Patch "usb: gadget: f_fs: avoid out of bounds access on comp_desc" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

usb: gadget: f_fs: avoid out of bounds access on comp_desc

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-gadget-f_fs-avoid-out-of-bounds-access-on-comp_desc.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: William Wu <[email protected]>
Date: Tue, 25 Apr 2017 17:45:48 +0800
Subject: usb: gadget: f_fs: avoid out of bounds access on comp_desc

From: William Wu <[email protected]>

commit b7f73850bb4fac1e2209a4dd5e636d39be92f42c upstream.

Companion descriptor is only used for SuperSpeed endpoints, if the endpoints are HighSpeed or FullSpeed, the Companion descriptor will not allocated, so we can only access it if gadget is SuperSpeed.

I can reproduce this issue on Rockchip platform rk3368 SoC which supports USB 2.0, and use functionfs for ADB. Kernel build with CONFIG_KASAN=y and CONFIG_SLUB_DEBUG=y report the following BUG:

==================================================================

BUG: KASAN: slab-out-of-bounds in ffs_func_set_alt+0x224/0x3a0 at addr ffffffc0601f6509
Read of size 1 by task swapper/0/0
============================================================================

BUG kmalloc-256 (Not tainted): kasan: bad access detected
----------------------------------------------------------------------------

Disabling lock debugging due to kernel taint
INFO: Allocated in ffs_func_bind+0x52c/0x99c age=1275 cpu=0 pid=1

alloc_debug_processing+0x128/0x17c
___slab_alloc.constprop.58+0x50c/0x610
__slab_alloc.isra.55.constprop.57+0x24/0x34
__kmalloc+0xe0/0x250
ffs_func_bind+0x52c/0x99c
usb_add_function+0xd8/0x1d4
configfs_composite_bind+0x48c/0x570
udc_bind_to_driver+0x6c/0x170
usb_udc_attach_driver+0xa4/0xd0
gadget_dev_desc_UDC_store+0xcc/0x118
configfs_write_file+0x1a0/0x1f8
__vfs_write+0x64/0x174
vfs_write+0xe4/0x200
SyS_write+0x68/0xc8
el0_svc_naked+0x24/0x28
INFO: Freed in inode_doinit_with_dentry+0x3f0/0x7c4 age=1275 cpu=7 pid=247
...
Call trace:
[<ffffff900808aab4>] dump_backtrace+0x0/0x230
[<ffffff900808acf8>] show_stack+0x14/0x1c
[<ffffff90084ad420>] dump_stack+0xa0/0xc8
[<ffffff90082157cc>] print_trailer+0x188/0x198
[<ffffff9008215948>] object_err+0x3c/0x4c
[<ffffff900821b5ac>] kasan_report+0x324/0x4dc
[<ffffff900821aa38>] __asan_load1+0x24/0x50
[<ffffff90089eb750>] ffs_func_set_alt+0x224/0x3a0
[<ffffff90089d3760>] composite_setup+0xdcc/0x1ac8
[<ffffff90089d7394>] android_setup+0x124/0x1a0
[<ffffff90089acd18>] _setup+0x54/0x74
[<ffffff90089b6b98>] handle_ep0+0x3288/0x4390
[<ffffff90089b9b44>] dwc_otg_pcd_handle_out_ep_intr+0x14dc/0x2ae4
[<ffffff90089be85c>] dwc_otg_pcd_handle_intr+0x1ec/0x298
[<ffffff90089ad680>] dwc_otg_pcd_irq+0x10/0x20
[<ffffff9008116328>] handle_irq_event_percpu+0x124/0x3ac
[<ffffff9008116610>] handle_irq_event+0x60/0xa0
[<ffffff900811af30>] handle_fasteoi_irq+0x10c/0x1d4
[<ffffff9008115568>] generic_handle_irq+0x30/0x40
[<ffffff90081159b4>] __handle_domain_irq+0xac/0xdc
[<ffffff9008080e9c>] gic_handle_irq+0x64/0xa4
...
Memory state around the buggy address:
  ffffffc0601f6400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffffffc0601f6480: 00 00 00 00 00 00 00 00 00 00 06 fc fc fc fc fc
 >ffffffc0601f6500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                       ^
  ffffffc0601f6580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffffffc0601f6600: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================

---
 drivers/usb/gadget/function/f_fs.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

@@ -1859,12 +1859,12 @@ static int ffs_func_eps_enable(struct ff
 		ep->ep->driver_data = ep;
 		ep->ep->desc = ds;
 
-		comp_desc = (struct usb_ss_ep_comp_descriptor *)(ds +
-				USB_DT_ENDPOINT_SIZE);
-		ep->ep->maxburst = comp_desc->bMaxBurst + 1;
-
-		if (needs_comp_desc)
+		if (needs_comp_desc) {
+			comp_desc = (struct usb_ss_ep_comp_descriptor *)(ds +
+					USB_DT_ENDPOINT_SIZE);
+			ep->ep->maxburst = comp_desc->bMaxBurst + 1;
 			ep->ep->comp_desc = comp_desc;
+		}
 
 		ret = usb_ep_enable(ep->ep);
 		if (likely(!ret)) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/usb-gadget-f_fs-avoid-out-of-bounds-access-on-comp_desc.patch