From f6c025297e99d250bdadae98a8544ba7cdcf6993 Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Mon, 5 Dec 2016 16:28:28 -0800 Subject: [PATCH] ANDROID: ion: check for kref overflow Userspace can cause the kref to handles to increment arbitrarily high. Ensure it does not overflow. Signed-off-by: Daniel Rosenberg Bug: 31992382 Test: See bug for poc Change-Id: I6bff1df385742b1d836d43180dc87fadcea80782 Git-repo: https://android.googlesource.com/kernel/msm Git-commit: 0c702db4d90de88df11057bcf0d8fb2dfe741605 Signed-off-by: Dennis Cagle --- drivers/staging/android/ion/ion.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c index b7fe42582e89..faa81c28a0d3 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -16,6 +16,7 @@ * */ +#include #include #include #include @@ -402,6 +403,15 @@ static void ion_handle_get(struct ion_handle *handle) kref_get(&handle->ref); } +/* Must hold the client lock */ +static struct ion_handle* ion_handle_get_check_overflow(struct ion_handle *handle) +{ + if (atomic_read(&handle->ref.refcount) + 1 == 0) + return ERR_PTR(-EOVERFLOW); + ion_handle_get(handle); + return handle; +} + static int ion_handle_put_nolock(struct ion_handle *handle) { int ret; @@ -448,9 +458,9 @@ static struct ion_handle *ion_handle_get_by_id_nolock(struct ion_client *client, handle = idr_find(&client->idr, id); if (handle) - ion_handle_get(handle); + return ion_handle_get_check_overflow(handle); - return handle ? handle : ERR_PTR(-EINVAL); + return ERR_PTR(-EINVAL); } struct ion_handle *ion_handle_get_by_id(struct ion_client *client, @@ -1412,7 +1422,7 @@ struct ion_handle *ion_import_dma_buf(struct ion_client *client, int fd) /* if a handle exists for this buffer just take a reference to it */ handle = ion_handle_lookup(client, buffer); if (!IS_ERR(handle)) { - ion_handle_get(handle); + handle = ion_handle_get_check_overflow(handle); mutex_unlock(&client->lock); goto end; } -- 2.11.0