The patch below does not apply to the 6.15-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-6.15.y git checkout FETCH_HEAD git cherry-pick -x 7f8073cfb04a97842fe891ca50dad60afd1e3121 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025062928-revival-saint-3ba2@gregkh' --subject-prefix 'PATCH 6.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 7f8073cfb04a97842fe891ca50dad60afd1e3121 Mon Sep 17 00:00:00 2001 From: Heiko Carstens hca@linux.ibm.com Date: Fri, 13 Jun 2025 17:53:04 +0200 Subject: [PATCH] s390/ptrace: Fix pointer dereferencing in regs_get_kernel_stack_nth()

The recent change which added READ_ONCE_NOCHECK() to read the nth entry from the kernel stack incorrectly dropped dereferencing of the stack pointer in order to read the requested entry.

In result the address of the entry is returned instead of its content.

Dereference the pointer again to fix this.

Reported-by: Will Deacon will@kernel.org Closes: https://lore.kernel.org/r/20250612163331.GA13384@willie-the-truck Fixes: d93a855c31b7 ("s390/ptrace: Avoid KASAN false positives in regs_get_kernel_stack_nth()") Cc: stable@vger.kernel.org Reviewed-by: Alexander Gordeev agordeev@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Alexander Gordeev agordeev@linux.ibm.com

diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h index 62c0ab4a4b9d..0905fa99a31e 100644 --- a/arch/s390/include/asm/ptrace.h +++ b/arch/s390/include/asm/ptrace.h @@ -265,7 +265,7 @@ static __always_inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *r addr = kernel_stack_pointer(regs) + n * sizeof(long); if (!regs_within_kernel_stack(regs, addr)) return 0; - return READ_ONCE_NOCHECK(addr); + return READ_ONCE_NOCHECK(*(unsigned long *)addr); }

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