Patch "USB: gadgetfs: fix unbounded memory allocation bug" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    USB: gadgetfs: fix unbounded memory allocation bug

to the 4.4-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-gadgetfs-fix-unbounded-memory-allocation-bug.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From faab50984fe6636e616c7cc3d30308ba391d36fd Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Fri, 9 Dec 2016 15:17:46 -0500
Subject: USB: gadgetfs: fix unbounded memory allocation bug

From: Alan Stern <stern@rowland.harvard.edu>

commit faab50984fe6636e616c7cc3d30308ba391d36fd upstream.

Andrey Konovalov reports that fuzz testing with syzkaller causes a
KASAN warning in gadgetfs:

BUG: KASAN: slab-out-of-bounds in dev_config+0x86f/0x1190 at addr ffff88003c47e160
Write of size 65537 by task syz-executor0/6356
CPU: 3 PID: 6356 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #19
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff88003c107ad8 ffffffff81f96aba ffffffff3dc11ef0 1ffff10007820eee
 ffffed0007820ee6 ffff88003dc11f00 0000000041b58ab3 ffffffff8598b4c8
 ffffffff81f96828 ffffffff813fb4a0 ffff88003b6eadc0 ffff88003c107738
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff81f96aba>] dump_stack+0x292/0x398 lib/dump_stack.c:51
 [<ffffffff817e4dec>] kasan_object_err+0x1c/0x70 mm/kasan/report.c:159
 [<     inline     >] print_address_description mm/kasan/report.c:197
 [<ffffffff817e5080>] kasan_report_error+0x1f0/0x4e0 mm/kasan/report.c:286
 [<ffffffff817e5705>] kasan_report+0x35/0x40 mm/kasan/report.c:306
 [<     inline     >] check_memory_region_inline mm/kasan/kasan.c:308
 [<ffffffff817e3fb9>] check_memory_region+0x139/0x190 mm/kasan/kasan.c:315
 [<ffffffff817e4044>] kasan_check_write+0x14/0x20 mm/kasan/kasan.c:326
 [<     inline     >] copy_from_user arch/x86/include/asm/uaccess.h:689
 [<     inline     >] ep0_write drivers/usb/gadget/legacy/inode.c:1135
 [<ffffffff83228caf>] dev_config+0x86f/0x1190 drivers/usb/gadget/legacy/inode.c:1759
 [<ffffffff817fdd55>] __vfs_write+0x5d5/0x760 fs/read_write.c:510
 [<ffffffff817ff650>] vfs_write+0x170/0x4e0 fs/read_write.c:560
 [<     inline     >] SYSC_write fs/read_write.c:607
 [<ffffffff81803a5b>] SyS_write+0xfb/0x230 fs/read_write.c:599
 [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2

Indeed, there is a comment saying that the value of len is restricted
to a 16-bit integer, but the code doesn't actually do this.

This patch fixes the warning.  It replaces the comment with a
computation that forces the amount of data copied from the user in
ep0_write() to be no larger than the wLength size for the control
transfer, which is a 16-bit quantity.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/gadget/legacy/inode.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1125,7 +1125,7 @@ ep0_write (struct file *fd, const char _
 	/* data and/or status stage for control request */
 	} else if (dev->state == STATE_DEV_SETUP) {
 
-		/* IN DATA+STATUS caller makes len <= wLength */
+		len = min_t(size_t, len, dev->setup_wLength);
 		if (dev->setup_in) {
 			retval = setup_req (dev->gadget->ep0, dev->req, len);
 			if (retval == 0) {


Patches currently in stable-queue which might be from stern@rowland.harvard.edu are

queue-4.4/usb-dummy-hcd-fix-bug-in-stop_activity-handle-ep0.patch
queue-4.4/usb-gadgetfs-fix-use-after-free-bug.patch
queue-4.4/usb-gadgetfs-fix-checks-of-wtotallength-in-config-descriptors.patch
queue-4.4/usb-fix-problems-with-duplicate-endpoint-addresses.patch
queue-4.4/usb-gadgetfs-fix-unbounded-memory-allocation-bug.patch