[3.11.y.z extended stable] Patch "lz4: add overrun checks to lz4_uncompress_unknownoutputsize()" has been added to staging queue

[Luis Henriques]

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

    lz4: add overrun checks to lz4_uncompress_unknownoutputsize()

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 88fe9375fb3466b7ce9c61e35c61eb7f78ffbf76 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Date: Thu, 3 Jul 2014 16:06:57 -0700
Subject: lz4: add overrun checks to lz4_uncompress_unknownoutputsize()

commit 4a3a99045177369700c60d074c0e525e8093b0fc upstream.

Jan points out that I forgot to make the needed fixes to the
lz4_uncompress_unknownoutputsize() function to mirror the changes done
in lz4_decompress() with regards to potential pointer overflows.

The only in-kernel user of this function is the zram code, which only
takes data from a valid compressed buffer that it made itself, so it's
not a big issue.  But due to external kernel modules using this
function, it's better to be safe here.

Reported-by: Jan Beulich <JBeulich at suse.com>
Cc: "Don A. Bailey" <donb at securitymouse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 lib/lz4/lz4_decompress.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/lz4/lz4_decompress.c b/lib/lz4/lz4_decompress.c
index 8ee9333e87ae..b6ce2cf35d5d 100644
--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@@ -192,6 +192,8 @@ static int lz4_uncompress_unknownoutputsize(const char *source, char *dest,
 			int s = 255;
 			while ((ip < iend) && (s == 255)) {
 				s = *ip++;
+				if (unlikely(length > (size_t)(length + s)))
+					goto _output_error;
 				length += s;
 			}
 		}
@@ -232,6 +234,8 @@ static int lz4_uncompress_unknownoutputsize(const char *source, char *dest,
 		if (length == ML_MASK) {
 			while (ip < iend) {
 				int s = *ip++;
+				if (unlikely(length > (size_t)(length + s)))
+					goto _output_error;
 				length += s;
 				if (s == 255)
 					continue;
@@ -284,7 +288,7 @@ static int lz4_uncompress_unknownoutputsize(const char *source, char *dest,

 	/* write overflow error detected */
 _output_error:
-	return (int) (-(((char *) ip) - source));
+	return -1;
 }

 int lz4_decompress(const char *src, size_t *src_len, char *dest,
--
1.9.1