Re: [PATCH -mm] drivers/usb/core/config.c: kzalloc(0,..)

[Greg KH <greg@kroah.com>]

On Tue, May 08, 2007 at 07:03:08AM +0400, Dan Kruchinin wrote:
>  The following patch fixes such SLUB report(when someone tries to
>  allocate 0 bytes):
>  --
>  May  8 00:19:15 midgard kernel: [   21.933467] BUG: at
>  include/linux/slub_def.h:88 kmalloc_index()
>  May  8 00:19:15 midgard kernel: [   21.933470]
>  [show_registers+410/736] show_trace_log_lvl+0x1a/0x30
>  May  8 00:19:15 midgard kernel: [   21.933478]
>  [print_trace_warning_symbol+50/64] show_trace+0x12/0x20
>  May  8 00:19:15 midgard kernel: [   21.933482]  [fixup_irqs+38/192]
>  dump_stack+0x16/0x20
>  May  8 00:19:15 midgard kernel: [   21.933485]  [do_lookup+195/400]
>  get_slab+0x213/0x230
>  May  8 00:19:15 midgard kernel: [   21.933489]  [do_lookup+309/400]
>  __kmalloc_track_caller+0x15/0x40
>  May  8 00:19:15 midgard kernel: [   21.933493]  [__vunmap+25/240]
>  __kzalloc+0x19/0x50
>  May  8 00:19:15 midgard kernel: [   21.933498]  [<df05778e>]
>  usb_parse_configuration+0x85e/0xe70 [usbcore]
>  May  8 00:19:15 midgard kernel: [   21.933520]  [<df057fcb>]
>  usb_get_configuration+0x12b/0x450 [usbcore]
>  May  8 00:19:15 midgard kernel: [   21.933535]  [<df04ed87>]
>  usb_new_device+0x17/0x1c0 [usbcore]
>  May  8 00:19:15 midgard kernel: [   21.933550]  [<df05073a>]
>  hub_thread+0x79a/0xfd0 [usbcore]
>  May  8 00:19:15 midgard kernel: [   21.933564]
>  [run_posix_cpu_timers+1218/2064] kthread+0x42/0x70
>  May  8 00:19:15 midgard kernel: [   21.933569]  [math_error+87/240]
>  kernel_thread_helper+0x7/0x10
>  May  8 00:19:15 midgard kernel: [   21.933572]  =======================
>  --
> 
>  The problem was in drivers/usb/core/config.c in function 
>  usb_parse_interface:
>  ---
>  num_ep = num_ep_orig = alt->desc.bNumEndpoints;
>  ...
>  len = sizeof(struct usb_host_endpoint) * num_ep;
>  alt->endpoint = kzalloc(len, GFP_KERNEL);
>  ---
> 
>  num_ep can be 0, as it was in my case, so following patch makes this
>  situation more obvious
>  and clear.

Well, the whitespace was damaged, but the idea looks sane.  Care to
respin this?

However, what kind of device do you have that you have no endpoints for
an interface?  Why have the interface then?

thanks,

greg k-h