[PATCH v2 08/31] dib0700_core: don't use stack on I2C reads

[Mauro Carvalho Chehab]

Be sure that I2C reads won't use stack by passing
a pointer to the state buffer, that we know it was
allocated via kmalloc, instead of relying on the buffer
allocated by an I2C client.

Reviewed-By: Patrick Boettcher <patrick.boettc...@posteo.de>
Signed-off-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
---
 drivers/media/usb/dvb-usb/dib0700_core.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb/dib0700_core.c 
b/drivers/media/usb/dvb-usb/dib0700_core.c
index 515f89dba199..92d5408684ac 100644
--- a/drivers/media/usb/dvb-usb/dib0700_core.c
+++ b/drivers/media/usb/dvb-usb/dib0700_core.c
@@ -213,7 +213,7 @@ static int dib0700_i2c_xfer_new(struct i2c_adapter *adap, 
struct i2c_msg *msg,
                                                 usb_rcvctrlpipe(d->udev, 0),
                                                 REQUEST_NEW_I2C_READ,
                                                 USB_TYPE_VENDOR | USB_DIR_IN,
-                                                value, index, msg[i].buf,
+                                                value, index, st->buf,
                                                 msg[i].len,
                                                 USB_CTRL_GET_TIMEOUT);
                        if (result < 0) {
@@ -221,6 +221,14 @@ static int dib0700_i2c_xfer_new(struct i2c_adapter *adap, 
struct i2c_msg *msg,
                                break;
                        }
 
+                       if (msg[i].len > sizeof(st->buf)) {
+                               deb_info("buffer too small to fit %d bytes\n",
+                                        msg[i].len);
+                               return -EIO;
+                       }
+
+                       memcpy(msg[i].buf, st->buf, msg[i].len);
+
                        deb_data("<<< ");
                        debug_dump(msg[i].buf, msg[i].len, deb_data);
 
@@ -238,6 +246,13 @@ static int dib0700_i2c_xfer_new(struct i2c_adapter *adap, 
struct i2c_msg *msg,
                        /* I2C ctrl + FE bus; */
                        st->buf[3] = ((gen_mode << 6) & 0xC0) |
                                 ((bus_mode << 4) & 0x30);
+
+                       if (msg[i].len > sizeof(st->buf) - 4) {
+                               deb_info("i2c message to big: %d\n",
+                                        msg[i].len);
+                               return -EIO;
+                       }
+
                        /* The Actual i2c payload */
                        memcpy(&st->buf[4], msg[i].buf, msg[i].len);
 
@@ -283,6 +298,11 @@ static int dib0700_i2c_xfer_legacy(struct i2c_adapter 
*adap,
                /* fill in the address */
                st->buf[1] = msg[i].addr << 1;
                /* fill the buffer */
+               if (msg[i].len > sizeof(st->buf) - 2) {
+                       deb_info("i2c xfer to big: %d\n",
+                               msg[i].len);
+                       return -EIO;
+               }
                memcpy(&st->buf[2], msg[i].buf, msg[i].len);
 
                /* write/read request */
@@ -299,6 +319,11 @@ static int dib0700_i2c_xfer_legacy(struct i2c_adapter 
*adap,
                                break;
                        }
 
+                       if (msg[i + 1].len > sizeof(st->buf)) {
+                               deb_info("i2c xfer buffer to small for %d\n",
+                                       msg[i].len);
+                               return -EIO;
+                       }
                        memcpy(msg[i + 1].buf, st->buf, msg[i + 1].len);
 
                        msg[i+1].len = len;
-- 
2.7.4


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