linux-kernel - [tip: core/rseq] s390/uaccess: Use unsafe wrappers for ASM GOTO

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Message-ID: <176173345017.2601451.5300987106730295859.tip-bot2@tip-bot2>
Date: Wed, 29 Oct 2025 10:24:10 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Heiko Carstens <hca@...ux.ibm.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: core/rseq] s390/uaccess: Use unsafe wrappers for ASM GOTO

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     6c5957fa71461c088a95df7772e640ab8b1e3bf3
Gitweb:        https://git.kernel.org/tip/6c5957fa71461c088a95df7772e640ab8b1e3bf3
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:43:52 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 29 Oct 2025 11:07:09 +01:00

s390/uaccess: Use unsafe wrappers for ASM GOTO

ASM GOTO is miscompiled by GCC when it is used inside a auto cleanup scope:

bool foo(u32 __user *p, u32 val)
{
	scoped_guard(pagefault)
		unsafe_put_user(val, p, efault);
	return true;
efault:
	return false;
}

It ends up leaking the pagefault disable counter in the fault path. clang
at least fails the build.

S390 is not affected for unsafe_*_user() as it uses its own local label
already, but __get/put_kernel_nofault() lack that.

Rename them to arch_*_kernel_nofault() which makes the generic uaccess
header wrap it with a local label that makes both compilers emit correct
code.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Acked-by: Heiko Carstens <hca@...ux.ibm.com>
Link: https://patch.msgid.link/20251027083745.483079889@linutronix.de
---
 arch/s390/include/asm/uaccess.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index 3e5b8b6..c5e02ad 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -468,8 +468,8 @@ do {									\
 
 #endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT && CONFIG_CC_HAS_ASM_AOR_FORMAT_FLAGS */
 
-#define __get_kernel_nofault __mvc_kernel_nofault
-#define __put_kernel_nofault __mvc_kernel_nofault
+#define arch_get_kernel_nofault __mvc_kernel_nofault
+#define arch_put_kernel_nofault __mvc_kernel_nofault
 
 void __cmpxchg_user_key_called_with_bad_pointer(void);