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

[Sasha Levin]

From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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@xxxxxxxxx>. 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