From 3af20bddda6f24b5a1c0072f2f6e3bb3ed04bf78 Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Thu, 30 Aug 2018 16:09:46 -0700 Subject: staging: android: ion: check for kref overflow This patch is against 4.9. It does not apply to master due to a large rework of ion in 4.12 which removed the affected functions altogther. 4c23cbff073f3b9b ("staging: android: ion: Remove import interface") Userspace can cause the kref to handles to increment arbitrarily high. Ensure it does not overflow. Signed-off-by: Daniel Rosenberg Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ion/ion.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c index 403df8bf4b48..806e9b30b9dc 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -15,6 +15,7 @@ * */ +#include #include #include #include @@ -305,6 +306,16 @@ 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; +} + int ion_handle_put_nolock(struct ion_handle *handle) { return kref_put(&handle->ref, ion_handle_destroy); @@ -347,9 +358,9 @@ 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); } static bool ion_handle_validate(struct ion_client *client, @@ -1110,7 +1121,7 @@ struct ion_handle *ion_import_dma_buf(struct ion_client *client, /* 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; } -- cgit v1.2.3