FAILED: Patch "arm64: poe: fix stale POR_EL0 values for ptrace" failed to apply to 6.12-stable tree

[Sasha Levin]

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 at vger.kernel.org>.

Thanks,
Sasha

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

>From 1f3b950492db411e6c30ee0076b61ef2694c100a Mon Sep 17 00:00:00 2001
From: Joey Gouly <joey.gouly at arm.com>
Date: Tue, 27 Jan 2026 13:39:26 +0000
Subject: [PATCH] arm64: poe: fix stale POR_EL0 values for ptrace

If a process wrote to POR_EL0 and then crashed before a context switch
happened, the coredump would contain an incorrect value for POR_EL0.

The value read in poe_get() would be a stale value left in thread.por_el0.  Fix
this by reading the value from the system register, if the target thread is the
current thread.

This matches what gcs/fpsimd do.

Fixes: 175198199262 ("arm64/ptrace: add support for FEAT_POE")
Reported-by: David Spickett <david.spickett at arm.com>
Cc: stable at vger.kernel.org
Signed-off-by: Joey Gouly <joey.gouly at arm.com>
Cc: Kevin Brodsky <kevin.brodsky at arm.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Reviewed-by: Kevin Brodsky <kevin.brodsky at arm.com>
Acked-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Will Deacon <will at kernel.org>
---
 arch/arm64/kernel/ptrace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index b9bdd83fbbca0..8a14b86cd066c 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1486,6 +1486,9 @@ static int poe_get(struct task_struct *target,
 	if (!system_supports_poe())
 		return -EINVAL;
 
+	if (target == current)
+		current->thread.por_el0 = read_sysreg_s(SYS_POR_EL0);
+
 	return membuf_write(&to, &target->thread.por_el0,
 			    sizeof(target->thread.por_el0));
 }
-- 
2.51.0