From: Liam Howlett liam.howlett@oracle.com
commit 44e602b4e52f70f04620bbbf4fe46ecb40170bde upstream.
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: a43cfc87caaf (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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/binder_alloc.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-)
--- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -395,12 +395,15 @@ static struct binder_buffer *binder_allo 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 *)); @@ -922,17 +925,25 @@ void binder_alloc_print_pages(struct seq * 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);