[Bug 30872] Calling kfree() for uninitialized pointer in ext4_mb_init_backend()

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=30872


Eric Sandeen <sandeen@redhat.com> changed:

           What    |Removed                     |Added
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                 CC|                            |sandeen@redhat.com




--- Comment #2 from Eric Sandeen <sandeen@redhat.com>  2011-03-14 14:23:29 ---
(In reply to comment #1)

...

> > If ext4_mb_add_groupinfo() fails for some reason (e.g. if memory allocation at
> > line 2296 fails), ext4_mb_init_backend() tries to call kfree() for each
> > element in sbi->s_group_info array, including the ones that have not been
> > initialized yet:
> >
> > fs/ext4/mballoc.c:2414:
> > err_freebuddy:
> >    cachep = get_groupinfo_cache(sb->s_blocksize_bits);
> >    while (i-- > 0)
> >        kmem_cache_free(cachep, ext4_get_group_info(sb, i));
> >    i = num_meta_group_infos;
> >    while (i-- > 0)
> 
> literally understand, should be
> while (--i >= 0)
> 
> Could you try with above?

Hm, that probably is the most direct fix.

I sent a patch here:
http://marc.info/?l=linux-ext4&m=129979820301087&w=2
which initializes all the pointers to NULL and only frees if they are non-NULL, 
which may be more foolproof, but might also be overkill.

-Eric

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