Patch "powerpc: Add missing error check to prom_find_boot_cpu()" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    powerpc: Add missing error check to prom_find_boot_cpu()

to the 4.4-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:
     powerpc-add-missing-error-check-to-prom_find_boot_cpu.patch
and it can be found in the queue-4.4 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 af2b7fa17eb92e52b65f96604448ff7a2a89ee99 Mon Sep 17 00:00:00 2001
From: Darren Stevens <darren@stevens-zone.net>
Date: Mon, 23 Jan 2017 19:42:54 +0000
Subject: powerpc: Add missing error check to prom_find_boot_cpu()

From: Darren Stevens <darren@stevens-zone.net>

commit af2b7fa17eb92e52b65f96604448ff7a2a89ee99 upstream.

prom_init.c calls 'instance-to-package' twice, but the return
is not checked during prom_find_boot_cpu(). The result is then
passed to prom_getprop(), which could be PROM_ERROR. Add a return check
to prevent this.

This was found on a pasemi system, where CFE doesn't have a working
'instance-to package' prom call.

Before Commit 5c0484e25ec0 ('powerpc: Endian safe trampoline') the area
around addr 0 was mostly 0's and this doesn't cause a problem. Once the
macro 'FIXUP_ENDIAN' has been added to head_64.S, the low memory area
now has non-zero values, which cause the prom_getprop() call
to hang.

mpe: Also confirmed that under SLOF if 'instance-to-package' did fail
with PROM_ERROR we would crash in SLOF. So the bug is not specific to
CFE, it's just that other open firmwares don't trigger it because they
have a working 'instance-to-package'.

Fixes: 5c0484e25ec0 ("powerpc: Endian safe trampoline")
Signed-off-by: Darren Stevens <darren@stevens-zone.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/kernel/prom_init.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -2664,6 +2664,9 @@ static void __init prom_find_boot_cpu(vo
 
 	cpu_pkg = call_prom("instance-to-package", 1, 1, prom_cpu);
 
+	if (!PHANDLE_VALID(cpu_pkg))
+		return;
+
 	prom_getprop(cpu_pkg, "reg", &rval, sizeof(rval));
 	prom.cpu = be32_to_cpu(rval);
 


Patches currently in stable-queue which might be from darren@stevens-zone.net are

queue-4.4/powerpc-add-missing-error-check-to-prom_find_boot_cpu.patch