Re: [Bug #13112] Oops in drain_array

[Bart]

> On Mon, 27 Apr 2009 13:36:46 -0700 (PDT)
> David Rientjes <rientjes@xxxxxxxxxx> wrote:
>
> > On Mon, 27 Apr 2009, Bart wrote:
> >
> > > After turning the suggested debuging options I've got tons of these when
> > > trying to stress the tape device like before:
> > >
> > > Apr 27 16:57:30 fs kernel: [   96.446708] slab error in verify_redzone_free():
> > > cache `size-128': memory outside object was overwritten
> > > Apr 27 16:57:30 fs kernel: [   96.446713] Pid: 0, comm: swapper Not tainted
> > > 2.6.29.1-64 #2
> > > Apr 27 16:57:30 fs kernel: [   96.446715] Call Trace:
> > > Apr 27 16:57:30 fs kernel: [   96.446717]  <IRQ>  [<ffffffff8029adc5>]
> > > __slab_error+0x1f/0x25
> > > Apr 27 16:57:30 fs kernel: [   96.446728]  [<ffffffff8029b24b>]
> > > cache_free_debugcheck+0x108/0x1d6
> > > Apr 27 16:57:30 fs kernel: [   96.446731]  [<ffffffff8029b473>]
> > > kfree+0x81/0xc2
> > > Apr 27 16:57:30 fs kernel: [   96.446735]  [<ffffffff802bd311>]
> > > bio_free_map_data+0xc/0x1e
> >
> > This appears to be kfree(bmd->iovecs) in bio_free_map_data().  It looks
> > like the memcpy size in bio_set_map_data() overrides the kmalloc size; in
> > other words, for a redzone error, bio->bi_vcnt > nr_pages in
> > bio_copy_user_iov().
>
> Can you try this?
>
> diff --git a/fs/bio.c b/fs/bio.c
> index 7bbc98f..6a09356 100644
> --- a/fs/bio.c
> +++ b/fs/bio.c
> @@ -817,6 +817,9 @@ struct bio *bio_copy_user_iov(struct request_queue *q,
> 		len += iov[i].iov_len;
> 	}
>
> +	if (offset)
> +		nr_pages += 1;
> +
> 	bmd = bio_alloc_map_data(nr_pages, iov_count, gfp_mask);
> 	if (!bmd)
> 		return ERR_PTR(-ENOMEM);

There are no more errors in the dmesg after applying this patch to 
2.6.29.2.

Without this patch I can reproduce this kind of errors on 
2.6.29.1, 2.6.29.2.

I've not tested this patch with 2.6.29.1 and 2.6.30rc3-git3.
I will try to reproduce the error on 2.6.30rc3-git3 as soon as I compile 
it.

--
 Regards
 Bart mmx@xxxxxx
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