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From: Vikram Mulukutla <>
To: Steven Rostedt <>, Ingo Molnar <>
	Lime Yang <>,
	Stephen Boyd <>,
	Vikram Mulukutla <>
Subject: [PATCH] tracing: Fix unmapping loop in tracing_mark_write
Date: Wed, 17 Dec 2014 18:50:56 -0800
Message-ID: <> (raw)

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.

Reviewed-by: Stephen Boyd <>
Reported-by: Lime Yang <>
Signed-off-by: Vikram Mulukutla <>
 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 ab76b7b..bceed34 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4931,7 +4931,7 @@ 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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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-18  2:50 Vikram Mulukutla [this message]
2015-02-09 23:33 ` Stephen Boyd
2015-02-09 23:45   ` Steven Rostedt

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