[PATCH AUTOSEL 6.11 230/244] random: vDSO: avoid call to out of line memset()

Sasha Levin
2024-09-25T11:53:10Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ Upstream commit b7bad082e113640fc81200ff869e5c2d7a9c29a2 ]

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: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/vdso/getrandom.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c
index bacf19dbb6a11..1281fa3546c20 100644
--- a/lib/vdso/getrandom.c
+++ b/lib/vdso/getrandom.c
@@ -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;
}

--
2.43.0