Patch "ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed()" has been added to the 5.4-stable tree

This is a note to let you know that I've just added the patch titled

ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed()

to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
arm-9350-1-fault-implement-copy_from_kernel_nofault_allowed.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From 169f9102f9198b04afffa6164372a4ba4070f412 Mon Sep 17 00:00:00 2001
From: Kees Cook <[email protected]>
Date: Thu, 1 Feb 2024 18:32:58 +0100
Subject: ARM: 9350/1: fault: Implement copy_from_kernel_nofault_allowed()

From: Kees Cook <[email protected]>

commit 169f9102f9198b04afffa6164372a4ba4070f412 upstream.

Under PAN emulation when dumping backtraces from things like the LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU) would happen because of dump_instr() attempting to read a userspace address. Make sure copy_from_kernel_nofault() does not attempt this any more.

---
 arch/arm/mm/fault.c |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -25,6 +25,13 @@
 
 #include "fault.h"
 
+bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
+{
+	unsigned long addr = (unsigned long)unsafe_src;
+
+	return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
+}
+
 #ifdef CONFIG_MMU
 
 /*

Patches currently in stable-queue which might be from [email protected] are

queue-5.4/arm-9350-1-fault-implement-copy_from_kernel_nofault_allowed.patch queue-5.4/arm-9351-1-fault-add-cut-here-line-for-prefetch-aborts.patch