[PATCH 3.10 21/53] tracing: Fix unmapping loop in tracing_mark_write

From: Greg Kroah-Hartman
Date: Wed Mar 04 2015 - 03:32:04 EST

3.10-stable review patch. If anyone has any objections, please let me know.


From: Vikram Mulukutla <markivx@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx

Reviewed-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Reported-by: Lime Yang <limey@xxxxxxxxxxxxxx>
Signed-off-by: Vikram Mulukutla <markivx@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

kernel/trace/trace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4588,7 +4588,7 @@ tracing_mark_write(struct file *filp, co
*fpos += written;

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

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