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

["Dan Kruchinin" <dubalom@gmail.com>]

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.

--------------
diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index bfb3731..4db6b21 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -185,7 +185,10 @@ static int usb_parse_interface(struct device
*ddev, int cfgno,
		num_ep = USB_MAXENDPOINTS;
	}

-	len = sizeof(struct usb_host_endpoint) * num_ep;
+	len = sizeof(struct usb_host_endpoint);
+	if (num_ep > 0)
+	  len *= num_ep;
+	
	alt->endpoint = kzalloc(len, GFP_KERNEL);
	if (!alt->endpoint)
		return -ENOMEM;
---------------

Dan Kruchinin.
-
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