The patch below does not apply to the 3.7-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From db04328c167ff8e7c57f4a3532214aeada3a82fd Mon Sep 17 00:00:00 2001
From: Mark Brown <[email protected]>
Date: Tue, 11 Dec 2012 01:14:11 +0900
Subject: [PATCH] regmap: debugfs: Avoid overflows for very small reads

If count is less than the size of a register then we may hit integer
wraparound when trying to move backwards to check if we're still in
the buffer. Instead move the position forwards to check if it's still
in the buffer, we are unlikely to be able to allocate a buffer
sufficiently big to overflow here.

Signed-off-by: Mark Brown <[email protected]>
Cc: [email protected]

diff --git a/drivers/base/regmap/regmap-debugfs.c 
b/drivers/base/regmap/regmap-debugfs.c
index 00fbd58..3df274e 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -93,7 +93,7 @@ static ssize_t regmap_read_debugfs(struct regmap *map, 
unsigned int from,
                /* If we're in the region the user is trying to read */
                if (p >= *ppos) {
                        /* ...but not beyond it */
-                       if (buf_pos >= count - 1 - map->debugfs_tot_len)
+                       if (buf_pos + 1 + map->debugfs_tot_len >= count)
                                break;
 
                        /* Format the register */

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