FAILED: patch "[PATCH] s390/stackleak: Fix __stackleak_poison() inline assembly" failed to apply to 6.12-stable tree

FAILED: patch "[PATCH] s390/stackleak: Fix __stackleak_poison() inline assembly" failed to apply to 6.12-stable tree

[gregkh]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 674c5ff0f440a051ebf299d29a4c013133d81a65
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026031738-blob-labored-5201@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 674c5ff0f440a051ebf299d29a4c013133d81a65 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <hca@linux.ibm.com>
Date: Mon, 2 Mar 2026 14:35:00 +0100
Subject: [PATCH] s390/stackleak: Fix __stackleak_poison() inline assembly
 constraint

The __stackleak_poison() inline assembly comes with a "count" operand where
the "d" constraint is used. "count" is used with the exrl instruction and
"d" means that the compiler may allocate any register from 0 to 15.

If the compiler would allocate register 0 then the exrl instruction would
not or the value of "count" into the executed instruction - resulting in a
stackframe which is only partially poisoned.

Use the correct "a" constraint, which excludes register 0 from register
allocation.

Fixes: 2a405f6bb3a5 ("s390/stackleak: provide fast __stackleak_poison() implementation")
Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20260302133500.1560531-4-hca@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index cc187afa07b3..78195ee5e99f 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -159,7 +159,7 @@ static __always_inline void __stackleak_poison(unsigned long erase_low,
 		"	j	4f\n"
 		"3:	mvc	8(1,%[addr]),0(%[addr])\n"
 		"4:"
-		: [addr] "+&a" (erase_low), [count] "+&d" (count), [tmp] "=&a" (tmp)
+		: [addr] "+&a" (erase_low), [count] "+&a" (count), [tmp] "=&a" (tmp)
 		: [poison] "d" (poison)
 		: "memory", "cc"
 		);

[PATCH 6.12.y] s390/stackleak: Fix __stackleak_poison() inline assembly constraint

[Heiko Carstens]

The __stackleak_poison() inline assembly comes with a "count" operand where
the "d" constraint is used. "count" is used with the exrl instruction and
"d" means that the compiler may allocate any register from 0 to 15.

If the compiler would allocate register 0 then the exrl instruction would
not or the value of "count" into the executed instruction - resulting in a
stackframe which is only partially poisoned.

Use the correct "a" constraint, which excludes register 0 from register
allocation.

Fixes: 2a405f6bb3a5 ("s390/stackleak: provide fast __stackleak_poison() implementation")
Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20260302133500.1560531-4-hca@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
(cherry picked from commit 674c5ff0f440a051ebf299d29a4c013133d81a65)
---
 arch/s390/include/asm/processor.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 21ae93cbd8e4..ef622c3f88e5 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -168,7 +168,7 @@ static __always_inline void __stackleak_poison(unsigned long erase_low,
 		"	j	4f\n"
 		"3:	mvc	8(1,%[addr]),0(%[addr])\n"
 		"4:\n"
-		: [addr] "+&a" (erase_low), [count] "+&d" (count), [tmp] "=&a" (tmp)
+		: [addr] "+&a" (erase_low), [count] "+&a" (count), [tmp] "=&a" (tmp)
 		: [poison] "d" (poison)
 		: "memory", "cc"
 		);
-- 
2.51.0