media: pvrusb2: Prevent a buffer overflow

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commit c1ced46c7b 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: 7fb20fa38c ("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>

...

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Dan Carpenter 2019-04-08 05:52:38 -04:00 • committed by Ben Hutchings

parent 1903a2f501

commit 2ffeae7e76

2 changed files with 3 additions and 0 deletions

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drivers/media/usb/pvrusb2/pvrusb2-hdw.c

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drivers/media/usb/pvrusb2/pvrusb2-hdw.h

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