media: pvrusb2: Prevent a buffer overflow

commit c1ced46c7b49ad7bc064e68d966e0ad303f917fb upstream.

The ctrl_check_input() function is called from pvr2_ctrl_range_check().
It's supposed to validate user supplied input and return true or false
depending on whether the input is valid or not.  The problem is that
negative shifts or shifts greater than 31 are undefined in C.  In
practice with GCC they result in shift wrapping so this function returns
true for some inputs which are not valid and this could result in a
buffer overflow:

    drivers/media/usb/pvrusb2/pvrusb2-ctrl.c:205 pvr2_ctrl_get_valname()
    warn: uncapped user index 'names[val]'

The cptr->hdw->input_allowed_mask mask is configured in pvr2_hdw_create()
and the highest valid bit is BIT(4).

Fixes: 7fb20fa38caa ("V4L/DVB (7299): pvrusb2: Improve logic which handles input choice availability")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/media/usb/pvrusb2/pvrusb2-hdw.c b/drivers/media/usb/pvrusb2/pvrusb2-hdw.c
index 9623b6218214eb1e5abb6d2336b04a1c8b76ac6d..2f78a4b9f18529a1fa7dbfbdb009de10f9684bf5 100644 (file)
--- a/drivers/media/usb/pvrusb2/pvrusb2-hdw.c
+++ b/drivers/media/usb/pvrusb2/pvrusb2-hdw.c
@@ -670,6 +670,8 @@ static int ctrl_get_input(struct pvr2_ctrl *cptr,int *vp)
 
 static int ctrl_check_input(struct pvr2_ctrl *cptr,int v)
 {
+       if (v < 0 || v > PVR2_CVAL_INPUT_MAX)
+               return 0;
        return ((1 << v) & cptr->hdw->input_allowed_mask) != 0;
 }
 

diff --git a/drivers/media/usb/pvrusb2/pvrusb2-hdw.h b/drivers/media/usb/pvrusb2/pvrusb2-hdw.h
index 41847076f51ac392507f6dec5722f9cc4eb72186..005853a66733233532916c2d50b747ab46a534e3 100644 (file)
--- a/drivers/media/usb/pvrusb2/pvrusb2-hdw.h
+++ b/drivers/media/usb/pvrusb2/pvrusb2-hdw.h
@@ -54,6 +54,7 @@
 #define PVR2_CVAL_INPUT_COMPOSITE 2
 #define PVR2_CVAL_INPUT_SVIDEO 3
 #define PVR2_CVAL_INPUT_RADIO 4
+#define PVR2_CVAL_INPUT_MAX PVR2_CVAL_INPUT_RADIO
 
 enum pvr2_config {
        pvr2_config_empty,    /* No configuration */