linux-kernel - [PATCH 5/9] vdso: Avoid call to memset() by getrandom

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Message-ID: <a6183ad90ec4834a10f8c751018cca7ca41059a1.1723817900.git.christophe.leroy@csgroup.eu>
Date: Fri, 16 Aug 2024 16:36:52 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"Theodore Ts'o" <tytso@....edu>,
	"Jason A. Donenfeld" <Jason@...c4.com>,
	Andy Lutomirski <luto@...nel.org>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	Arnd Bergmann <arnd@...db.de>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-arch@...r.kernel.org
Subject: [PATCH 5/9] vdso: Avoid call to memset() by getrandom

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

Rewrite opaque data initialisation to avoid memset().

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 lib/vdso/getrandom.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c
index b230f0b10832..425a422651de 100644
--- a/lib/vdso/getrandom.c
+++ b/lib/vdso/getrandom.c
@@ -73,11 +73,15 @@ __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;
+		int i;
+
+		params->size_of_opaque_state = sizeof(*state);
+		params->mmap_prot = PROT_READ | PROT_WRITE;
+		params->mmap_flags = MAP_DROPPABLE | MAP_ANONYMOUS;
+		for (i = 0; i < ARRAY_SIZE(params->reserved); i++)
+			params->reserved[i] = 0;
+
 		return 0;
 	}
 
-- 
2.44.0