[3.13.y-ckt stable] Patch "tracing: Fix unmapping loop in tracing_mark_write" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Tue Mar 31 18:46:03 UTC 2015

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

    tracing: Fix unmapping loop in tracing_mark_write

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:


This patch is scheduled to be released in version 3.13.11-ckt18.

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

For more information about the 3.13.y-ckt tree, see



>From 191ef396e72bc095fe819ec8e62e208e04c51b72 Mon Sep 17 00:00:00 2001
From: Vikram Mulukutla <markivx at codeaurora.org>
Date: Wed, 17 Dec 2014 18:50:56 -0800
Subject: tracing: Fix unmapping loop in tracing_mark_write

commit 7215853e985a4bef1a6c14e00e89dfec84f1e457 upstream.

Commit 6edb2a8a385f0cdef51dae37ff23e74d76d8a6ce introduced
an array map_pages that contains the addresses returned by
kmap_atomic. However, when unmapping those pages, map_pages[0]
is unmapped before map_pages[1], breaking the nesting requirement
as specified in the documentation for kmap_atomic/kunmap_atomic.

This was caught by the highmem debug code present in kunmap_atomic.
Fix the loop to do the unmapping properly.

Link: http://lkml.kernel.org/r/1418871056-6614-1-git-send-email-markivx@codeaurora.org

Reviewed-by: Stephen Boyd <sboyd at codeaurora.org>
Reported-by: Lime Yang <limey at codeaurora.org>
Signed-off-by: Vikram Mulukutla <markivx at codeaurora.org>
Signed-off-by: Steven Rostedt <rostedt at goodmis.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
 kernel/trace/trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 111cc34..bc88bc2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4604,7 +4604,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
 	*fpos += written;

-	for (i = 0; i < nr_pages; i++){
+	for (i = nr_pages - 1; i >= 0; i--) {

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