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[PATCH] xfsprogs: libxfs: Don't forget to initialize the radix tree subs

To: xfs@xxxxxxxxxxx
Subject: [PATCH] xfsprogs: libxfs: Don't forget to initialize the radix tree subsystem
From: Alex Elder <aelder@xxxxxxx>
Date: Thu, 13 Oct 2011 13:50:14 -0500
User-agent: Heirloom mailx 12.5 7/5/10
The libxfs code uses radix tree routines to manage a mount
point's m_perag_tree.  But the radix tree routines assume
that radix_tree_init() has been called to initialize the
height_to_maxindex[] global array, and this was not being
done.

This showed up when running mkfs.xfs on an ia64 system.  Since
it wasn't initialized, the array was filled with zeroes.  The
first time radix_tree_extend() got called (with index 0), the
height would be set to 1 and all would seem fine.

The *second* time it got called (with index 1) a problem would
arise--though we were apparently "lucky" enough for it not to
matter.  The following loop would simply reference invalid slots
beyond the end of the array until it happened upon one that was
non-zero.  (I've expanded the function radix_tree_maxindex() here.)

        /* Figure out what the height should be.  */
        height = root->height + 1;
        while (index > height_to_maxindex[height])
                height++;

As an example, this looped 1937 times before it found a non-zere
value that would cause it to break out of the loop.

Even that *seemed* to be OK.  But at the end of mkfs.xfs, when
it calls libxfs_umount(), non-initialized "slots" are dereferenced
and we hit a fault.

Wow.

Signed-off-by: Alex Elder <aelder@xxxxxxx>

---
 libxfs/init.c |    2 ++
 1 file changed, 2 insertions(+)

Index: b/libxfs/init.c
===================================================================
--- a/libxfs/init.c
+++ b/libxfs/init.c
@@ -249,6 +249,8 @@ libxfs_init(libxfs_init_t *a)
        fd = -1;
        flags = (a->isreadonly | a->isdirect);
 
+       radix_tree_init();
+
        if (a->volname) {
                if(!check_open(a->volname,flags,&rawfile,&blockfile))
                        goto done;

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