On Thu, Nov 25, 2021 at 02:20:04PM +0000, Lee Jones wrote:
> Supply additional checks in order to prevent unexpected results.
>
> Fixes: b892bf75b2034 ("ion: Switch ion to use dma-buf")
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
> Should be back-ported from v4.9 and earlier.
>
> drivers/staging/android/ion/ion.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index 806e9b30b9dc8..402b74f5d7e69 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -29,6 +29,7 @@
> #include <linux/export.h>
> #include <linux/mm.h>
> #include <linux/mm_types.h>
> +#include <linux/overflow.h>
> #include <linux/rbtree.h>
> #include <linux/slab.h>
> #include <linux/seq_file.h>
> @@ -509,6 +510,10 @@ static void *ion_handle_kmap_get(struct ion_handle *handle)
> void *vaddr;
>
> if (handle->kmap_cnt) {
> + if (check_add_overflow(handle->kmap_cnt,
> + (unsigned int) 1, &handle->kmap_cnt))
^^^^^^^^^^^^^^^^^
> + return ERR_PTR(-EOVERFLOW);
> +
> handle->kmap_cnt++;
^^^^^^^^^^^^^^^^^^^
This will not do what you want at all. It's a double increment on the
success path and it leave handle->kmap_cnt overflowed on failure path.
regards,
dan carpenter
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