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

From: Jim Lin
Date: Fri Apr 22 2016 - 06:43:19 EST

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@xxxxxxxxxx>
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])