
+               page = &alloc->pages[i];
+               if (!page->page_ptr)
+                       free++;
+               else if (list_empty(&page->lru))
+                       active++;
+               else
+                       lru++;
+       }
+
+uninitialized:
        mutex_unlock(&alloc->mutex);
        seq_printf(m, "  pages: %d:%d:%d\n", active, lru, free);
        seq_printf(m, "  pages high watermark: %zu\n", alloc->pages_high);