linux-kernel - [PATCH 1/1] usb: gadget: f_fs: Fix kernel panic if use_os

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Date:	Fri, 13 May 2016 20:32:16 +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 1/1] usb: gadget: f_fs: Fix kernel panic if use_os_string not set

If c->cdev->use_os_string flag is not set,
don't need to invoke ffs_do_os_descs() in _ffs_func_bind.
So uninitialized ext_compat_id pointer won't be accessed by
__ffs_func_bind_do_os_desc to cause kernel panic.

Signed-off-by: Jim Lin <jilin@...dia.com>
---
 drivers/usb/gadget/function/f_fs.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 15b648c..af3fdbd 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2851,7 +2851,7 @@ static int _ffs_func_bind(struct usb_configuration *c,
 		goto error;
 
 	func->function.os_desc_table = vla_ptr(vlabuf, d, os_desc_table);
-	if (c->cdev->use_os_string)
+	if (c->cdev->use_os_string) {
 		for (i = 0; i < ffs->interfaces_count; ++i) {
 			struct usb_os_desc *desc;
 
@@ -2862,13 +2862,15 @@ static int _ffs_func_bind(struct usb_configuration *c,
 				vla_ptr(vlabuf, d, ext_compat) + i * 16;
 			INIT_LIST_HEAD(&desc->ext_prop);
 		}
-	ret = ffs_do_os_descs(ffs->ms_os_descs_count,
-			      vla_ptr(vlabuf, d, raw_descs) +
-			      fs_len + hs_len + ss_len,
-			      d_raw_descs__sz - fs_len - hs_len - ss_len,
-			      __ffs_func_bind_do_os_desc, func);
-	if (unlikely(ret < 0))
-		goto error;
+		ret = ffs_do_os_descs(ffs->ms_os_descs_count,
+				      vla_ptr(vlabuf, d, raw_descs) +
+				      fs_len + hs_len + ss_len,
+				      d_raw_descs__sz - fs_len - hs_len -
+				      ss_len,
+				      __ffs_func_bind_do_os_desc, func);
+		if (unlikely(ret < 0))
+			goto error;
+	}
 	func->function.os_desc_n =
 		c->cdev->use_os_string ? ffs->interfaces_count : 0;
 
-- 
1.9.1