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staging: android: ion: check for kref overflow

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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 <drosen@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Rosenberg 2018-08-30 16:09:46 -07:00 committed by Greg Kroah-Hartman
parent b8c0e15469
commit 3af20bddda
1 changed files with 14 additions and 3 deletions
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17
drivers/staging/android/ion/ion.c
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@ -15,6 +15,7 @@
*
*/
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/file.h>
@ -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;
}