Re: [PATCH] tee: shm: reject zero-sized allocations in tee_dyn_shm_alloc_helper()

[Sumit Garg]

On Mon, 28 Sep 2026 at 17:31:13 +0300, Georgiy Osokin wrote:
> tee_dyn_shm_alloc_helper() derives nr_pages from a caller-supplied size
> and passes it to alloc_pages_exact() without checking it. For size == 0
> nr_pages is 0, and alloc_pages_exact(0) calls get_order(0), which is
> documented as undefined and returns BITS_PER_LONG - PAGE_SHIFT. The page
> allocator then trips its order > MAX_PAGE_ORDER warning and fails the
> allocation; on a panic_on_warn kernel that ends the boot.
>
> This can be triggered by TEE_IOC_SHM_ALLOC with struct
> tee_ioctl_shm_alloc_data where size is 0.
>
> Reject a zero page count, as register_shm_helper() already does for the
> register path.
>
> Fixes: cf4441503e20 ("tee: optee: Move pool_op helper functions")
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: lvc-project@xxxxxxxxxxxxxxxx
> Signed-off-by: Georgiy Osokin <g.osokin@xxxxxxxxxxxx>
> ---
> drivers/tee/tee_shm.c | 4 ++++
> 1 file changed, 4 insertions(+)

Reviewed-by: Sumit Garg <sumit.garg@xxxxxxxxxxxxxxxx>

-Sumit

> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 6742b3579..daa4af1e0 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -343,6 +343,10 @@ int tee_dyn_shm_alloc_helper(struct tee_shm *shm, size_t size, size_t align,
> 	unsigned int i;
> 	int rc = 0;
>
> +	/* get_order(0) is undefined and exceeds MAX_PAGE_ORDER. */
> +	if (!nr_pages)
> +		return -EINVAL;
> +
> 	/*
> 	 * Ignore alignment since this is already going to be page aligned
> 	 * and there's no need for any larger alignment.
>
> base-commit: 72d3fcf802c45d00b300f25b848a93c3a2bd7c7e
> --
> 2.54.0