Re: mm/slab: ppc: ubi: kmalloc_slab WARNING / PPC + UBI driver

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Mon, 2013-08-12 at 13:06 +0200, Wladislav Wiebe wrote:
> Hi guys,
> 
> we got the real root cause of the allocation issue:
> 
> Subject: [PATCH 1/1] of: fdt: fix memory initialization for expanded DT
> 
> Already existing property flags are filled wrong for properties created from
> initial FDT. This could cause problems if this DYNAMIC device-tree functions
> are used later, i.e. properties are attached/detached/replaced. Simply dumping
> flags from the running system show, that some initial static (not allocated via
> kzmalloc()) nodes are marked as dynamic.

This should go into stable as well...

> I putted some debug extensions to property_proc_show(..) :
> ..
> +       if (OF_IS_DYNAMIC(pp))
> +               pr_err("DEBUG: xxx : OF_IS_DYNAMIC\n");
> +       if (OF_IS_DETACHED(pp))
> +               pr_err("DEBUG: xxx : OF_IS_DETACHED\n");
> 
> when you operate on the nodes (e.g.: ~$ cat /proc/device-tree/*some_node*) you
> will see that those flags are filled wrong, basically in most cases it will dump
> a DYNAMIC or DETACHED status, which is in not true.
> (BTW. this OF_IS_DETACHED is a own define for debug purposes which which just
> make a test_bit(OF_DETACHED, &x->_flags)
> 
> If nodes are dynamic kernel is allowed to kfree() them. But it will crash
> attempting to do so on the nodes from FDT -- they are not allocated via
> kzmalloc().
> 
> Signed-off-by: Wladislav Wiebe <wladislav.kw@gmail.com>
> ---
>  drivers/of/fdt.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 6bb7cf2..b10ba00 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -392,6 +392,8 @@ static void __unflatten_device_tree(struct boot_param_header *blob,
>  	mem = (unsigned long)
>  		dt_alloc(size + 4, __alignof__(struct device_node));
> 
> +	memset((void *)mem, 0, size);
> +
>  	((__be32 *)mem)[size / 4] = cpu_to_be32(0xdeadbeef);
> 
>  	pr_debug("  unflattening %lx...\n", mem);
> -- 1.7.1
> 
> This is committed to the mainline - hope it comes in soon.
> 
> Thanks & BR,
> Wladislav Wiebe
> 
> 
> On 31/07/13 19:34, Aaro Koskinen wrote:
> > Hi,
> > 
> > On Wed, Jul 31, 2013 at 01:42:31PM +0200, Wladislav Wiebe wrote:
> >> DEBUG: xxx kmalloc_slab, requested 'size' = 8388608, KMALLOC_MAX_SIZE = 4194304
> > [...]
> >> [ccd3be60] [c0099fd4] kmalloc_slab+0x48/0xe8 (unreliable)
> >> [ccd3be70] [c00ae650] __kmalloc+0x20/0x1b4
> >> [ccd3be90] [c00d46f4] seq_read+0x2a4/0x540
> >> [ccd3bee0] [c00fe09c] proc_reg_read+0x5c/0x90
> >> [ccd3bef0] [c00b4e1c] vfs_read+0xa4/0x150
> >> [ccd3bf10] [c00b500c] SyS_read+0x4c/0x84
> >> [ccd3bf40] [c000be80] ret_from_syscall+0x0/0x3c
> > 
> > It seems some procfs file is trying to dump 8 MB at a single go. You
> > need to fix that to return data in smaller chunks. What file is it?
> > 
> > A.
> > 
> 
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> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev


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