a7y18lte-ubports/android_kernel_samsung_universal7885
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staging: android: ion: check for kref overflow

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This patch is against 4.4. 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 2018-08-21 13:31:50 -07:00 committed by Greg Kroah-Hartman
parent 81970da691
commit b84ec04bae
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/device.h>
#include <linux/err.h> #include <linux/err.h>
#include <linux/file.h> #include <linux/file.h>
@ -387,6 +388,16 @@ static void ion_handle_get(struct ion_handle *handle)
kref_get(&handle->ref); 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) static int ion_handle_put_nolock(struct ion_handle *handle)
{ {
int ret; int ret;
@ -433,9 +444,9 @@ static struct ion_handle *ion_handle_get_by_id_nolock(struct ion_client *client,
handle = idr_find(&client->idr, id); handle = idr_find(&client->idr, id);
if (handle) 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, struct ion_handle *ion_handle_get_by_id(struct ion_client *client,
@ -1202,7 +1213,7 @@ 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 */ /* if a handle exists for this buffer just take a reference to it */
handle = ion_handle_lookup(client, buffer); handle = ion_handle_lookup(client, buffer);
if (!IS_ERR(handle)) { if (!IS_ERR(handle)) {
ion_handle_get(handle); handle = ion_handle_get_check_overflow(handle);
mutex_unlock(&client->lock); mutex_unlock(&client->lock);
goto end; goto end;
} }