Commit 44e602b4 authored by Liam Howlett's avatar Liam Howlett Committed by Andrew Morton
Browse files

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: a43cfc87 (android: binder: stop saving a pointer to the VMA)
Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Reported-by: default avatarOndrej Mosnacek <omosnace@redhat.com>
Reported-by: default avatar <syzbot+a7b60a176ec13cafb793@syzkaller.appspotmail.com>
Acked-by: default avatarCarlos Llamas <cmllamas@google.com>
Tested-by: default avatarOndrej 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent fcab34b4

drivers/android/binder_alloc.c

+21 −10
Original line number Diff line number Diff line
@@ -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 *));
@@ -929,7 +932,14 @@ 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) {



	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)
@@ -939,7 +949,8 @@ void binder_alloc_print_pages(struct seq_file *m, 
		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);