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Re: [augeas-devel] libguestfs crash in libaugeas



On Tue, Aug 03, 2010 at 11:11:57AM -0700, David Lutterkort wrote:
> On Tue, 2010-08-03 at 11:54 +0100, Matthew Booth wrote:
> > We're having a problem with libguestfs's daemon crashing during v2v. The 
> > crash is in libaugeas. We unfortunately don't have a small reproducer, 
> > but we have finally managed to get a core dump. The stack trace looks 
> > like this:
> > 
> > #0  0x00007fb490f3763b in pathx_symtab_remove_descendants (
> >      symtab=<value optimized out>, tree=0x5941900) at pathx.c:2569
> > #1  0x00007fb490f3580b in tree_rm (p=0x8177da0) at augeas.c:890
> > #2  0x00007fb490f363e5 in aug_rm (aug=0x57b5e20, path=<value optimized out>)
> >      at augeas.c:911
> > #3  0x00007fb490f36b08 in aug_save (aug=0x57b5e20) at augeas.c:1192
> > #4  0x0000000000403992 in do_aug_save () at augeas.c:332
> > #5  0x000000000042194f in aug_save_stub (xdr_in=<value optimized out>)
> >      at stubs.c:623
> > 
> > Interesting local variables:
> > 
> > (gdb) print t
> > $4 = (struct tree *) 0xc1
> > (gdb) print *tree
> > $5 = {next = 0x0, parent = 0x66a5130, label = 0x64f55a0 "saved",
> >    children = 0x0, value = 0x6a32290 "/files/boot/grub/menu.lst", dirty = 0}
> > 
> > This is augeas-libs-0.7.2-3.fc13.x86_64.
> 
> Looks like memory is getting corrupted before things blow up here. More
> specifically, the nodeset for a variable has been corrupted. What's in
> tab->name ? (That's the name of the variable)
> 
> > There are many circumstances in which this conversion works. For 
> > example, if I run the conversion again against the partially converted 
> > guest it will succeed. This leads me to believe that the problem is 
> > unlikely to be local to the crash.
> > 
> > Any ideas? I can provide the crashed daemon and core dump for inspection 
> > if required. I'm also more than happy to test augeas patches.
> 
> The following would be really useful in putting together a reproducer
> with augtool, not sure how realistic getting that is:
> 
>       * A list of the augeas commands that have been executed since the
>         last call to aug_init up to the point of the crash
>       * A tarball of /etc of the image that causes the crash
>       * A list of the defined variables if we can't get a list of
>         commands - you can get them with 'aug_print(aug,
>         "/augeas/variables")' just before the aug_save call that blows
>         up.

David, you mentioned in another email that there is a variable "new".

Indeed, virt-v2v defines this:

        $g->aug_defnode('new',
                        '/files/boot/grub/menu.lst/title[last()+1]',
                        $title);

from:
http://git.fedorahosted.org/git/?p=virt-v2v.git;a=blob;f=lib/Sys/VirtV2V/GuestOS/RedHat.pm;h=101a64b63b38c5e965a0e5ae34404679de059403;hb=HEAD#l975

I hope Matt is able to provide the other details you requested
tomorrow.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://et.redhat.com/~rjones/libguestfs/
See what it can do: http://et.redhat.com/~rjones/libguestfs/recipes.html


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