Patch "powerpc/kprobes: Dereference function pointers only if the address does not belong to kernel text" has been added to the 4.13-stable tree

[<gregkh@linuxfoundation.org>]

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

    powerpc/kprobes: Dereference function pointers only if the address does not belong to kernel text

to the 4.13-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:
     powerpc-kprobes-dereference-function-pointers-only-if-the-address-does-not-belong-to-kernel-text.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From e6c4dcb308160115287afd87afb63b5684d75a5b Mon Sep 17 00:00:00 2001
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date: Mon, 30 Oct 2017 20:42:09 +0530
Subject: powerpc/kprobes: Dereference function pointers only if the address does not belong to kernel text

From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

commit e6c4dcb308160115287afd87afb63b5684d75a5b upstream.

This makes the changes introduced in commit 83e840c770f2c5
("powerpc64/elfv1: Only dereference function descriptor for non-text
symbols") to be specific to the kprobe subsystem.

We previously changed ppc_function_entry() to always check the provided
address to confirm if it needed to be dereferenced. This is actually
only an issue for kprobe blacklisted asm labels (through use of
_ASM_NOKPROBE_SYMBOL) and can cause other issues with ftrace. Also, the
additional checks are not really necessary for our other uses.

As such, move this check to the kprobes subsystem.

Fixes: 83e840c770f2 ("powerpc64/elfv1: Only dereference function descriptor for non-text symbols")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/kprobes.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -600,7 +600,12 @@ NOKPROBE_SYMBOL(kprobe_fault_handler);
 
 unsigned long arch_deref_entry_point(void *entry)
 {
-	return ppc_global_function_entry(entry);
+#ifdef PPC64_ELF_ABI_v1
+	if (!kernel_text_address((unsigned long)entry))
+		return ppc_global_function_entry(entry);
+	else
+#endif
+		return (unsigned long)entry;
 }
 NOKPROBE_SYMBOL(arch_deref_entry_point);
 


Patches currently in stable-queue which might be from naveen.n.rao@linux.vnet.ibm.com are

queue-4.13/revert-powerpc64-elfv1-only-dereference-function-descriptor-for-non-text-symbols.patch
queue-4.13/powerpc-kprobes-dereference-function-pointers-only-if-the-address-does-not-belong-to-kernel-text.patch