* [PATCH] s390/speculation: Use statically initialized const for instructions
@ 2021-06-16 20:18 Kees Cook
2021-06-22 14:16 ` Vasily Gorbik
0 siblings, 1 reply; 2+ messages in thread
From: Kees Cook @ 2021-06-16 20:18 UTC (permalink / raw)
To: Heiko Carstens
Cc: Kees Cook, Vasily Gorbik, Christian Borntraeger, Sven Schnelle,
linux-kernel, linux-s390, linux-hardening
In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
confusing the checks when using a static const source.
Move the static const array into a variable so the compiler can perform
appropriate bounds checking.
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/s390/kernel/nospec-branch.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
index 2c5c3756644b..250e4dbf653c 100644
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -99,6 +99,7 @@ early_param("spectre_v2", spectre_v2_setup_early);
static void __init_or_module __nospec_revert(s32 *start, s32 *end)
{
enum { BRCL_EXPOLINE, BRASL_EXPOLINE } type;
+ static const u8 branch[] = { 0x47, 0x00, 0x07, 0x00 };
u8 *instr, *thunk, *br;
u8 insnbuf[6];
s32 *epo;
@@ -128,7 +129,7 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end)
if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0)
continue;
- memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4);
+ memcpy(insnbuf + 2, branch, sizeof(branch));
switch (type) {
case BRCL_EXPOLINE:
insnbuf[0] = br[0];
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] s390/speculation: Use statically initialized const for instructions
2021-06-16 20:18 [PATCH] s390/speculation: Use statically initialized const for instructions Kees Cook
@ 2021-06-22 14:16 ` Vasily Gorbik
0 siblings, 0 replies; 2+ messages in thread
From: Vasily Gorbik @ 2021-06-22 14:16 UTC (permalink / raw)
To: Kees Cook
Cc: Heiko Carstens, Christian Borntraeger, Sven Schnelle,
linux-kernel, linux-s390, linux-hardening
On Wed, Jun 16, 2021 at 01:18:23PM -0700, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memcpy(), memmove(), and memset(), avoid
> confusing the checks when using a static const source.
>
> Move the static const array into a variable so the compiler can perform
> appropriate bounds checking.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> arch/s390/kernel/nospec-branch.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
Applied, thanks!
^ permalink raw reply [flat|nested] 2+ messages in thread
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