diff options
author | Jann Horn <jannh@google.com> | 2019-10-18 23:56:29 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-12-13 10:43:23 +0300 |
commit | 6e0efd9e9e0549099ff428a88f6d73fb4653c947 (patch) | |
tree | c89ed44a4b5618bb1df6f5455b4da2d1d78a5454 /drivers/android | |
parent | 0bbb506cd52f8090ecdd32b2c2bdf8f93425ec73 (diff) | |
download | linux-6e0efd9e9e0549099ff428a88f6d73fb4653c947.tar.xz |
binder: Fix race between mmap() and binder_alloc_print_pages()
commit 8eb52a1ee37aafd9b796713aa0b3ab9cbc455be3 upstream.
binder_alloc_print_pages() iterates over
alloc->pages[0..alloc->buffer_size-1] under alloc->mutex.
binder_alloc_mmap_handler() writes alloc->pages and alloc->buffer_size
without holding that lock, and even writes them before the last bailout
point.
Unfortunately we can't take the alloc->mutex in the ->mmap() handler
because mmap_sem can be taken while alloc->mutex is held.
So instead, we have to locklessly check whether the binder_alloc has been
fully initialized with binder_alloc_get_vma(), like in
binder_alloc_new_buf_locked().
Fixes: 8ef4665aa129 ("android: binder: Add page usage in binder stats")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20191018205631.248274-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android')
-rw-r--r-- | drivers/android/binder_alloc.c | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index eb76a823fbb2..21952dfa147d 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -841,14 +841,20 @@ void binder_alloc_print_pages(struct seq_file *m, int free = 0; mutex_lock(&alloc->mutex); - 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++; + /* + * 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++; + } } mutex_unlock(&alloc->mutex); seq_printf(m, " pages: %d:%d:%d\n", active, lru, free); |