linux-kernel - [PATCH] usb: gadget: f_fs: Fix kernel panic for SuperSpeed

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Date:	Fri, 22 Apr 2016 18:43:00 +0800
From:	Jim Lin <jilin@...dia.com>
To:	<balbi@...nel.org>
CC:	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Jim Lin <jilin@...dia.com>
Subject: [PATCH] usb: gadget: f_fs: Fix kernel panic for SuperSpeed

Android N adds os_desc_compat in v2_descriptor by init_functionfs()
(system/core/adb/usb_linux_client.cpp) to support automatic install
of MTP driver on Windows for USB device mode.

Current __ffs_data_do_os_desc() of f_fs.c will check reserved1 field
and return -EINVAL.
This results in a second adb_write of usb_linux_client.cpp
(system/core/adb/) which doesn't have ss_descriptors filled.
Then later kernel_panic (composite.c) occurs when ss_descriptors
as a pointer with NULL is being accessed.

Fix is to ignore the checking on reserved1 field so that first
adb_write goes successfully with v2_descriptor which has
ss_descriptors filled.

Signed-off-by: Jim Lin <jilin@...dia.com>
---
 drivers/usb/gadget/function/f_fs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 73515d5..f5ea3df 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2050,8 +2050,7 @@ static int __ffs_data_do_os_desc(enum ffs_os_desc_type type,
 		int i;

 		if (len < sizeof(*d) ||
-		    d->bFirstInterfaceNumber >= ffs->interfaces_count ||
-		    d->Reserved1)
+		    d->bFirstInterfaceNumber >= ffs->interfaces_count)
 			return -EINVAL;
 		for (i = 0; i < ARRAY_SIZE(d->Reserved2); ++i)
 			if (d->Reserved2[i])
-- 
1.9.1