[PATCH 3.15 59/66] lz4: add overrun checks to lz4_uncompress_unknownoutputsize()

Greg Kroah-Hartman
2014-07-04T22:55:24Z

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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@suse.com>
Cc: "Don A. Bailey" <donb@securitymouse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
lib/lz4/lz4_decompress.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@@ -192,6 +192,8 @@ static int lz4_uncompress_unknownoutputs
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_unknownoutputs
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_unknownoutputs

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

int lz4_decompress(const unsigned char *src, size_t *src_len,