linux-kernel - [GIT PULL] x86/shstk change for v6.10

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Message-ID: <ZkHLrqO1HdfQb71Z@gmail.com>
Date: Mon, 13 May 2024 10:13:34 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, the arch/x86 maintainers <x86@...nel.org>,
	"H.J. Lu" <hjl.tools@...il.com>, "H. Peter Anvin" <hpa@...or.com>
Subject: [GIT PULL] x86/shstk change for v6.10

Linus,

Please pull the latest x86/shstk Git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-shstk-2024-05-13

   # HEAD: 2883f01ec37dd8668e7222dfdb5980c86fdfe277 x86/shstk: Enable shadow stacks for x32

Enable shadow stacks for x32.

While we normally don't do such feature-enabling on 32-bit
kernels anymore, this change is small, straightforward & tested on
upstream glibc.

 Thanks,

	Ingo

------------------>
H.J. Lu (1):
      x86/shstk: Enable shadow stacks for x32


 arch/x86/entry/syscalls/syscall_64.tbl | 2 +-
 arch/x86/kernel/shstk.c                | 4 ++--
 arch/x86/kernel/signal_64.c            | 6 ++++++
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 7e8d46f4147f..cc78226ffc35 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -374,7 +374,7 @@
 450	common	set_mempolicy_home_node	sys_set_mempolicy_home_node
 451	common	cachestat		sys_cachestat
 452	common	fchmodat2		sys_fchmodat2
-453	64	map_shadow_stack	sys_map_shadow_stack
+453	common	map_shadow_stack	sys_map_shadow_stack
 454	common	futex_wake		sys_futex_wake
 455	common	futex_wait		sys_futex_wait
 456	common	futex_requeue		sys_futex_requeue
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index 59e15dd8d0f8..6f1e9883f074 100644
--- a/arch/x86/kernel/shstk.c
+++ b/arch/x86/kernel/shstk.c
@@ -163,8 +163,8 @@ static int shstk_setup(void)
 	if (features_enabled(ARCH_SHSTK_SHSTK))
 		return 0;
 
-	/* Also not supported for 32 bit and x32 */
-	if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK) || in_32bit_syscall())
+	/* Also not supported for 32 bit */
+	if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK) || in_ia32_syscall())
 		return -EOPNOTSUPP;
 
 	size = adjust_shstk_size(0);
diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c
index 23d8aaf8d9fd..8a94053c5444 100644
--- a/arch/x86/kernel/signal_64.c
+++ b/arch/x86/kernel/signal_64.c
@@ -315,6 +315,9 @@ int x32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 
 	uc_flags = frame_uc_flags(regs);
 
+	if (setup_signal_shadow_stack(ksig))
+		return -EFAULT;
+
 	if (!user_access_begin(frame, sizeof(*frame)))
 		return -EFAULT;
 
@@ -377,6 +380,9 @@ COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
 	if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 		goto badframe;
 
+	if (restore_signal_shadow_stack())
+		goto badframe;
+
 	if (compat_restore_altstack(&frame->uc.uc_stack))
 		goto badframe;