Re: [PATCH] SquashFS, XZ: Don't use uninitialized variable in squashfs_xz_uncompress

From: Phillip Lougher
Date: Mon Jan 24 2011 - 18:31:00 EST

On 24/01/11 22:43, Andrew Morton wrote:
On Thu, 20 Jan 2011 21:53:23 +0100 (CET)
Jesper Juhl<jj@xxxxxxxxxxxxx> wrote:

In fs/squashfs/xz_wrapper.c::squashfs_xz_uncompress() we have this code:

enum xz_ret xz_err;
do {
if (stream->buf.in_pos == stream->buf.in_size&& k< b) {
... [nothing that assigns to 'xz_err'] ...
if (avail == 0) {
offset = 0;

hm, maybe. The handling of the `avail == 0' case looks odd. It sits
there in a loop doing wait_on_buffer() against buffers which it will
never use and possible reporting -EIO for a buffer which it didn't use,
which seems bogus.

Hi Andrew,

I'm just about to send out a patch that fixes this uninitialised variable
bug by way of getting rid of that if (avail == 0) case.

The avail == 0 case is a workaround for the fact that the caller code
can occasionally pass a buffer head that has already been
consumed (read offset into buffer head is at the end of the buffer).


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