usb: gadget: f_fs: Assorted buffer overflow checks.

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>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 5490fc51638ede3c565eff9036ff3beaf884d3a9..fd80c1b9c8234cf4de8371c7ca4e528bc4712fc3 100644 (file)
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2269,6 +2269,8 @@ static int __ffs_data_do_os_desc(enum ffs_os_desc_type type,
                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) {
@@ -2277,6 +2279,11 @@ static int __ffs_data_do_os_desc(enum ffs_os_desc_type type,
                        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",
@@ -2363,6 +2370,9 @@ static int __ffs_data_got_descs(struct ffs_data *ffs,
                }
        }
        if (flags & (1 << i)) {
+               if (len < 4) {
+                       goto error;
+               }
                os_descs_count = get_unaligned_le32(data);
                data += 4;
                len -= 4;
@@ -2435,7 +2445,8 @@ static int __ffs_data_got_strings(struct ffs_data *ffs,
 
        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);