[PATCH 4.4 26/29] usb: gadget: f_fs: Assorted buffer overflow checks.

Greg Kroah-Hartman
2017-02-07T12:47:02Z

From: Vincent Pelletier <plr.vincent@gmail.com>

commit 83e526f2a2fa4b2e82b6bd3ddbb26b70acfa8947 upstream.

OS descriptor head, when flagged as provided, is accessed without
checking if it fits in provided buffer. Verify length before access.
Also, there are other places where buffer length it checked
after accessing offsets which are potentially past the end. Check
buffer length before as well to fail cleanly.

Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/gadget/function/f_fs.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2079,6 +2079,8 @@ static int __ffs_data_do_os_desc(enum ff
if (len < sizeof(*d) || h->interface >= ffs->interfaces_count)
return -EINVAL;
length = le32_to_cpu(d->dwSize);
+ if (len < length)
+ return -EINVAL;
type = le32_to_cpu(d->dwPropertyDataType);
if (type < USB_EXT_PROP_UNICODE ||
type > USB_EXT_PROP_UNICODE_MULTI) {
@@ -2087,6 +2089,11 @@ static int __ffs_data_do_os_desc(enum ff
return -EINVAL;
}
pnl = le16_to_cpu(d->wPropertyNameLength);
+ if (length < 14 + pnl) {
+ pr_vdebug("invalid os descriptor length: %d pnl:%d (descriptor %d)\n",
+ length, pnl, type);
+ return -EINVAL;
+ }
pdl = le32_to_cpu(*(u32 *)((u8 *)data + 10 + pnl));
if (length != 14 + pnl + pdl) {
pr_vdebug("invalid os descriptor length: %d pnl:%d pdl:%d (descriptor %d)\n",
@@ -2171,6 +2178,9 @@ static int __ffs_data_got_descs(struct f
}
}
if (flags & (1 << i)) {
+ if (len < 4) {
+ goto error;
+ }
os_descs_count = get_unaligned_le32(data);
data += 4;
len -= 4;
@@ -2243,7 +2253,8 @@ static int __ffs_data_got_strings(struct

ENTER();

- if (unlikely(get_unaligned_le32(data) != FUNCTIONFS_STRINGS_MAGIC ||
+ if (unlikely(len < 16 ||
+ get_unaligned_le32(data) != FUNCTIONFS_STRINGS_MAGIC ||
get_unaligned_le32(data + 4) != len))
goto error;
str_count = get_unaligned_le32(data + 8);