[3.16.y-ckt stable] Patch "powerpc/perf: Cap 64bit userspace backtraces to PERF_MAX_STACK_DEPTH" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    powerpc/perf: Cap 64bit userspace backtraces to PERF_MAX_STACK_DEPTH

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt11.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 1564ecf19e3b5e92b48531d580c3da04131596d5 Mon Sep 17 00:00:00 2001
From: Anton Blanchard <anton at samba.org>
Date: Tue, 14 Apr 2015 07:51:03 +1000
Subject: powerpc/perf: Cap 64bit userspace backtraces to PERF_MAX_STACK_DEPTH

commit 9a5cbce421a283e6aea3c4007f141735bf9da8c3 upstream.

We cap 32bit userspace backtraces to PERF_MAX_STACK_DEPTH
(currently 127), but we forgot to do the same for 64bit backtraces.

Signed-off-by: Anton Blanchard <anton at samba.org>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/powerpc/perf/callchain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index 2396dda282cd..ead55351b254 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c
@@ -243,7 +243,7 @@ static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 	sp = regs->gpr[1];
 	perf_callchain_store(entry, next_ip);

-	for (;;) {
+	while (entry->nr < PERF_MAX_STACK_DEPTH) {
 		fp = (unsigned long __user *) sp;
 		if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 			return;