Re: linux-next: manual merge of the char-misc.current tree with the mm-hotfixes tree

[Andrew Morton]

On Fri, 19 Aug 2022 13:35:04 +0000 Liam Howlett <liam.howlett@xxxxxxxxxx> wrote:

> b3bb668f3dc6 is the older v1 of the patch [1]. d6f35446d076 from
> mm-hotfixes is the correct v2 version [2], although I don't think that's
> currently in mm-hotfixes-unstable.  It looks like version 1 is now in
> mm-hotfixes-unstable as well.
> 
> 1: https://lore.kernel.org/linux-mm/20220809160618.1052539-1-Liam.Howlett@xxxxxxxxxx/
> 2: https://lore.kernel.org/linux-mm/20220810160209.1630707-1-Liam.Howlett@xxxxxxxxxx/

I moved "binder_alloc: add missing mmap_lock calls when using the VMA"
into mm-hotfixes-stable this week.

It's the v2.  I intend to send this Linuswards today or tomorrow.  Below.

So I think we're all good.


commit b3bb668f3dc6a97a91c47a4cebb0e3f33554c08c
Author: Liam Howlett <liam.howlett@xxxxxxxxxx>
Date:   Wed Aug 10 16:02:25 2022 +0000

    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@xxxxxxxxxx
    Fixes: a43cfc87caaf ("android: binder: stop saving a pointer to the VMA")
    Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
    Reported-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
    Reported-by: <syzbot+a7b60a176ec13cafb793@xxxxxxxxxxxxxxxxxxxxxxxxx>
    Acked-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
    Tested-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
    Cc: Minchan Kim <minchan@xxxxxxxxxx>
    Cc: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx>
    Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Cc: Hridya Valsaraju <hridya@xxxxxxxxxx>
    Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
    Cc: Martijn Coenen <maco@xxxxxxxxxxx>
    Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
    Cc: Todd Kjos <tkjos@xxxxxxxxxxx>
    Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
    Cc: "Arve Hjønnevåg" <arve@xxxxxxxxxxx>
    Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 1014beb12802..d247742bb42e 100644
--- 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 +932,23 @@ 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)
+		goto uninitialized;
+
+	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:
+	mmap_read_unlock(alloc->vma_vm_mm);
 	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);