From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com,
Ard Biesheuvel <ardb@kernel.org>,
Sami Tolvanen <samitolvanen@google.com>,
Kees Cook <keescook@chromium.org>
Subject: [PATCH v2 1/2] arm64: Always load shadow stack pointer directly from the task struct
Date: Mon, 9 Jan 2023 18:47:59 +0100 [thread overview]
Message-ID: <20230109174800.3286265-2-ardb@kernel.org> (raw)
In-Reply-To: <20230109174800.3286265-1-ardb@kernel.org>
All occurrences of the scs_load macro load the value of the shadow call
stack pointer from the task which is current at that point. So instead
of taking a task struct register argument in the scs_load macro to
specify the task struct to load from, let's always reference the current
task directly. This should make it much harder to exploit any
instruction sequences reloading the shadow call stack pointer register
from memory.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/include/asm/scs.h | 7 ++++---
arch/arm64/kernel/entry.S | 4 ++--
arch/arm64/kernel/head.S | 2 +-
3 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h
index ff7da1268a52ab79..13df982a080805e6 100644
--- a/arch/arm64/include/asm/scs.h
+++ b/arch/arm64/include/asm/scs.h
@@ -10,15 +10,16 @@
#ifdef CONFIG_SHADOW_CALL_STACK
scs_sp .req x18
- .macro scs_load tsk
- ldr scs_sp, [\tsk, #TSK_TI_SCS_SP]
+ .macro scs_load_current
+ get_current_task scs_sp
+ ldr scs_sp, [scs_sp, #TSK_TI_SCS_SP]
.endm
.macro scs_save tsk
str scs_sp, [\tsk, #TSK_TI_SCS_SP]
.endm
#else
- .macro scs_load tsk
+ .macro scs_load_current
.endm
.macro scs_save tsk
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 11cb99c4d298784d..546f7773238ea45d 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -275,7 +275,7 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
alternative_else_nop_endif
1:
- scs_load tsk
+ scs_load_current
.else
add x21, sp, #PT_REGS_SIZE
get_current_task tsk
@@ -848,7 +848,7 @@ SYM_FUNC_START(cpu_switch_to)
msr sp_el0, x1
ptrauth_keys_install_kernel x1, x8, x9, x10
scs_save x0
- scs_load x1
+ scs_load_current
ret
SYM_FUNC_END(cpu_switch_to)
NOKPROBE(cpu_switch_to)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 952e17bd1c0b4f91..b9c1a506798ea315 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -404,7 +404,7 @@ SYM_FUNC_END(create_kernel_mapping)
stp xzr, xzr, [sp, #S_STACKFRAME]
add x29, sp, #S_STACKFRAME
- scs_load \tsk
+ scs_load_current
adr_l \tmp1, __per_cpu_offset
ldr w\tmp2, [\tsk, #TSK_TI_CPU]
--
2.39.0
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2023-01-09 17:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 17:47 [PATCH v2 0/2] arm64: harden shadow call stack pointer handling Ard Biesheuvel
2023-01-09 17:47 ` Ard Biesheuvel [this message]
2023-01-10 14:55 ` [PATCH v2 1/2] arm64: Always load shadow stack pointer directly from the task struct Mark Rutland
2023-01-12 22:18 ` Kees Cook
2023-01-09 17:48 ` [PATCH v2 2/2] arm64: Stash shadow stack pointer in the task struct on interrupt Ard Biesheuvel
2023-01-10 14:57 ` Mark Rutland
2023-01-12 22:18 ` Kees Cook
2023-01-20 16:59 ` [PATCH v2 0/2] arm64: harden shadow call stack pointer handling Catalin Marinas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230109174800.3286265-2-ardb@kernel.org \
--to=ardb@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=keescook@chromium.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=samitolvanen@google.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).