Commit b7bad082 authored by Christophe Leroy's avatar Christophe Leroy Committed by Jason A. Donenfeld
Browse files

random: vDSO: avoid call to out of line memset() 



With the current implementation, __cvdso_getrandom_data() calls
memset() on certain architectures, which is unexpected in the VDSO.

Rather than providing a memset(), simply rewrite opaque data
initialization to avoid memset().

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
parent 81723e3a

lib/vdso/getrandom.c

+7 −5
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
 * Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.

 */



#include <linux/array_size.h>

#include <linux/cache.h>

#include <linux/kernel.h>

#include <linux/time64.h>
@@ -73,11 +74,12 @@ __cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, size_ 
	u32 counter[2] = { 0 };



	if (unlikely(opaque_len == ~0UL && !buffer && !len && !flags)) {

		*(struct vgetrandom_opaque_params *)opaque_state = (struct vgetrandom_opaque_params) {

			.size_of_opaque_state = sizeof(*state),

			.mmap_prot = PROT_READ | PROT_WRITE,

			.mmap_flags = MAP_DROPPABLE | MAP_ANONYMOUS

		};

		struct vgetrandom_opaque_params *params = opaque_state;

		params->size_of_opaque_state = sizeof(*state);

		params->mmap_prot = PROT_READ | PROT_WRITE;

		params->mmap_flags = MAP_DROPPABLE | MAP_ANONYMOUS;

		for (size_t i = 0; i < ARRAY_SIZE(params->reserved); ++i)

			params->reserved[i] = 0;

		return 0;

	}